WorldWideScience

Sample records for biaxial stress

  1. Reverse loading tests of steel tube under biaxial stress states

    OpenAIRE

    Yanaga, Daisaku; Kuroda, Kouichi; Yaita, Satoshi; Kuwabara, Toshihiko

    2015-01-01

    Biaxial loading and reverse loading tests were performed using seamless carbon steel tubes. Biaxial stress components in the axial and circumferential directions were applied to the tubular specimens using a servo-controlled multiaxial tube expansion testing machine developed by Kuwabara and Sugawara (2013). The tubular specimens were loaded under linear tensile stress paths. Contours of plastic work were measured in the principal stress space, and the differential hardening (DH) behavior was...

  2. Biaxial failure criteria and stress-strain response for concrete of containment structure

    International Nuclear Information System (INIS)

    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, f2/f1=-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

  3. Application of magnetomechanical hysteresis modeling of magnetic techniques for monitoring neutron embrittlement and biaxial stress

    International Nuclear Information System (INIS)

    Research was done on the biaxial stress problem accomplished in the first half of the second year. All of the work done was preparatory to magnetic measurements. Issues addressed were: construction of a model for extracting changes in the magnetic properties of a specimen from the readings of an indirect sensor; initial development of a model for how biaxial stress alters the intrinsic magnetic properties of thespecimen; use of finite element stress analysis modeling to determine a detailed shape for the cruciform biaxial stress specimen; and construction of the biaxial stress loading apparatus

  4. Evaluation of micro fatigue crack growth under equi-biaxial stress by membranous pressure fatigue test

    International Nuclear Information System (INIS)

    For preventing nuclear power plant (NPP) accidents, NPPs are required to ensure system safety in long term safe operation under aging degradation. Now, fatigue accumulation is one of major ageing phenomena and are evaluated to ensure safety by design fatigue curve that are based on the results of uniaxial fatigue tests. On the other hand, thermal stress that occurs in piping of actual components is not uniaxial but equi-biaxial. For accurate evaluation, it is required to conform real circumstance. In this study, membranous pressure fatigue test was conducted to simulated equi-biaxial stress. Crack initiation and crack growth were examined by replica investigation. Calculation result of equivalent stress intensity factor shows crack growth under equi-biaxial stress is faster than under uniaxial stress. It is concluded that equi-biaxial fatigue behavior should be considered in the evaluation of fatigue crack initiation and crack growth. (author)

  5. 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.

  6. Mechanism of biaxial pre-stress method on welding residual stress and hot cracks controlling

    Institute of Scientific and Technical Information of China (English)

    LIU Xuesong; ZHOU Guangtao; WANG Ping; LIU Haoyuan; FANG Hongyuan

    2009-01-01

    Based on the conventional uniaxial pre-tensile stress method during welding, this study presents a new method of welding with biaxial pre-stress. With the help of numerical simulation, experiments were carried out on the self-designed device. Except for the control on residual stress and distortion as-welded, the experimental results also show its effect on the prevention of hot cracks, thus this method can make up for the disadvantage of the conventional pre-stress method. Hot cracks

  7. Long-term strength of Kh13M2S2 in biaxial stressed state

    International Nuclear Information System (INIS)

    Long-term strength of thin-walled tubular and plane samples of Kh13M2S2 steel at 650 deg C was studied. The tubular samples were loaded with internal gas pressure which resulted in a biaxial stressed state, the plane ones were loaded with uniaxial extension. Statistical processing of the experimental results was carried out, the straight lines of long-term strength with confidence intervals were plotted. Of four studied criteria of the complex stressed state the best coincidence of the experimental results under biaxial and uniaxial load is obtained using the Lebedev criterion

  8. The failure behavior of the cladding with outer surface pre-crack in biaxial stress test

    International Nuclear Information System (INIS)

    Biaxial stress tests using the unirradiated Cold Worked Stress Relieved (CWSR) Zircaloy-4 cladding with an outer surface pre-crack were conducted under room temperature condition. To reproduce the biaxial stress states assumed in RIA conditions, Expansion Due to Compression (EDC) test which induces uniaxial stress states was developed using a tensile test machine. Constant tensile loads, 0, 5.0 and 10.0 kN, were applied to specimens through each test, respectively. All specimens failed in the tests, and the failure morphology was similar to that observed in the PIEs conducted for the pulse irradiation experiments using a high burnup fuel. The longitudinal strain (εtz) at failure clearly increased with increasing tensile loads and the circumferential strain (εtθ) at failure decreased significantly in 5.0 and 10.0 kN tests compared to 0 kN tests. These data obtained in this study are considered as the fundamentals to quantify the failure criteria of claddings in a biaxial stress state. (author)

  9. On the correct interpretation of measured force and calculation of material stress in biaxial tests.

    Science.gov (United States)

    Nolan, D R; McGarry, J P

    2016-01-01

    Biaxial tests are commonly used to investigate the mechanical behaviour of soft biological tissues and polymers. In the current paper we uncover a fundamental problem associated with the calculation of material stress from measured force in standard biaxial tests. In addition to measured forces, localised unmeasured shear forces also occur at the clamps and the inability to quantify such forces has significant implications for the calculation of material stress from simplified force-equilibrium relationships. Unmeasured shear forces are shown to arise due to two distinct competing contributions: (1) negative shear force due to stretching of the orthogonal clamp, and (2) positive shear force as a result of material Poisson-effect. The clamp shear force is highly dependent on the specimen geometry and the clamp displacement ratio, as consequently, is the measured force-stress relationship. Additionally in this study we demonstrate that commonly accepted formulae for the estimation of material stress in the central region of a cruciform specimen are highly inaccurate. A reliable empirical correction factor for the general case of isotropic materials must be a function of specimen geometry and the biaxial clamp displacement ratio. Finally we demonstrate that a correction factor for the general case of non-linear anisotropic materials is not feasible and we suggest the use of inverse finite element analysis as a practical means of interpreting experimental data for such complex materials. PMID:26327453

  10. Band offsets for biaxially and uniaxially stressed silicon-germanium layers with arbitrary substrate and channel orientations

    Science.gov (United States)

    Eneman, Geert; Roussel, Philippe; Brunco, David Paul; Collaert, Nadine; Mocuta, Anda; Thean, Aaron

    2016-08-01

    The conduction and valence band offsets between a strained silicon-germanium layer and a silicon-germanium substrate are reported for arbitrary substrate and channel crystal orientations. The offsets are calculated both for the case of biaxial stress, corresponding approximately to the stress state of a thin strained channel in a planar field-effect transistor (FET), and for uniaxial stress, which is the approximate stress state for strained channels in a FinFET configuration. Significant orientation dependence is found for the conduction band offset, overall leading to the strongest electron quantum confinement in biaxial-tensile stressed channels on {100}-oriented substrates, and uniaxial-tensile stressed channels in the ⟨100⟩ and ⟨110⟩ directions. For biaxially stressed layers on {111} substrates, the conduction band offset is significantly smaller than for {100} or {110} directions. For the valence band offset, the dependence on crystal orientation is found to be small.

  11. A novel biaxial specimen for inducing residual stresses in thermoset polymers and fibre composite material

    DEFF Research Database (Denmark)

    Jakobsen, Johnny; Andreasen, Jens Henrik; Jensen, Martin

    2015-01-01

    A new type of specimen configuration with the purpose of introducing a well-defined biaxial residual (axisymmetric) stress field in a neat thermoset or a fibre composite material is presented. The ability to experimentally validate residual stress predictions is an increasing need for design...... engineers when they challenge the material limits in present and future thermoset and composite component. In addition to the new specimen configuration, this paper presents an analytical solution for the residual stress state in the specimen. The analytical solution assumes linear elastic and isotropic...... material behaviour. Experimental strain release measurements and the analytical solution determine the residual stress state present in the material. A demonstration on neat epoxy is conducted and residual stress predictions of high accuracy and repeatability have been achieved. The precise determination...

  12. ANALYTICAL SOLUTIONS TO STRESS CONCENTRATION PROBLEM IN PLATES CONTAINING RECTANGULAR HOLE UNDER BIAXIAL TENSIONS

    Institute of Scientific and Technical Information of China (English)

    Yi Yang; Jike Liu; Chengwu Cai

    2008-01-01

    The stress concentration problem in structures with a circular or elliptic hole can be investigated by analytical methods.For the problem with a rectangular hole,only approximate results are derived.This paper deduces the analytical solutions to the stress concentration problem in plates with a rectangular hole under biaxial tensions.By using the U-transformation technique and the finite element method,the analytical displacement solutions of the finite element equations are derived in the series form.Therefore,the stress concentration can then be discussed easily and conveniently.For plate problem the bilinear rectangular element with four nodes is taken as an example to demonstrate the applicability of the proposed method.The stress concentration factors for various ratios of height to width of the hole are obtained.

  13. Biaxial stresses, surface roughness and microstructure in evaporated TiO2 films with different deposition geometries

    International Nuclear Information System (INIS)

    The residual stresses, surface roughness and microstructure in titanium oxide films prepared by electron-beam evaporation and deposited with different geometries were investigated, with particular focus on the in-plane anisotropy of the biaxial stresses and microstructures. Thin films were deposited with various deposition angles on B270 glass substrates and silicon wafers. Two different types of deposition geometries were studied. The residual stress in the thin films was examined by a phase-shifting Twyman-Green interferometer. The optical constants, biaxial stress and surface roughness were found to be related to the evolution of the anisotropic microstructures in the films. The results revealed that the anisotropic stresses that developed in the evaporated titanium oxide films were dependent upon the deposition geometry and microstructure of the films.

  14. Behavior of dam concrete under biaxial compression-tension and triaxial compression-compression-tension stresses

    Institute of Scientific and Technical Information of China (English)

    Huailiang WANG; Yupu SONG

    2008-01-01

    In order to meet the requirement for nonlinear analysis and design of mass concrete structures, the deformation behavior and strength of three-graded con-crete specimens 250 mm × 250 mm × 400 mm with a maximum aggregate size of 80 mm and the corresponding wet-screened concrete specimens 150 mm × 150 mm × 300 mm with a maximum aggregate size of 40 mm were studied experimentally. Specimens subjected to biaxial com-pression-tension (C-T) and triaxial compression-compres-sion-tension (C-C-T) stress states. Test data indicate that both the deformation and strength of the mass concrete specimens are lower than those of the corresponding wet-screened concrete small specimens, but the initial tangent modulus of the stress-strain curve of the former is greater than that of the latter. Test results show that the wet-screened effect and size effect of the specimens under com-plex stress states are obvious such that these should be con-sidered in the design of mass concrete structures. In addition, respective failure criteria for mass concrete in prin-cipal stress space and octahedron stress space are proposed.

  15. Numerical and experimental analysis of the directional stability on crack propagation under biaxial stresses

    Energy Technology Data Exchange (ETDEWEB)

    RodrIguez-MartInez, R; Urriolagoitia-Calderon, G; Urriolagoitia-Sosa, G; Hernandez-Gomez, L H [Instituto Politecnico Nacional Seccion de Estudios de Posgrado e Investigacion (SEPI), Escuela Superior de IngenierIa Mecanica y Electrica (ESIME), Edificio 5. 2do Piso, Unidad Profesional Adolfo Lopez Mateos ' Zacatenco' Col. Lindavista, C.P. 07738, Mexico, D.F. (Mexico); Merchan-Cruz, E A; RodrIguez-Canizo, R G; Sandoval-Pineda, J M, E-mail: rrodriguezm@ipn.m, E-mail: urrio332@hotmail.co, E-mail: guiurri@hotmail.co, E-mail: luishector56@hotmail.co, E-mail: eamerchan@gmail.co, E-mail: ricname@hotmail.co, E-mail: jsandovalp@ipn.m [Instituto Politecnico Nacional Seccion de Estudios de Posgrado e Investigacion (SEPI), Escuela Superior de IngenierIa Mecanica y Electrica (ESIME). Unidad profesional, AZCAPOTZALCO, Av. de las Granjas No. 682, Col. Sta. Catarina Azcapotzalco, C.P. 02550, Mexico D.F. (Mexico)

    2009-08-01

    In this paper, the case of Single Edge Notch (SEN) specimens subject to opening/compressive loading was analyzed; The loads are applied in several ratios to evaluate the influence of the specimen geometry, and the Stress Intensity Factor (SIF) K{sub 1} values on the directional stability of crack propagation. The main purpose of this work is to evaluate the behaviour of the fracture propagation, when modifying the geometry of the SEN specimen and different relationships of load tension/compression are applied. Additionally, the precision of the numerical and experimental analysis is evaluated to determine its reliability when solving this type of problems. The specimens are subjected to biaxial opening/compression loading; both results (numerical and experimental) are compared in order to evaluate the condition of directional stability on crack propagation. Finally, an apparent transition point related to the length of specimens was identified, in which the behaviour of values of SIF changes for different loading ratios.

  16. Application of magnetomechanical hysteresis modeling to magnetic techniques for monitoring neutron embrittlement and biaxial stress

    International Nuclear Information System (INIS)

    The objective is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. Interaction between experiment and modeling should suggest efficient magnetic measurement procedures for determining neutron embrittlement biaxial stress. This should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. In the first six months of this first year study, magnetic measurements were made on steel surveillance specimens from the Indian Point 2 and D.C. Cook 2 reactors. The specimens previously had been characterized by Charpy tests after specified neutron fluences. Measurements now included: (1) hysteresis loop measurement of coercive force, permeability and remanence, (2) Barkhausen noise amplitude; and (3) higher order nonlinear harmonic analysis of a 1 Hz magnetic excitation. Very good correlation of magnetic parameters with fluence and embrittlement was found for specimens from the Indian Point 2 reactor. The D.C. Cook 2 specimens, however showed poor correlation. Possible contributing factors to this are: (1) metallurgical differences between D.C. Cook 2 and Indian Point 2 specimens; (2) statistical variations in embrittlement parameters for individual samples away from the stated men values; and (3) conversion of the D.C. Cook 2 reactor to a low leakage core configuration in the middle of the period of surveillance. Modeling using a magnetomechanical hysteresis model has begun. The modeling will first focus on why Barkhausen noise and nonlinear harmonic amplitudes appear to be better indicators of embrittlement than the hysteresis loop parameters

  17. Photoluminescence spectra and biaxial stress effects of yellow 1S excitons in Cu{sub 2}O thin films recrystallized epitaxially between paired MgO plates

    Energy Technology Data Exchange (ETDEWEB)

    Aihara, S., E-mail: shingoauniv@gmail.com [Graduate School of Science and Technology, Kumamoto University, 2-39-1, Kurokami Chuo-ku, Kumamoto 860-8555 (Japan); Ota, A. [Graduate School of Science and Technology, Kumamoto University, 2-39-1, Kurokami Chuo-ku, Kumamoto 860-8555 (Japan); Iwamitsu, K. [Graduate School of Science and Technology, Kumamoto University, 2-39-1, Kurokami Chuo-ku, Kumamoto 860-8555 (Japan); Faculty of Science, Kumamoto University, 2-39-1, Kurokami Chuo-ku, Kumamoto 860-8555 (Japan); Ichikawa, F.; Isobe, H. [Graduate School of Science and Technology, Kumamoto University, 2-39-1, Kurokami Chuo-ku, Kumamoto 860-8555 (Japan); Shimamoto, T.; Akai, I. [Institute of Pulsed Power Science, Kumamoto University, 2-39-1, Kurokami Chuo-ku, Kumamoto 860-8555 (Japan)

    2015-11-15

    We investigated biaxial stress effects on the yellow 1S ortho excitons in Cu{sub 2}O thin films recrystallized between paired MgO plates by measuring photoluminescence spectra, X-ray diffraction and polarization microscope images. On the MgO (001) surface, we found two kinds of epitaxial growth modes of the Cu{sub 2}O thin films. In such thin films, the yellow 1S ortho exciton states split into two or three levels depending on the respective epitaxial growth modes due to the different biaxial stresses owing to the lattice mismatches between Cu{sub 2}O and MgO. By using effective Hamiltonians including such biaxial stress effects, we estimated the strengths of the biaxial stresses from the energy splittings of the 1S ortho excitons and confirmed the two kinds of epitaxial growth modes in our Cu{sub 2}O thin films. - Highlights: • Two different oriented Cu{sub 2}O thin films were epitaxially grown between paired MgO (001) plates. • The thin films were applied biaxial stresses due to lattice mismatch between Cu{sub 2}O and MgO. • The lattice mismatch stresses can change yellow 1S exciton states in Cu{sub 2}O thin films. • We report the biaxial stress strengths by analyzing splitting energies of the 1S ortho excitons.

  18. Biaxial stress evaluation in GeSn film epitaxially grown on Ge substrate by oil-immersion Raman spectroscopy

    Science.gov (United States)

    Takeuchi, Kazuma; Suda, Kohei; Yokogawa, Ryo; Usuda, Koji; Sawamoto, Naomi; Ogura, Atsushi

    2016-09-01

    GeSn is being paid much attention as a next-generation channel material. In this work, we performed the excitation of forbidden transverse optical (TO) phonons from strained GeSn, as well as longitudinal optical (LO) phonons, under the backscattering geometry from the (001) surface by oil-immersion Raman spectroscopy. Using the obtained LO/TO phonons, we derived the phonon deformation potentials (PDPs), which play an important role in the stress evaluation, of the strained Ge1‑ x Sn x for the first time. The results suggest that PDPs are almost constant for the Ge1‑ x Sn x (x < 0.032). Biaxial stress calculated using the derived PDPs reasonably indicated the isotropic states.

  19. Biaxial stress evaluation in GeSn film epitaxially grown on Ge substrate by oil-immersion Raman spectroscopy

    Science.gov (United States)

    Takeuchi, Kazuma; Suda, Kohei; Yokogawa, Ryo; Usuda, Koji; Sawamoto, Naomi; Ogura, Atsushi

    2016-09-01

    GeSn is being paid much attention as a next-generation channel material. In this work, we performed the excitation of forbidden transverse optical (TO) phonons from strained GeSn, as well as longitudinal optical (LO) phonons, under the backscattering geometry from the (001) surface by oil-immersion Raman spectroscopy. Using the obtained LO/TO phonons, we derived the phonon deformation potentials (PDPs), which play an important role in the stress evaluation, of the strained Ge1- x Sn x for the first time. The results suggest that PDPs are almost constant for the Ge1- x Sn x (x < 0.032). Biaxial stress calculated using the derived PDPs reasonably indicated the isotropic states.

  20. Interference of wedge-shaped protrusions on the faces of a Griffith crack in biaxial stress. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Boulet, J.A.M. [Tennessee Univ., Knoxville, TN (United States)

    1992-04-01

    An initial investigation of the influence of protrusion interference on the fracture toughness required to prevent unstable propagation of a Griffith crack in a brittle material is described. The interference is caused by relative shear displacement of the crack faces when subjected to remote biaxial stress with neither principal stress parallel to the crack. It is shown that for room temperature cracks smaller than about one centimeter in silicon carbide, or about one millimeter in silicon nitride, the presence of interference changes the fracture stress. A mathematical model based on linear elasticity solutions and including multiple interference sites at arbitrarily specified positions on the crack is presented. Computations of the change in required fracture toughness and its dependence on wedge geometry (size and vertex angle), applied stresses (orientation and magnitude), and location of the interference site are discussed. Results indicate that a single interference site has only a slight effect on required toughness. However, the influence of interference increases monotonically with the number of interference sites. The two-dimensional model described herein is not accurate when the interference sites are closely spaced.

  1. A numerical analysis of stress intensity factors for cracks emanating from an elliptical hole in a rectangular plate under biaxial loads

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Concerns with stress intensity factors for cracks emanating from an elliptical hole in a rectangular plate under biaxial loads by means of a boundary element method which consists of non-singular displacement discontinuity element presented by Crouch and Starfied[6] and crack-tip displacement discontinuity elements proposed by the author. In the boundary elenent implementation the left or the right crack-tip displacement discontinuity element is placed locally at the corresponding left or right crack tip on top of the constant displacement discontinuity elements that cover the entire crack surface and other boundaries. The present numerical results further illustrate that the present numerical approach is very effective and accurate for calculating stress intensity factors of complex cracks in a finite plate and can reveal the effect of the biaxial load and the cracked body geometry on stress intensity factors.

  2. Development and validation of an experimental procedure for studying the biaxial stress corrosion. Application to the systems: alloy-600/air and 316L/MgCl{sub 2}; Developpement et validation d'une procedure experimentale pour l'etude de la corrosion sous contrainte biaxiale. Application aux couples alliage 600 / air et 316L / MgCl{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Farre, M.Th

    1998-07-15

    One of the main preoccupation for maintaining EdF's nuclear pressurised water reactors is intergranular stress corrosion cracking of steam generator tubing (alloy 600: NC 15Fe). The most affected areas (first row U-bend and roll transition zone) are in biaxial stress state. The crack propagation is often axial and sometimes circumferential. The actual life prediction criterion for these structures depends on the maximal principal stress. The purpose of this study is to determine whether it is safe to use such a criterion in a case of biaxial stress state. A procedure is proposed and experimentally validated for designing specimen in a controlled biaxial stress state when submitted to traction. Quadrants I an IV of the stress space are the only ones explored. The aim is to use these specimens in order to realize stress corrosion tests in primary water with alloy 600. The procedure involves studying the biaxial behavior of the material. This shows the effect of hardening on the shape of the yield stress surface. The hardening of alloy 600 is mainly kinematic. The yield stress surface becomes concave in the hardening stress direction and flat in the opposite direction. The geometry of the specimen stems from parameterized shape optimisation. An elasto-viscoplastic behavior law is identified for alloy 600. Use of the law for calculating the strain state of one specimen is experimentally validated. This entire procedure has been successfully validated with biaxial stress corrosion cracking tests, using 316L and MgCl{sub 2} boiling at 154 deg C. In this case it is difficult to determine a life time criterion. It is shown that the criterion of the maximal principal stress is invalid in case of a biaxial stress state. (author)

  3. Investigation of the biaxial stress of Al-doped ZnO thin films on a flexible substrate with RF magnetron sputtering

    Science.gov (United States)

    Huang, Kuo-Ting; Chen, Hsi-Chao; Cheng, Po-Wei; Chang, Jhe-Ming

    2016-01-01

    Transparent conductive Al-doped ZnO (AZO) thin films were deposited onto poly(ethylene terephthalate) (PET) substrate, using the radio frequency (RF) magnetron sputtering method. The residual stress of flexible electronics was investigated by a double beam shadow moiré interferometer with phase shifting interferometry (PSI). Moreover, the biaxial stress of AZO thin films can be graphically represented by using Mohr’s circle of stress. The residual stress of AZO thin films becomes more compressive with the increase in sputtering power. The maximum residual stress is -1115.74 MPa, and the shearing stress is 490.57 MPa at a sputtering power of 200 W. The trends of residual stress were evidenced by the X-ray diffraction (XRD) patterns and optical properties of AZO thin films. According to the evaluation results of the refractive index and the extinction coefficient, the AZO thin films have better quality when the sputtering power less than 100 W.

  4. Acoustic phonon propagation in ultra-thin Si membranes under biaxial stress field

    International Nuclear Information System (INIS)

    We report on stress induced changes in the dispersion relations of acoustic phonons propagating in 27 nm thick single crystalline Si membranes. The static tensile stress (up to 0.3 GPa) acting on the Si membranes was achieved using an additional strain compensating silicon nitride frame. Dispersion relations of thermally activated hypersonic phonons were measured by means of Brillouin light scattering spectroscopy. The theory of Lamb wave propagation is developed for anisotropic materials subjected to an external static stress field. The dispersion relations were calculated using the elastic continuum approximation and taking into account the acousto-elastic effect. We find an excellent agreement between the theoretical and the experimental dispersion relations. (paper)

  5. A fast real time measurement system to track in and out of plane optical retardation/ birefringence, true stress, and true strain during biaxial stretching of polymer films

    Science.gov (United States)

    Cakmak, M.; Hassan, M.; Unsal, E.; Martins, C.

    2012-12-01

    An instrumented and highly integrated biaxial stretching system was designed and constructed to obtain true stress, true strain, and optical behavior of polymeric films during biaxial stretching. With programmable drive motors, any form of temporally varying biaxial deformation profiles, including linear, exponential, logarithmic as well as cyclic, can be applied to a square-shaped films. This machine allows the investigation of mechano-optical behavior of films under profiles captured in industrial processes. To overcome the edge effects, the samples are painted with a dot pattern that is imaged using a high speed video capture system. This system accurately determines the locations of the each dot matrix in subsequent images acquired and calculates the true strains in both directions. The in-plane optical retardation is determined using spectral birefringence method that uses polarized white light and optical spectrometer in the optical train. This is carried out automatically at less than 10 nm in retardation resolution with the light beam passing through the symmetry center of the sample. Out of plane retardation is measured with an identical optical train tilted 45° to the plane of the film with its light beam going through the same spot on the sample as 0° beam. The true stress and birefringences are calculated with the determined instantaneous thickness of the film. With this system, the stress optical behavior of PET's is determined up to very large deformation levels at moderate to high deformation rates. Beyond the initial linear stress optical behavior, these films exhibit sudden positive deviation from linearity and this start of nonlinearity was directly associated with the stress induced crystallization.

  6. Biaxial fatigue of metals the present understanding

    CERN Document Server

    Schijve, Jaap

    2016-01-01

    Problems of fatigue under multiaxial fatigue loads have been addressed in a very large number of research publications. The present publication is primarily a survey of biaxial fatigue under constant amplitude loading on metal specimens. It starts with the physical understanding of the fatigue phenomenon under biaxial fatigue loads. Various types of proportional and non-proportional biaxial fatigue loads and biaxial stress distributions in a material are specified. Attention is paid to the fatigue limit, crack nucleation, initial micro crack growth and subsequent macro-crack in different modes of crack growth. The interference between the upper and lower surfaces of a fatigue crack is discussed. Possibilities for predictions of biaxial fatigue properties are analysed with reference to the similarity concept. The significance of the present understanding for structural design problems is considered. The book is completed with a summary of major observations.

  7. Ultrasonic fatigue testing device under biaxial bending

    Directory of Open Access Journals (Sweden)

    C. Brugger

    2016-07-01

    Full Text Available A new fatigue testing device has been developed to test specimens under biaxial loading at 20 kHz. A flat smooth specimen with a disc geometry is placed on a torus frame and cyclically loaded at the center of its upper face. Disc bending generates a biaxial proportional stress state at the center of the lower face. Any positive loading ratio can be applied. A cast aluminum alloy (used to produce cylinder heads has been tested under biaxial bending using this device in order to determine its fatigue strength at 109 cycles under high hydrostatic pressure. Self-heating is moderate but macroscopic fatigue cracks after testing are very long. First results in VHCF regime are consistent with literature results obtained under similar stress state but in HCF regime and at 20 Hz.

  8. The effects of biaxial loading on the fracture characteristics of several engineering materials

    Science.gov (United States)

    Jones, D. L.; Poulose, P. K.; Liebowitz, H.

    1986-01-01

    Using the George Washington University biaxial test system, a static fracture toughness study of two polymers (PMMA and PVC) and three aluminum alloys was performed for several variations in specimen geometry. Photoelastic experiments indicate that the applied load biaxiality has a very strong influence on the size and shape of the crack-tip stress field, and fracture toughness values for both polymers were seen to decrease with increasing load biaxiality. The load biaxiality was also found to have a strong influence on the crack growth direction in PMMA and a negligible influence on the PVC. The 7075-T6 aluminum toughness values increased with biaxiality, while intermediate peak toughness values were noted at a 0.5 biaxiality ratio for the more ductile 2024-T3 and 6061-T4 alloys. Fracture toughnesses at the highest biaxiality ratios were found to be equal to the uniaxial results.

  9. Biaxial Creep Specimen Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    JL Bump; RF Luther

    2006-02-09

    This report documents the results of the weld development and abbreviated weld qualification efforts performed by Pacific Northwest National Laboratory (PNNL) for refractory metal and superalloy biaxial creep specimens. Biaxial creep specimens were to be assembled, electron beam welded, laser-seal welded, and pressurized at PNNL for both in-pile (JOYO reactor, O-arai, Japan) and out-of-pile creep testing. The objective of this test campaign was to evaluate the creep behavior of primary cladding and structural alloys under consideration for the Prometheus space reactor. PNNL successfully developed electron beam weld parameters for six of these materials prior to the termination of the Naval Reactors program effort to deliver a space reactor for Project Prometheus. These materials were FS-85, ASTAR-811C, T-111, Alloy 617, Haynes 230, and Nirnonic PE16. Early termination of the NR space program precluded the development of laser welding parameters for post-pressurization seal weldments.

  10. Biaxial Creep Specimen Fabrication

    International Nuclear Information System (INIS)

    This report documents the results of the weld development and abbreviated weld qualification efforts performed by Pacific Northwest National Laboratory (PNNL) for refractory metal and superalloy biaxial creep specimens. Biaxial creep specimens were to be assembled, electron beam welded, laser-seal welded, and pressurized at PNNL for both in-pile (JOYO reactor, O-arai, Japan) and out-of-pile creep testing. The objective of this test campaign was to evaluate the creep behavior of primary cladding and structural alloys under consideration for the Prometheus space reactor. PNNL successfully developed electron beam weld parameters for six of these materials prior to the termination of the Naval Reactors program effort to deliver a space reactor for Project Prometheus. These materials were FS-85, ASTAR-811C, T-111, Alloy 617, Haynes 230, and Nirnonic PE16. Early termination of the NR space program precluded the development of laser welding parameters for post-pressurization seal weldments

  11. TRIP钢单双向应力状态下的材料行为%Investigation on the material behaviors of TRIP steels under uniaxial and biaxial stress state

    Institute of Scientific and Technical Information of China (English)

    林海; 李先超; 马金龙; 李洪洋

    2013-01-01

    TRIP钢中残余奥氏体的马氏体相变是TRIP钢相变增塑的重要基础,与材料的宏观应力应变状态密切相关.为探索这一微观材料行为与宏观变形条件间的对应关系,该文对低碳Si-MnTRIP600钢杯突变形顶部与过渡区的材料行为进行研究.研究结果表明,杯突过程中变形区顶部为等双拉平面应力状态,过渡区为单拉平面应力状态;TRIP钢的马氏体相变对应变条件非常敏感,随变形量的增加,无论变形区顶部还是过渡区的残余奥氏体体积分数,均呈近线性降低趋势,但随应变的增加则呈逐渐饱和趋势;与底部相比,顶部等双拉平面应力状态更利于残余奥氏体的马氏体相变,在近相同应变条件下,等双拉平面应力状态下的残余奥氏体含量明显低于单拉平面应力状态.Si-Mn TRIP600钢在6%应变条件下,等双拉平面应力状态与单拉平面应力状态的残余奥氏体含量相差约7%.%The martensitic transformation of retained austenite in TRIP steels is the fundamental of TRIP steels phase transformation plasticity,which depend on the macroscopic stress and strain condition greatly.To investigate the relationship between microscopic material behaviors and macroscopic deformation conditions,low-carbon Si-Mn TRIP600 steel material behaviors of top and transitional section in cupping test was studied.It is shown that during cupping test,the stress state of the top section of the deformation area is equal biaxial stretching plane stress,meanwhile,the transitional section is uniaxial stretching plane stress.The martensitic transformation in TRIP steels was sensitive to strain condition,the retained austenite volume fraction in both top and transitional section shows a nearly linear decrease trend with the increasing of strain.But the trend of gradual saturation can also be found with the increasing of strain.Compared with the bottom,the equal biaxial stretching plane stress condition in the top

  12. Fragmentation in Biaxial Tension

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, G H; Archbold, G C; Hurricane, O A; Miller, P L

    2006-06-13

    We have carried out an experiment that places a ductile stainless steel in a state of biaxial tension at a high rate of strain. The loading of the ductile metal spherical cap is performed by the detonation of a high explosive layer with a conforming geometry to expand the metal radially outwards. Simulations of the loading and expansion of the metal predict strain rates that compare well with experimental observations. A high percentage of the HE loaded material was recovered through a soft capture process and characterization of the recovered fragments provided high quality data, including uniform strain prior to failure and fragment size. These data were used with a modified fragmentation model to determine a fragmentation energy.

  13. Numerical and experimental study of cruciform specimens subjected to biaxial tensile test

    Science.gov (United States)

    Andrusca, L.; Goanta, V.; Barsanescu, P. D.; Steigmann, R.

    2016-08-01

    Multiaxial stress states are very common in engineering applications. To obtain a plane stress state in a material are used different experimental procedures. Biaxial tensile tests of cruciform specimens represent one of the most versatile techniques with accurate results for a wide range of materials. Specimen geometry and size must be adapted to biaxial experiments that use devices attached to universal testing machine. Biaxial tensile tests are performed using cruciform specimens optimized by a numerical study through finite element analysis and a custom built attachable device developed. The results obtained show that the method proposed in this paper can be used with good results to characterize the behaviour of ductile materials.

  14. Biaxial Testing of 2219-T87 Aluminum Alloy Using Cruciform Specimens

    Science.gov (United States)

    Dawicke, D. S.; Pollock, W. D.

    1997-01-01

    A cruciform biaxial test specimen was designed and seven biaxial tensile tests were conducted on 2219-T87 aluminum alloy. An elastic-plastic finite element analysis was used to simulate each tests and predict the yield stresses. The elastic-plastic finite analysis accurately simulated the measured load-strain behavior for each test. The yield stresses predicted by the finite element analyses indicated that the yield behavior of the 2219-T87 aluminum alloy agrees with the von Mises yield criterion.

  15. Biaxial fatigue behavior of a powder metallurgical TRIP steel

    Directory of Open Access Journals (Sweden)

    S. Ackermann

    2015-10-01

    had partially mode II orientation (tilted 45° to the loading axes and afterwards bifurcated into two pairs of mode I cracks. Another shear test revealed a major crack of mode I orientation (parallel to the loading axes. These results are in good agreement to the literature. Micro cracks after shear fatigue were longer than those after biaxial fatigue with strain ratios of 1 and 0.5. Major and minor cracks after equibiaxial and shear loading showed crack branching and crack coalescence. The results on fatigue crack behavior support the assumption that the period of stage I (mode II crack propagation is much longer under shear loading than under other biaxial conditions due to absence of tensile stress normal to the planes of maximum shear strain under shear loading

  16. Singular values, nematic disclinations, and emergent biaxiality

    OpenAIRE

    Dennis, Mark R.; Žumer, Slobodan; Kamien, Randall D.; Čopar, Simon

    2015-01-01

    Both uniaxial and biaxial nematic liquid crystals are defined by orientational ordering of their building blocks. While uniaxial nematics only orient the long molecular axis, biaxial order implies local order along three axes. As the natural degree of biaxiality and the associated frame that can be extracted from the tensorial description of the nematic order vanishes in the uniaxial phase, we extend the nematic director to a full biaxial frame by making use of a singular value decomposition ...

  17. Design and Use of a Novel Bioreactor for Regeneration of Biaxially Stretched Tissue-Engineered Vessels.

    Science.gov (United States)

    Huang, Angela Hai; Lee, Yong-Ung; Calle, Elizabeth A; Boyle, Michael; Starcher, Barry C; Humphrey, Jay D; Niklason, Laura E

    2015-08-01

    Conventional bioreactors are used to enhance extracellular matrix (ECM) production and mechanical strength of tissue-engineered vessels (TEVs) by applying circumferential strain, which is uniaxial stretching. However, the resulting TEVs still suffer from inadequate mechanical properties, where rupture strengths and compliance values are still very different from native arteries. The biomechanical milieu of native arteries consists of both circumferential and axial loading. Therefore, to better simulate the physiological stresses acting on native arteries, we built a novel bioreactor system to enable biaxial stretching of engineered arteries during culture. This new bioreactor system allows for independent control of circumferential and axial stretching parameters, such as displacement and beat rate. The assembly and setup processes for this biaxial bioreactor system are reliable with a success rate greater than 75% for completion of long-term sterile culture. This bioreactor also supports side-by-side assessments of TEVs that are cultured under three types of mechanical conditions (static, uniaxial, and biaxial), all within the same biochemical environment. Using this bioreactor, we examined the impact of biaxial stretching on arterial wall remodeling of TEVs. Biaxial TEVs developed the greatest wall thickness compared with static and uniaxial TEVs. Unlike uniaxial loading, biaxial loading led to undulated collagen fibers that are commonly found in native arteries. More importantly, the biaxial TEVs developed the most mature elastin in the ECM, both qualitatively and quantitatively. The presence of mature extracellular elastin along with the undulated collagen fibers may contribute to the observed vascular compliance in the biaxial TEVs. The current work shows that biaxial stretching is a novel and promising means to improve TEV generation. Furthermore, this novel system allows us to optimize biomechanical conditioning by unraveling the interrelationships among the

  18. Flexural rigidity of biaxially loaded reinforced concrete rectangular column sections

    Science.gov (United States)

    Resheidat, M.; Ghanma, M.; Sutton, C.; Chen, Wai-Fah

    1995-05-01

    An exact analysis is carried out utilizing the parabola-rectangle stress-strain curve for concrete and a typical idealized stress-strain curve for steel to develop the moment-curvature relationship for biaxially loaded reinforced concrete rectangular column sections. Based on that, the flexural rigidity EI of the section is determined at the yield curvature. A computer program is written by FORTRAN 77 to handle the required computations. The influence of material properties, the effect of steel ratios, and the impact of axial loads on the EI estimation were investigated. This study leads to the development of a new equation to estimate the flexural rigidity EI of reinforced concrete biaxially loaded rectangular columns in which these factors were considered. It is shown that the new equation stems from the actual behavior of the column. Therefore, it is recommended for general use in the design of slender columns.

  19. Development of pressurized disc type fatigue testing system for equi-biaxial fatigue

    International Nuclear Information System (INIS)

    A testing method for investigating fatigue strength under equi-biaxial stress/strain condition was developed. In this method, the equi-biaxial stress condition was achieved by applying pressure on the surfaces of a disc-type specimen, for which the disc edge was constrained by supporting jigs. Air pressure was used to apply the cyclic loading and the failure of the specimen was determined by detecting the crack penetration of the specimen thickness. This method allows application of the cyclic equi-biaxial stress without a complex testing apparatus or a complex controlling system such as the testing system using the cruciform or tubular specimens, conventionally used for the fatigue test under the equi-biaxial stress condition. After developing the testing system, the configuration of the disc-type specimen was designed by finite element analysis so that a crack would be initiated at the center of the specimen. Then, carbon steel (SS400 in JIS) specimens were subjected to the fatigue test. The developed system was demonstrated to be able to initiate a fatigue crack at the center of the specimen and to detect the specimen failure successfully. The test results showed that the fatigue lifetime under equi-biaxial stress was longer than that under uniaxial stress for the same Von Mises equivalent strain range. (author)

  20. Biaxially oriented film on flexible polymeric substrate

    Science.gov (United States)

    Finkikoglu, Alp T.; Matias, Vladimir

    2009-10-13

    A flexible polymer-based template having a biaxially oriented film grown on the surface of a polymeric substrate. The template having the biaxially oriented film can be used for further epitaxial growth of films of interest for applications such as photovoltaic cells, light emitting diodes, and the like. Methods of forming such a flexible template and providing the polymeric substrate with a biaxially oriented film deposited thereon are also described.

  1. Fatigue of Clip connectors for offshore drilling risers under biaxial tension

    Directory of Open Access Journals (Sweden)

    Gaur Vidit

    2014-06-01

    Full Text Available Drilling riser connectors designed by IFPEN undergo cyclic in-phase biaxial tension in their critical area. This type of loading was reproduced on steel tubular specimens loaded in cyclic tension and internal pressure. The fatigue lives were substantially reduced when the load biaxiality was increased from 0 to 0.4 and then further to 1, which was not captured by existing fatigue criteria. A deeper investigation is thus in progress. Emphasis is laid on the separate evaluation of mean stress and biaxiality effects, often treated in the same way in existing criteria. The influence of load biaxiality on the resistance of the steel to fatigue-corrosion in seawater will also be investigated.

  2. Biaxial wheel/hub test facility. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, G.; Grubisic, V. [eds.

    2000-07-01

    The 4{sup th} meeting aims to exchange the experience and knowledge of engineers during several presentations and discussions about new developments required for a reliable, time and cost reducing validation of the wheel/hub assembly. Tremendous development of the wheel performance, described by the ratio of the rated load (kg) versus the wheel weight (kg) had taken place during the last 5000 years. Starting from the ratio of 3 for wooden 2-piece-disc-wheels in Mesopotamia it needed nearly 1000 years to increase the ratio to approx 5 at light-weight spoke wheels for fighting carriages, found in the grave of king Tutenchamon in Egypt. Modern light alloy wheels of commercial vehicles reach values up to 160 kg/kg. Additionally the comlex design of the modern systems for cars and commercial vehicles comprising wheel, brake, hub, bearing, spindle and hub carrier, including different materials and their treatment, fasteners, press-fits, require an appropriate testing procedure. The variable loading conditions, caused by operational wheel forces, brake and torque moments including heating, may result in changing tolerances and press-fits during operation and consequently in different damage mechanisms. This can be simulated in the Biaxial Wheel Test Machine, whereby corresponding load programs are necessary. An overview about all biaxial test machines in usage at the end of 1999 is shown in the introduction. The total number is 17 for cars, 7 for commercial vehicles and 1 for trains. The six presentations of this meeting were consequently concentrated on: (a) recommendations for a standardization of load programs of the German Wheel Committee, (b) the simulation of brake and torque events and (c) the possibility for a numerical stress analyses and fatigue life assessment. (orig./AKF)

  3. Discrete Element Simulations and Experiments on the Deformation of Cohesive Powders in a bi-axial Box

    OpenAIRE

    Imole, O.I.; Kumar, N; Magnanimo, V.; S. Luding

    2012-01-01

    We compare element test experiments and simulations on the deformation of frictional, cohesive particles in a bi-axial box. We show that computer simulations with the Discrete Element Method qualitatively reproduce a uniaxial compression element test in the true bi-axial tester. We highlight the effects of friction and polydispersity on our simulations and present the second stress response namely the deviatoric stress as a function of the deviatoric strain.

  4. An experimental study on the biaxial strength of the plain concrete for containment structures

    International Nuclear Information System (INIS)

    In this paper, an experimental study into the biaxial strength of plain concrete for containment structures is represented and technical difficulties encountered in the development of a suitable test setup are discussed. Prior to testing for a 1/8 model of cylindrical specimen(φ150x300) and four 1/4 models of plate specimens(200x200xT(=30, 50, 60, 70)mm) under uniaxial compression, the strength ratios between both specimens with different geometry shapes were found by nonlinear finite element analyses using ABAQUS. From the results three suitable type of considered plate specimens were selected for failure testing under biaxial stress. As initial approach to develop biaxial strength criteria of plain concrete, the various test data were obtained under uniaxial compression, uniaxial tension and biaxial compression. The test data indicate that the strength of concrete under biaxial compression, f1=f2, is 14.7 percent larger than under uniaxial compression and the Poisson's ratio of concrete is 0.155. Teflon employed to eliminate friction between test specimen and loading platens showed and excellent effect under biaxial compression, f1=f2

  5. Biaxial loading effects on fracture toughness of reactor pressure vessel steel

    International Nuclear Information System (INIS)

    The preliminary phases of a program to develop and evaluate fracture methodologies for assessing crack-tip constraint effects on fracture toughness of reactor pressure vessel (RPV) steels have been completed by the Heavy-Section Steel Technology (HSST) Program. Objectives were to investigate effect of biaxial loading on fracture toughness, quantify this effect through existing stress-based, dual-parameter, fracture-toughness correlations, or propose and verify alternate correlations. A cruciform beam specimen with 2-D, shallow, through-thickness flaw and a special loading fixture was designed and fabricated. Tests were performed using biaxial loading ratios of 0:1 (uniaxial), 0.6:1, and 1:1 (equi-biaxial). Critical fracture-toughness values were calculated for each test. Biaxial loading of 0.6:1 resulted in a reduction in the lower bound fracture toughness of ∼12% as compared to that from the uniaxial tests. The biaxial loading of 1:1 yielded two subsets of toughness values; one agreed well with the uniaxial data, while one was reduced by ∼43% when compared to the uniaxial data. Results were evaluated using J-Q theory and Dodds-Anderson (D-A) micromechanical scaling model. The D-A model predicted no biaxial effect, while the J-Q method gave inconclusive results. When applied to the 1:1 biaxial data, these constraint methodologies failed to predict the observed reduction in fracture toughness obtained in one experiment. A strain-based constraint methodology that considers the relationship between applied biaxial load, the plastic zone width in the crack plane, and fracture toughness was formulated and applied successfully to the data. Evaluation of this dual-parameter strain-based model led to the conclusion that it has the capability of representing fracture behavior of RPV steels in the transition region, including the effects of out-of-plane loading on fracture toughness. This report is designated as HSST Report No. 150

  6. Fracture assessment of HSST Plate 14 shallow-flaw cruciform bend specimens tested under biaxial loading conditions

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-06-01

    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 the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states.

  7. Fracture assessment of HSST Plate 14 shallow-flaw cruciform bend specimens tested under biaxial loading conditions

    International Nuclear Information System (INIS)

    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 the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states

  8. Evaluation of constraint methodologies applied to a shallow-flaw cruciform bend specimen tested under biaxial loading conditions

    International Nuclear Information System (INIS)

    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 prototypic, 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 RPV materials. 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

  9. Engineering piezoresistivity using biaxially strained silicon

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Richter, Jacob; Brandbyge, Mads;

    2008-01-01

    We calculate the shear piezocoefficient of p-type silicon with grown-in biaxial strain using a 66 k·p method. We find a significant increase in the value of the shear piezocoefficient for compressive grown-in biaxial strain, while tensile strain decreases the piezocoefficient. The dependence...... of the piezocoefficient on temperature and dopant density is altered qualitatively for strained silicon. In particular, we find that a vanishing temperature coefficient may result for silicon with grown-in biaxial tensile strain. These results suggest that strained silicon may be used to engineer the iezoresistivity...

  10. Biaxial ferromagnetic liquid crystal colloids.

    Science.gov (United States)

    Liu, Qingkun; Ackerman, Paul J; Lubensky, Tom C; Smalyukh, Ivan I

    2016-09-20

    The design and practical realization of composite materials that combine fluidity and different forms of ordering at the mesoscopic scale are among the grand fundamental science challenges. These composites also hold a great potential for technological applications, ranging from information displays to metamaterials. Here we introduce a fluid with coexisting polar and biaxial ordering of organic molecular and magnetic colloidal building blocks exhibiting the lowest symmetry orientational order. Guided by interactions at different length scales, rod-like organic molecules of this fluid spontaneously orient along a direction dubbed "director," whereas magnetic colloidal nanoplates order with their dipole moments parallel to each other but pointing at an angle to the director, yielding macroscopic magnetization at no external fields. Facile magnetic switching of such fluids is consistent with predictions of a model based on competing actions of elastic and magnetic torques, enabling previously inaccessible control of light. PMID:27601668

  11. Graphene flakes under controlled biaxial deformation

    Science.gov (United States)

    Androulidakis, Charalampos; Koukaras, Emmanuel N.; Parthenios, John; Kalosakas, George; Papagelis, Konstantinos; Galiotis, Costas

    2015-12-01

    Thin membranes, such as monolayer graphene of monoatomic thickness, are bound to exhibit lateral buckling under uniaxial tensile loading that impairs its mechanical behaviour. In this work, we have developed an experimental device to subject 2D materials to controlled equibiaxial strain on supported beams that can be flexed up or down to subject the material to either compression or tension, respectively. Using strain gauges in tandem with Raman spectroscopy measurements, we monitor the G and 2D phonon properties of graphene under biaxial strain and thus extract important information about the uptake of stress under these conditions. The experimental shift over strain for the G and 2D Raman peaks were found to be in the range of 62.3 ± 5 cm-1/%, and 148.2 ± 6 cm-1/%, respectively, for monolayer but also bilayer graphenes. The corresponding Grüneisen parameters for the G and 2D peaks were found to be between 1.97 ± 0.15 and 2.86 ± 0.12, respectively. These values agree reasonably well with those obtained from small-strain bubble-type experiments. The results presented are also backed up by classical and ab initio molecular dynamics simulations and excellent agreement of Γ-E2g shifts with strains and the Grüneisen parameter was observed.

  12. A confocal rheoscope to study bulk or thin-film material under uniaxial or biaxial shear

    CERN Document Server

    Lin, Neil Y C; Cheng, Xiang; Leahy, Brian; Cohen, Itai

    2016-01-01

    We present a new design of a confocal rheoscope that enables us to precisely impose a uniform uniaxial or biaxial shear. The design consists of two precisely-positioned parallel plates. Our design allows us to adjust the gap between the plates to be as small as 2$\\pm$0.1 $\\mu$m, allowing for the exploration of confinement effects. By using our shear cell in conjunction with a biaxial force measurement device and a high-speed confocal microscope, we are able to measure the real-time biaxial stress while simultaneously imaging the material 3D structure. We illustrate the importance of the instrument capabilities by discussing the applications of this instrument in current and future research topics in colloidal suspensions.

  13. STRAIN-CONTROLLED BIAXIAL TENSION OF NATURAL RUBBER: NEW EXPERIMENTAL DATA

    KAUST Repository

    Pancheri, Francesco Q.

    2014-03-01

    We present a new experimental method and provide data showing the response of 40A natural rubber in uniaxial, pure shear, and biaxial tension. Real-time biaxial strain control allows for independent and automatic variation of the velocity of extension and retraction of each actuator to maintain the preselected deformation rate within the gage area of the specimen. Wealso focus on the Valanis-Landel hypothesis that is used to verify and validate the consistency of the data.Weuse a threeterm Ogden model to derive stress-stretch relations to validate the experimental data. The material model parameters are determined using the primary loading path in uniaxial and equibiaxial tension. Excellent agreement is found when the model is used to predict the response in biaxial tension for different maximum in-plane stretches. The application of the Valanis-Landel hypothesis also results in excellent agreement with the theoretical prediction.

  14. Vertically aligned biaxially textured molybdenum thin films

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, Rahul [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Riley, Michael [Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Lee, Sabrina [US Army Armament Research, Development and Engineering Center, Benet Labs, Watervliet, New York 12189 (United States); Lu, Toh-Ming [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2011-09-15

    Vertically aligned, biaxially textured molybdenum nanorods were deposited using dc magnetron sputtering with glancing flux incidence (alpha = 85 degrees with respect to the substrate normal) and a two-step substrate-rotation mode. These nanorods were identified with a body-centered cubic crystal structure. The formation of a vertically aligned biaxial texture with a [110] out-of-plane orientation was combined with a [-110] in-plane orientation. The kinetics of the growth process was found to be highly sensitive to an optimum rest time of 35 seconds for the two-step substrate rotation mode. At all other rest times, the nanorods possessed two separate biaxial textures each tilted toward one flux direction. While the in-plane texture for the vertical nanorods maintains maximum flux capture area, inclined Mo nanorods deposited at alpha = 85 degrees without substrate rotation display a [-1-1-4] in-plane texture that does not comply with the maximum flux capture area argument. Finally, an in situ capping film was deposited with normal flux incidence over the biaxially textured vertical nanorods resulting in a thin film over the porous nanorods. This capping film possessed the same biaxial texture as the nanorods and could serve as an effective substrate for the epitaxial growth of other functional materials.

  15. Biaxial tensile tests of the porcine ascending aorta.

    Science.gov (United States)

    Deplano, Valérie; Boufi, Mourad; Boiron, Olivier; Guivier-Curien, Carine; Alimi, Yves; Bertrand, Eric

    2016-07-01

    One of the aims of this work is to develop an original custom built biaxial set-up to assess mechanical behavior of soft tissues. Stretch controlled biaxial tensile tests are performed and stereoscopic digital image correlation (SDIC) is implemented to measure the 3D components of the generated displacements. Using this experimental device, the main goal is to investigate the mechanical behavior of porcine ascending aorta in the more general context of human ascending aorta pathologies. The results highlight that (i) SDIC arrangement allows accurate assessment of displacements and so stress strain curves, (ii) porcine ascending aorta has a nearly linear and anisotropic mechanical behavior until 30% of strain, (iii) porcine ascending aorta is stiffer in the circumferential direction than in the longitudinal one, (iv) the material coefficient representing the interaction between the two loading directions is thickness dependent, (v) taking into account the variability of the samples the stress values are independent of the stretch rate in the range of values from 10(-3) to 10(-1)s(-1) and finally, (vi) unlike other segments of the aorta, 4-month-old pigs ascending aorta is definitely not a relevant model to investigate the mechanical behavior of the human ascending aorta. PMID:27211783

  16. Growth of inclined fatigue cracks using the biaxial CJP model

    Directory of Open Access Journals (Sweden)

    G. Laboviciute

    2015-07-01

    Full Text Available The CJP model of crack tip stresses is a modified version of the Williams crack tip stress field which takes account of simplified stress distributions that arise from the presence of a zone of plastic deformation associated with the crack flanks and crack tip, and that act on the elastic field responsible for driving crack growth. The elastic stress field responsible for crack growth is therefore controlled by the applied loading and by the induced boundary stresses at the interface with the plastic zone. This meso-scale model of crack tip stresses leads to a modified set of crack tip stress intensity factors that include the resultant influence of plastic wake-induced crack tip shielding, and which therefore have the potential to help resolve some longstanding controversies associated with plasticity-induced closure. A full-field approach has now been developed for stress using photoelasticity and also for displacement using digital image correlation. This paper considers the characterisation of crack growth rate data with the biaxial CJP model, using compact tension specimens that contain inclined cracks at the notch tip with initial angles of 30°, 45° and 60° to the horizontal axis. Significant experimental difficulties are experienced in growing cracks in a biaxial field under uniaxial tensile loading, as the natural tendency of the crack is to turn so that it becomes perpendicular to the maximum principal stress direction. However, crack angle is not an issue in the CJP model which calculates the stress field parallel with, and perpendicular to, the crack plane. These stress components can be rotated into directions comparable with the usual KI and KII directions and used to calculate stress intensity parameters that should be directly comparable with the standard stress intensity formulations. Another difficulty arises, however, in finding published expressions for KI and KII for CT specimens with curved or kinked cracks. The CJP model

  17. Biaxial tension on polymer in thermoforming range

    Directory of Open Access Journals (Sweden)

    Billon N.

    2010-06-01

    Full Text Available This paper presents an experimental characterization of mechanical properties of a polyethylene terephtalate (PET resin classically used in stretch blow moulding process. We have applied on such a material a well established experimental protocol at CEMEF, including new and relevant biaxial tensile tests. The experimental set-up relative to biaxial tension will be presented and described in a first part of the paper. Furthermore, we will focus on the experimental DMTA preliminary tests which are required to estimate the resin sensibility to temperature and strain rate in linear viscoelasticity domain. Finally, we will be interested in the material large strain behaviour: biaxial tensile results are presented and discussed. Finally, such an experimental approach should allow a relevant modelling of polymer physics and mechanics; this point will not be discussed here because of a lack of time.

  18. Biaxial tension on polymer in thermoforming range

    Science.gov (United States)

    Becker, S.; Combeaud, C.; Fournier, F.; Rodriguez, J.; Billon, N.

    2010-06-01

    This paper presents an experimental characterization of mechanical properties of a polyethylene terephtalate (PET) resin classically used in stretch blow moulding process. We have applied on such a material a well established experimental protocol at CEMEF, including new and relevant biaxial tensile tests. The experimental set-up relative to biaxial tension will be presented and described in a first part of the paper. Furthermore, we will focus on the experimental DMTA preliminary tests which are required to estimate the resin sensibility to temperature and strain rate in linear viscoelasticity domain. Finally, we will be interested in the material large strain behaviour: biaxial tensile results are presented and discussed. Finally, such an experimental approach should allow a relevant modelling of polymer physics and mechanics; this point will not be discussed here because of a lack of time.

  19. Topology Optimization of Stressed Capacitive RF MEMS Switches

    DEFF Research Database (Denmark)

    Philippine, Mandy A.; Sigmund, Ole; Rebeiz, Gabriel M.;

    2013-01-01

    Geometry design can improve a capacitive radio-frequency microelectromechanical system switch's reliability by reducing the impacts of intrinsic biaxial stresses and stress gradients on the switch's membrane. Intrinsic biaxial stresses cause stress stiffening, whereas stress gradients cause out-o...

  20. Towards the biaxial nematic phase via specific intermolecular interactions

    CERN Document Server

    Omnes, L

    2001-01-01

    The work described in this thesis has been focussed on the search of an elusive liquid crystal phase, known as the biaxial nematic phase. Indeed, despite nearly thirty years of intense research, no-one has been able to characterise unambiguously a biaxial nematic phase in a low-molar-mass thermotropic system. Our research is based on the concept of molecular biaxiality as distinct from shape biaxiality. Thus, we are seeking to design palladium complexes where specific intermolecular interactions could exist. Therefore, a few original synthetic strategies were developed to tackle the challenge of discovering the biaxial nematic phase

  1. Dynamic biaxial tissue properties of the human cadaver aorta.

    Science.gov (United States)

    Shah, Chirag S; Hardy, Warren N; Mason, Matthew J; Yang, King H; Van Ee, Chris A; Morgan, Richard; Digges, Kennerly

    2006-11-01

    This study focuses on the biaxial mechanical properties of planar aorta tissue at strain rates likely to be experienced during automotive crashes. It also examines the structural response of the whole aorta to longitudinal tension. Twenty-six tissue-level tests were conducted using twelve thoracic aortas harvested from human cadavers. Cruciate samples were excised from the ascending, peri-isthmic, and descending regions. The samples were subjected to equibiaxial stretch at two nominal speed levels using a new biaxial tissue-testing device. Inertia-compensated loads were measured to facilitate calculation of true stress. High-speed videography and regional correlation analysis were used to track ink dots marked on the center of each sample to obtain strain. In a series of component-level tests, the response of the intact thoracic aorta to longitudinal stretch was obtained using seven aorta specimens. The aorta fails within the peri-isthmic region. The aorta fails in the transverse direction, and the intima fails before the media or adventitia. The aorta tissue exhibits nonlinear behavior. The aorta as complete structure can transect completely from 92 N axial load and 0.221 axial strain. Complete transection can be accompanied by intimal tears. These results have application to finite element modeling and the better understanding of traumatic rupture of the aorta. PMID:17311166

  2. Structural stability and theoretical strength of Cu crystal under equal biaxial loading

    Indian Academy of Sciences (India)

    Jian-Min Zhang; Zhong-Liang Lin; Yan Zhang; Vincent Ji

    2010-02-01

    Cu has been used extensively to replace Al as interconnects in ULSI and MEMS devices. However, because of the difference in the thermal expansion coefficients between the Cu film and the Si substrate, large biaxial stresses will be generated in the Cu film. Thus, the Cu film becomes unstable and even changes its morphologies which affects the device manufacturing yield and ultimate reliability. The structural stability and theoretical strength of Cu crystal under equal biaxial loading have been investigated by combining the MAEAM with Milstein-modified Born stability criteria. The results indicate that, under sufficient tension, there exists a stress-free BCC phase which is unstable and slips spontaneously to a stress-free metastable BCT phase by consuming internal energy. The stable region ranges from −15.131 GPa to 2.803 GPa in the theoretical strength or from −5.801% to 4.972% in the strain respectively.

  3. Biaxial load effects on the crack border elastic strain energy and strain energy rate

    Science.gov (United States)

    Eftis, J.; Subramonian, N.; Liebowitz, H.

    1977-01-01

    The validity of the singular solution (first term of a series representation) is investigated for the crack tip stress and displacement field in an infinite sheet with a flat line crack with biaxial loads applied to the outer boundaries. It is shown that if one retains the second contribution to the series approximations for stress and displacement in the calculation of the local elastic strain energy density and elastic strain energy rate in the crack border region, both these quantities have significant biaxial load dependency. The value of the J-integral does not depend on the presence of the second term of the series expansion for stress and displacement. Thus J(I) is insensitive to the presence of loads applied parallel to the plane of the crack.

  4. Failure Investigation for QP Steel Sheets under uniaxial and Equal-Biaxial Tension Conditions

    Science.gov (United States)

    Zou, Danqing; Li, Shuhui; He, Ji; Cui, Ronggao

    2016-08-01

    The Quenching and Partitioning (QP) steel sheet is new generation material to induce phase transformation for plasticity in forming vehicle parts. The phase transformation is strongly stress state dependent behavior in experiments, which should affect the failure timing and limit strain in forming processes. In this paper, Nakajima test with QP980 and DP1000 steel sheets under equal-biaxial loading condition is performed for failure behavior. X-ray diffraction (XRD) is adopted to obtain the volume fraction of retained austenite (fA). Digital Image Correlation (DIC) is used to record the surface strain field and its evolution during equal-biaxial tension deformation. The same level Dual Phase (DP) steel is also employed for the purpose of comparison. The results show that phase transformation in QP steel gives small impact on failure strain under equal biaxial tension condition which is contradicted with our understanding. It suggests that failure behavior under uniaxial tension of QP980 is strongly phase transformation dependent. But it shows almost independent under equal biaxial tension condition.

  5. 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.

  6. Biaxial testing for fabrics and foils optimizing devices and procedures

    CERN Document Server

    Beccarelli, Paolo

    2015-01-01

    This book offers a well-structured, critical review of current design practice for tensioned membrane structures, including a detailed analysis of the experimental data required and critical issues relating to the lack of a set of design codes and testing procedures. The technical requirements for biaxial testing equipment are analyzed in detail, and aspects that need to be considered when developing biaxial testing procedures are emphasized. The analysis is supported by the results of a round-robin exercise comparing biaxial testing machines that involved four of the main research laboratories in the field. The biaxial testing devices and procedures presently used in Europe are extensively discussed, and information is provided on the design and implementation of a biaxial testing rig for architectural fabrics at Politecnico di Milano, which represents a benchmark in the field. The significance of the most recent developments in biaxial testing is also explored.

  7. Behavior of High Water-cement Ratio Concrete under Biaxial Compression after Freeze-thaw Cycles

    Institute of Scientific and Technical Information of China (English)

    SHANG Huaishuai; SONG Yupu; OU Jinping

    2008-01-01

    The high water-cement ratio concrete specimens under biaxial compression that completed in a triaxial testing machine were experimentally studied.Strength and deformations of plain concrete specimens after 0,25,50 cycles of freeze-thaw.Influences of freeze-thaw cycles and stress ratio on the peak stress and deformation of this point were analyzed aecording to the experimental results.Based on the test data,the failure criterion expressed in terms of principal stress after difierent cycles of freeze-thaw,and the failure criterion with consideration of the influence of freeze-thaw cycle and sffess ratio were proposed respectively.

  8. Time-dependent biaxial mechanical behavior of the aortic heart valve leaflet.

    Science.gov (United States)

    Stella, John A; Liao, Jun; Sacks, Michael S

    2007-01-01

    Despite continued progress in the treatment of aortic valve (AV) disease, current treatments continue to be challenged to consistently restore AV function for extended durations. Improved approaches for AV repair and replacement rests upon our ability to more fully comprehend and simulate AV function. While the elastic behavior the AV leaflet (AVL) has been previously investigated, time-dependent behaviors under physiological biaxial loading states have yet to be quantified. In the current study, we performed strain rate, creep, and stress-relaxation experiments using porcine AVL under planar biaxial stretch and loaded to physiological levels (60 N/m equi-biaxial tension), with strain rates ranging from quasi-static to physiologic. The resulting stress-strain responses were found to be independent of strain rate, as was the observed low level of hysteresis ( approximately 17%). Stress relaxation and creep results indicated that while the AVL exhibited significant stress relaxation, it exhibited negligible creep over the 3h test duration. These results are all in accordance with our previous findings for the mitral valve anterior leaflet (MVAL) [Grashow, J.S., Sacks, M.S., Liao, J., Yoganathan, A.P., 2006a. Planar biaxial creep and stress relaxatin of the mitral valve anterior leaflet. Annals of Biomedical Engineering 34 (10), 1509-1518; Grashow, J.S., Yoganathan, A.P., Sacks, M.S., 2006b. Biaxial stress-stretch behavior of the mitral valve anterior leaflet at physiologic strain rates. Annals of Biomedical Engineering 34 (2), 315-325], and support our observations that valvular tissues are functionally anisotropic, quasi-elastic biological materials. These results appear to be unique to valvular tissues, and indicate an ability to withstand loading without time-dependent effects under physiologic loading conditions. Based on a recent study that suggested valvular collagen fibrils are not intrinsically viscoelastic [Liao, J., Yang, L., Grashow, J., Sacks, M.S., 2007

  9. Biaxial thermal creep of Inconel 617 and Haynes 230 at 850 and 950 °C

    International Nuclear Information System (INIS)

    The biaxial thermal creep behavior of Inconel 617 and Haynes 230 at 850 and 950 °C was investigated. Biaxial stresses were generated using the pressurized tube technique. The detailed creep deformation and fracture mechanism have been studied. Creep curves for both alloys showed that tertiary creep accounts for a greater portion of the materials’ life, while secondary creep only accounts for a small portion. Fractographic examinations of the two alloys indicated that nucleation, growth, and coalescence of creep voids are the dominant micro-mechanisms for creep fracture. At 850 °C, alloy 230 has better creep resistance than alloy 617. When subjected to the biaxial stress state, the creep rupture life of the two alloys was considerably reduced when compared to the results obtained by uniaxial tensile creep tests. The Monkman–Grant relation proves to be a promising method for estimating the long-term creep life for alloy 617, whereas alloy 230 does not follow the relation. This might be associated with the significant changes in the microstructure of alloy 230 at high temperatures

  10. Biaxial thermal creep of Inconel 617 and Haynes 230 at 850 and 950 °C

    Energy Technology Data Exchange (ETDEWEB)

    Tung, Hsiao-Ming, E-mail: hmtung2@gmail.com [Institute of Nuclear Energy Research, Longtan, Taoyuan 32546, Taiwan, ROC (China); Mo, Kun; Stubbins, James F. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States)

    2014-04-01

    The biaxial thermal creep behavior of Inconel 617 and Haynes 230 at 850 and 950 °C was investigated. Biaxial stresses were generated using the pressurized tube technique. The detailed creep deformation and fracture mechanism have been studied. Creep curves for both alloys showed that tertiary creep accounts for a greater portion of the materials’ life, while secondary creep only accounts for a small portion. Fractographic examinations of the two alloys indicated that nucleation, growth, and coalescence of creep voids are the dominant micro-mechanisms for creep fracture. At 850 °C, alloy 230 has better creep resistance than alloy 617. When subjected to the biaxial stress state, the creep rupture life of the two alloys was considerably reduced when compared to the results obtained by uniaxial tensile creep tests. The Monkman–Grant relation proves to be a promising method for estimating the long-term creep life for alloy 617, whereas alloy 230 does not follow the relation. This might be associated with the significant changes in the microstructure of alloy 230 at high temperatures.

  11. Biaxial thermal creep of Inconel 617 and Haynes 230 at 850 and 950 °C

    Science.gov (United States)

    Tung, Hsiao-Ming; Mo, Kun; Stubbins, James F.

    2014-04-01

    The biaxial thermal creep behavior of Inconel 617 and Haynes 230 at 850 and 950 °C was investigated. Biaxial stresses were generated using the pressurized tube technique. The detailed creep deformation and fracture mechanism have been studied. Creep curves for both alloys showed that tertiary creep accounts for a greater portion of the materials' life, while secondary creep only accounts for a small portion. Fractographic examinations of the two alloys indicated that nucleation, growth, and coalescence of creep voids are the dominant micro-mechanisms for creep fracture. At 850 °C, alloy 230 has better creep resistance than alloy 617. When subjected to the biaxial stress state, the creep rupture life of the two alloys was considerably reduced when compared to the results obtained by uniaxial tensile creep tests. The Monkman-Grant relation proves to be a promising method for estimating the long-term creep life for alloy 617, whereas alloy 230 does not follow the relation. This might be associated with the significant changes in the microstructure of alloy 230 at high temperatures.

  12. Characterization Of Biaxial Strain Of Poly(L-Lactide) Tubes

    DEFF Research Database (Denmark)

    Løvdal, Alexandra Liv Vest; Andreasen, Jens Wenzel; Mikkelsen, Lars Pilgaard;

    2016-01-01

    . Through further WAXS analysis it was found that the SEQ biaxial strain yields larger interplanar spacing and distorted crystals and looser packing of chains. However, this does not influence the mechanical properties negatively. A loss of orientation in SEQ biaxial strained samples at high degrees...

  13. Biaxially textured articles formed by power metallurgy

    Science.gov (United States)

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-26

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100} orientation texture; and further having a Curie temperature less than that of pure Ni.

  14. Biaxially textured articles formed by powder metallurgy

    Science.gov (United States)

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-07-29

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100} orientation texture; and further having a Curie temperature less than that of pure Ni.

  15. Biaxially textured articles formed by powder metallurgy

    Science.gov (United States)

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2004-09-14

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100} orientation texture; and further having a Curie temperature less than that of pure Ni.

  16. Biaxial crystal-based optical tweezers

    DEFF Research Database (Denmark)

    Angelsky, Oleg V.; Maksimyak, Andrew P.; Maksimyak, Peter P.;

    2010-01-01

    We suggest an optical tweezer setup based on an optically biaxial crystal. To control movements of opaque particles, we use shifts. The results of experimental studies are reported which are concerned with this laser tweezer setup. We demonstrate a movement of microparticles of toner using a sing...... a singular-optical trap, rotation of particles due to orbital angular momentum of the field, and converging or diverging of two different traps when changing transmission plane of polariser at the input of our polarisation interferometer....

  17. Magnetic response of FeNbCuBSi RQ ribbons to bi-axial strain

    International Nuclear Information System (INIS)

    Nanocrystalline strip samples of the FeNbCuBSi class that are macroscopically heterogeneous due to surface /volume differences have been investigated. This heterogeneity is found to be a general property of the class. It represents a base for mutual force influence between the surface and the majority volume beneath. The bi-axial in-plane stress exerted by the ribbon surfaces on the volume is demonstrated first of all by a magnetoelastic anisotropy. The contribution of the creep-induced anisotropy, which can build up under the surface stress at post-treatment temperature, is also found possible

  18. Tensile Property of Bi-axial Warp Knitted Structure

    Institute of Scientific and Technical Information of China (English)

    沈为

    2003-01-01

    The tensile property of bi-axial warp knitted fabrics is tested and compared with that of the plain weave fabric. The results show that there are obvious differences between the tensile property of a bi-axial warp knitted fabric and that of a plain weave fabric.The former can give fuller play to the property of a high modulus yarn than the latter. The tensile strength of a bi-axial warp knitted fabric is linear with the number of yarns in the direction of force.

  19. Conductive and robust nitride buffer layers on biaxially textured substrates

    Science.gov (United States)

    Sankar, Sambasivan [Chicago, IL; Goyal, Amit [Knoxville, TN; Barnett, Scott A [Evanston, IL; Kim, Ilwon [Skokie, IL; Kroeger, Donald M [Knoxville, TN

    2009-03-31

    The present invention relates to epitaxial, electrically conducting and mechanically robust, cubic nitride buffer layers deposited epitaxially on biaxially textured substrates such as metals and alloys. The invention comprises of a biaxially textured substrate with epitaxial layers of nitrides. The invention also discloses a method to form such epitaxial layers using a high rate deposition method as well as without the use of forming gases. The invention further comprises epitaxial layers of oxides on the biaxially textured nitride layer. In some embodiments the article further comprises electromagnetic devices which may have superconducting properties.

  20. Mechanical Properties of Reactive Powder Concrete under Biaxial Compression%双轴压下活性粉末混凝土的力学性能

    Institute of Scientific and Technical Information of China (English)

    余自若; 安明喆; 王志建

    2011-01-01

    为了满足对活性粉末混凝土(RPC)结构进行非线性分析和设计的需要,通过试验研究了RPC试件在双轴受压状态下的强度和变形特性,分析了RPC的破坏形态、双轴抗压极限强度、峰值应变、应力-应变曲线等变化规律,给出了RPC的二轴峰值应力包络图与峰值应变包络图,建立了主应力空间下RPC的双轴破坏准则,为RPC按多轴强度理论进行设计提供了试验依据.%For purpose of performing the nonlinear analysis and designing reactive powder concrete(RPC) structure, experimental investigation of the deformation and strength of RPC specimens with size of 150 mmX 150 mmX50 mm under biaxial compression was carried out. The stresses and strains at the biaxial loading directions of RPC specimens were obtained under biaxial strain controlled loading condition. Based on the test data, the change rule of the failure modes, biaxial comprehensive stress, peak strain and the stress-strain curves were studied. The biaxial strength envelop and peak strain envelops of RPC were obtained. The formula of Kupfer-Gerstle failure criterion for RPC under biaxial compression is proposed, which provide experimental base for the design of RPC structure considering the multi-axial strength.

  1. Biaxial Behavior of Ultra-High Performance Concrete and Untreated UHPC Waffle Slab Bridge Deck Design and Testing

    OpenAIRE

    D'Alessandro, Kacie Caple

    2013-01-01

    Ultra-high performance concrete (UHPC) was evaluated as a potential material for future bridge deck designs. Material characterization tests took place to identify potential challenges in mixing, placing, and curing UHPC. Biaxial testing was performed to evaluate behavior of UHPC in combined tension and compression stress states. A UHPC bridge deck was designed to perform similarly to a conventional concrete bridge deck, and a single unit bridge deck section was tested to evaluate the desi...

  2. Shear Piezoelectricity in Poly(vinylidenefluoride-co-trifluoroethylene): Full Piezotensor Coefficients by Molecular Modeling, Biaxial Transverse Response, and Use in Suspended Energy-Harvesting Nanostructures.

    Science.gov (United States)

    Persano, Luana; Catellani, Alessandra; Dagdeviren, Canan; Ma, Yinji; Guo, Xiaogang; Huang, Yonggang; Calzolari, Arrigo; Pisignano, Dario

    2016-09-01

    The intrinsic flexible character of polymeric materials causes remarkable strain deformations along directions perpendicular to the applied stress. The biaxial response in the shear piezoelectricity of polyvinylidenefluoride copolymers is analyzed and their full piezoelectric tensors are provided. The microscopic shear is exploited in single suspended nanowires bent by localized loading to couple flexural deformation and transverse piezoelectric response.

  3. Three-Dimensional Static and Dynamic Analysis of a Composite Cruciform Structure Subjected to Biaxial Loading: A Discontinuum Approach

    Science.gov (United States)

    Navarro-Zafra, J.; Curiel-Sosa, J. L.; Serna Moreno, M. C.

    2016-04-01

    A three-dimensional structural integrity analysis using the eXtended Finite Element Method (XFEM) is considered for simulating the crack behaviour of a chopped fibre-glass-reinforced polyester (CGRP) cruciform specimen subjected to a quasi-static tensile biaxial loading. This is the first time this problem is accomplished for computing the stress intensity factors (SIFs) produced in the biaxially loaded area of the cruciform specimen. A static crack analysis for the calculation of the mixed-mode SIFs is carried out. SIFs are calculated for infinite plates under biaxial loading as well as for the CGRP cruciform specimens in order to review the possible edge effects. A ratio relating the side of the central zone of the cruciform and the crack length is proposed. Additionally, the initiation and evolution of a three-dimensional crack are successfully simulated. Specific challenges such as the 3D crack initiation, based on a principal stress criterion, and its front propagation, in perpendicular to the principal stress direction, are conveniently addressed. No initial crack location is pre-defined and an unique crack is developed. Finally, computational outputs are compared with theoretical and experimental results validating the analysis.

  4. Measurement and material modeling of biaxial work-hardening behavior for pure titanium sheet

    Science.gov (United States)

    Sumita, Takeshi; Kuwabara, Toshihiko

    2013-12-01

    Biaxial tensile tests of a commercial pure titanium sheet (JIS ♯1) were performed using a servo-controlled multiaxial tube expansion testing machine developed by one of the authors [Kuwabara, T. and Sugawara, F., Multiaxial tube expansion test method for measurement of sheet metal deformation behavior under biaxial tension for a large strain range, Int. J. Plasticity, 45 (2013), 103-118]. Tubular specimens with an inner diameter of 54 mm were fabricated by roller bending and TIG welding the as-received test material with a thickness of 0.5 mm. Several linear stress paths in the first quadrant of the stress space were applied to the tubular specimens to measure the contours of plastic work and the directions of the plastic strain rates for an equivalent plastic strain range of 0.05 ≤ ɛ0p ≤ 0.30. It was found that the shapes of the work contours significantly changed with an increase in ɛ0p and that the Yld2000-2d yield function could reproduce the differential work hardening behavior of the test material by changing the material parameters and the exponent as functions of ɛ0p.

  5. Determination of flow curves under equibiaxial stress conditions

    NARCIS (Netherlands)

    Mulder, J.; Vegter, H.; Ha, J.J.; Boogaard, van den A.H.

    2012-01-01

    Three experimental methods have been used to establish flow curves for a low carbon steel under biaxial stress conditions: the hydraulic bulge test, the stack compression test and the biaxial tensile test. The individual tests are discussed and the results for a DC06 IF steel grade compared. Initial

  6. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry

    Science.gov (United States)

    Aho, Johnathon M.; Qiang, Bo; Wigle, Dennis A.; Tschumperlin, Daniel J.; Urban, Matthew W.

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal-submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa-submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered esophageal

  7. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry

    Science.gov (United States)

    Aho, Johnathon M.; Qiang, Bo; Wigle, Dennis A.; Tschumperlin, Daniel J.; Urban, Matthew W.

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal–submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa–submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered

  8. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry.

    Science.gov (United States)

    Aho, Johnathon M; Qiang, Bo; Wigle, Dennis A; Tschumperlin, Daniel J; Urban, Matthew W

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal-submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa-submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered esophageal

  9. Method for forming biaxially textured articles by powder metallurgy

    Science.gov (United States)

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2002-01-01

    A method of preparing a biaxially textured alloy article comprises the steps of preparing a mixture comprising Ni powder and at least one powder selected from the group consisting of Cr, W, V, Mo, Cu, Al, Ce, YSZ, Y, Rare Earths, (RE), MgO, CeO.sub.2, and Y.sub.2 O.sub.3 ; compacting the mixture, followed by heat treating and rapidly recrystallizing to produce a biaxial texture on the article. In some embodiments the alloy article further comprises electromagnetic or electro-optical devices and possesses superconducting properties.

  10. A shear stabilized biaxial texture in a lamellar block copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Polis, D.L.; Pinheiro, B.S.; Winey, K.I.; Lakis, R.E. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    1996-12-31

    Block copolymers spontaneously self-assemble into a variety of morphologies. Recent studies have produced a biaxial texture in poly(styrene-b-ethylene propylene), SEP, diblock copolymers by applying oscillatory shear. This biaxial texture consists of {open_quotes}parallel{close_quotes} lamellae (normal to lamellae aligned perpendicular to shearing surfaces) and {open_quotes}transverse{close_quotes} lamellae (normal to lamellae aligned parallel to shearing direction) according to small-angle X-ray scattering, SAXS. The present study has determined how these two populations of lamellae are arranged and how they relax upon quiescent annealing by examining the superstructure via FE-SEM.

  11. Irreversible magnetic processes under biaxial and uniaxial magnetic anisotropies

    Science.gov (United States)

    Pokharel, S.; Akioya, O.; Alqhtany, N. H.; Dickens, C.; Morgan, W.; Wuttig, M.; Lisfi, A.

    2016-05-01

    Irreversible magnetic processes have been investigated in magnetic systems with two different anisotropy symmetries (uniaxial and biaxial) through angular measurement of the switching field, the irreversible susceptibility and the magnetic viscosity. These two systems consist of two-dimensional cobalt ferrite hetero-structures epitaxially grown on (100) and (110) MgO substrate. It is found that for uniaxial anisotropy the irreversible characteristics of the magnetization are large and display a strong angular dependence, which exhibits its maximum at the easy axis and drops quickly to vanish at the hard axis. However, for biaxial anisotropy the magnetization irreversible characteristics are considerably reduced and are less sensitive to the field angle.

  12. Detection of an intermediate biaxial phase in the phase diagram of biaxial liquid crystals: entropic sampling study.

    Science.gov (United States)

    Kamala Latha, B; Jose, Regina; Murthy, K P N; Sastry, V S S

    2014-05-01

    We investigate the phase sequence of biaxial liquid crystals, based on a general quadratic model Hamiltonian over the relevant parameter space, with a Monte Carlo simulation which constructs equilibrium ensembles of microstates, overcoming possible (free) energy barriers (combining entropic and frontier sampling techniques). The resulting phase diagram qualitatively differs from the universal phase diagram predicted earlier from mean-field theory (MFT), as well as the Monte Carlo simulations with the Metropolis algorithm. The direct isotropic-to-biaxial transition predicted by the MFT is replaced in certain regions of the space by the onset of an additional intermediate biaxial phase of very low order, leading to the sequence N(B)-N(B1)-I. This is due to inherent barriers to fluctuations of the components comprising the total energy, and may explain the difficulties in the experimental realization of these phases.

  13. Detection of an intermediate biaxial phase in the phase diagram of biaxial liquid crystals: Entropic sampling study

    Science.gov (United States)

    Kamala Latha, B.; Jose, Regina; Murthy, K. P. N.; Sastry, V. S. S.

    2014-05-01

    We investigate the phase sequence of biaxial liquid crystals, based on a general quadratic model Hamiltonian over the relevant parameter space, with a Monte Carlo simulation which constructs equilibrium ensembles of microstates, overcoming possible (free) energy barriers (combining entropic and frontier sampling techniques). The resulting phase diagram qualitatively differs from the universal phase diagram predicted earlier from mean-field theory (MFT), as well as the Monte Carlo simulations with the Metropolis algorithm. The direct isotropic-to-biaxial transition predicted by the MFT is replaced in certain regions of the space by the onset of an additional intermediate biaxial phase of very low order, leading to the sequence NB-NB1-I. This is due to inherent barriers to fluctuations of the components comprising the total energy, and may explain the difficulties in the experimental realization of these phases.

  14. Residual stresses of water-jet peened austenitic stainless steel

    International Nuclear Information System (INIS)

    The specimen material was austenitic stainless steel, SUS316L. The residual stress was induced by water-jet peening. The residual stress was measured using the 311 diffraction with conventional X-rays. The measured residual stress showed the equi-biaxial stress state. To investigate thermal stability of the residual stress, the specimen was aged thermally at 773K in air to 1000h. The residual stress kept the equi-biaxial stress state against the thermal aging. Lattice plane dependency of the residual stress induced by water-jet peening was evaluated using hard synchrotron X-rays. The residual stress measured by the soft lattice plane showed the equi-biaxial stress state, but the residual stress measured by the hard lattice plane did not. In addition, the distributions of the residual stress in the depth direction were measured using a strain scanning method with hard synchrotron X-rays and neutrons. (author)

  15. Time-evolving collagen-like structural fibers in soft tissues: biaxial loading and spherical inflation

    Science.gov (United States)

    Topol, Heiko; Demirkoparan, Hasan; Pence, Thomas J.; Wineman, Alan

    2016-05-01

    This work considers a previously developed constitutive theory for the time dependent mechanical response of fibrous soft tissue resulting from the time dependent remodeling of a collagen fiber network that is embedded in a ground substance matrix. The matrix is taken to be an incompressible nonlinear elastic solid. The remodeling process consists of the continual dissolution of existing fibers and the creation of new fibers. Motivated by experimental reports on the enzyme degradation of collagen fibers, the remodeling is governed by first order chemical kinetics such that the dissolution rate is dependent upon the fiber stretch. The resulting time dependent mechanical response is sensitive to the natural configuration of the fibers when they are created, and different assumptions on the nature of the fiber's stress free state are considered here. The response under biaxial loading, a type of loading that has particular significance for the characterization of biological materials, is studied. The inflation of a spherical membrane is then analyzed in terms of the equal biaxial stretch that occurs in the membrane approximation. Different assumptions on the natural configuration of the fibers, combined with their time dependent dissolution and reforming, are shown to emulate alternative forms of creep and relaxation response. This formal similarity to viscoelastic phenomena occurs even though the underlying mechanisms are fundamentally different from the mechanism of macromolecular reconfiguration that one typically associates with viscoelastic response.

  16. Fatigue life prediction of magnetorheological elastomers subjected to dynamic equi-biaxial cyclic loading

    International Nuclear Information System (INIS)

    Prediction of fatigue life is of great significance in ensuring that dynamically loaded rubber components exhibit safety and reliability in service. In this text, the dynamic equi-biaxial fatigue behaviour of magnetorheological elastomer (MREs) using a bubble inflation method is described. Wöhler (S–N) curves for both isotropic and anisotropic MREs were produced by subjecting the compounds to cycling over a range of stress amplitudes (σa) between 0.75 MPa and 1.4 MPa. Changes in physical properties, including variation in stress–strain relations and complex modulus (E*) during the fatigue process were analysed. It was found that the complex modulus of MRE samples decreased throughout the entire fatigue test and failure took place at a limiting value of approximately 1.228MPa ± 4.38% for isotropic MREs and 1.295 ± 10.33% for anisotropic MREs. It was also determined that a dynamic stored energy criterion can be used as a plausible predictor in determining the fatigue life of MREs. - Highlights: • The first Wöhler curves for MREs subjected to equi-biaxial loading were presented. • Anisotropic MREs exhibited higher fatigue resistance than isotropic MREs. • There is a limiting value of complex modulus (E*) at which fatigue failure will occur. • The dynamic stored energy criterion can be used as a fatigue life predictor

  17. BEGA-a biaxial excitation Generator for automobiles

    DEFF Research Database (Denmark)

    Scridon, S.; Boldea, Ion; Tutelea, L.;

    2005-01-01

    This paper presents the design and test results for a biaxial excitation generator/motor for automobiles (BEGA), which has a three-phase stator and a salient-pole excited heteropolar rotor with multiple flux barriers filled with low-cost permanent magnets (PMs). For this new generator, the low-vo...

  18. DEM Simulation of Biaxial Compression Experiments of Inherently Anisotropic Granular Materials and the Boundary Effects

    Directory of Open Access Journals (Sweden)

    Zhao-Xia Tong

    2013-01-01

    Full Text Available The reliability of discrete element method (DEM numerical simulations is significantly dependent on the particle-scale parameters and boundary conditions. To verify the DEM models, two series of biaxial compression tests on ellipse-shaped steel rods are used. The comparisons on the stress-strain relationship, strength, and deformation pattern of experiments and simulations indicate that the DEM models are able to capture the key macro- and micromechanical behavior of inherently anisotropic granular materials with high fidelity. By using the validated DEM models, the boundary effects on the macrodeformation, strain localization, and nonuniformity of stress distribution inside the specimens are investigated using two rigid boundaries and one flexible boundary. The results demonstrate that the boundary condition plays a significant role on the stress-strain relationship and strength of granular materials with inherent fabric anisotropy if the stresses are calculated by the force applied on the wall. However, the responses of the particle assembly measured inside the specimens are almost the same with little influence from the boundary conditions. The peak friction angle obtained from the compression tests with flexible boundary represents the real friction angle of particle assembly. Due to the weak lateral constraints, the degree of stress nonuniformity under flexible boundary is higher than that under rigid boundary.

  19. Numerical simulations of biaxial experiments on damage and fracture in sheet metal forming

    Science.gov (United States)

    Gerke, Steffen; Schmidt, Marco; Brünig, Michael

    2016-08-01

    The damage and failure process of ductile metals is characterized by different mechanisms acting on the micro-scale as well as on the macro-level. These deterioration processes essentially depend on the material type and on the loading conditions. To describe these phenomena in an appropriate way a phenomenological continuum damage and fracture model has been proposed. To detect the effects of stress-state-dependent damage mechanisms, numerical simulations of tests with new biaxial specimen geometries for sheet metals have been performed. The experimental results including digital image correlation (DIC) show good agreement with the corresponding numerical analysis. The presented approach based on both experiments and numerical simulation provides several new aspects in the simulation of sheet metal forming processes.

  20. The fine structure of the vortex-beams in the biaxial and biaxially-induced birefringent media caused by the conical diffraction

    CERN Document Server

    Fadeyeva, Tatyana; Anischenko, Pavel; Volyar, Alexander

    2011-01-01

    We consider the paraxial propagation of nondiffracting singular beams inside natural biaxial and biaxially-induced birefringent media in vicinity of one of the optical axes in terms of eigenmode vortex-beams, whose angular momentum does not change upon propagation. We have predicted a series of new optical effects in the natural biaxial crystals such as the stable propagation of vector singular beams bearing the coupled optical vortices with fractional topological charges, the conversion of the zero-order Bessel beam with a uniformly distributed linear polarization into the radially-, azimuthally- and spirally-polarized beams and the conversion of the space-variant linear polarization in the combined beam with coupled vortices. We have revealed that the field structure of the vortex-beams in the biaxially-induced crystals resembles that in the natural biaxial crystals and form the vector structure inherent in the conical diffraction. However, the mode beams in this case do not change the propagation direction...

  1. Identification du comportement de composites en fatigue bi-axiale

    OpenAIRE

    Busca, Damien

    2014-01-01

    La connaissance du comportement de composites sous un état de contraintes multi-axial reste un enjeu majeur pour l’optimisation du dimensionnement des structures. La machine de fatigue bi-axiale présente au LGP permet de générer un état de contrainte bi-axial par l’utilisation d’éprouvettes cruciformes. La conception des éprouvettes reste un enjeu majeur pour les chercheurs pour répondre aux problèmes spécifiques liés aux matériaux composites. Un nouveau type d’éprouvette cruciforme en compos...

  2. Analysis of Deformation Mechanisms Associated with Biaxially Oriented Polypropylene Films

    Science.gov (United States)

    Wang, Yong; Hsu, Shaw Ling

    1998-03-01

    Biaxially oriented samples can be prepared either by simultaneous or sequential deformation along two orthogonal directions. Generally speaking the orientation achieved in the plane of the film is independent of the method. In this study, we demonstrate that for sequential deformation, the degree of orientation achieved in the two orthogonal directions is dependent on initial sample morphology and deformation parameters. The achievable orientation is strongly dependent on the degree of crystallinity and initial crystallite dimensions. Samples containing small crystallites can achieve significantly higher orientation in the transverse direction (restretching step). The ultimate morphology is dictated by the temperature at which second drawing occurs. At lower deformation temperature, rotation of stacked crystalline lamellae can be accomplished to form biaxially oriented films. At higher temperatures, the dominant mechanism is unfolding of crystalline chain segments followed by recrystallization into units aligned with the restretching direction. X-ray diffraction, polarized infrared and Raman spectroscopy, and calorimetric techniques were employed to analyze these structural transformations.

  3. Theory of nine elastic constants of biaxial nematics

    Institute of Scientific and Technical Information of China (English)

    Liu Hong

    2008-01-01

    In this paper, a rotational invariant of interaction energy between two biaxial-shaped molecules is assumed and in the mean field approximation, nine elastic constants for simple distortion patterns in biaxial nematica are derived in terms of the thermal averagewhere D(l)mn is the Wigner rotation matrix.In the lowest order terms, the elastic constants depend on coefficients г,г',λ, order parameters Q0=Q0+Q2vj'j''j(r12) and probability function fk'k'' k (r12), where r12 is the distance between two molecules, andλis proportional to temperature. Q0 and Q2 are parameters related to multiple moments of molecules. Comparing these results with those obtained from Landau-de Gennes theory, we have obtained relationships between coefficients, order parameters used in both theories. In the special case of uniaxial nematics, both results are reduced to a degenerate case where K11=K33.

  4. Aspekte der Modellierung des Tragverhaltens von Textilbeton unter biaxialer Beanspruchung

    OpenAIRE

    Beyer, Frank R.; Zastrau, Bernd W.

    2011-01-01

    Zur Bemessung und Simulation von flächigen Textilbetonstrukturen werden Berechnungsmodelle benötigt, die das Materialverhalten unter biaxialer Beanspruchung abbilden können. Für eindimensionale Strukturen existieren einige Modelle, zu deren Weiterentwicklung eine Erweiterung zur Abbildung des biaxialen Materialverhaltens vorgeschlagen wird. In diesem Beitrag werden die notwendigen Erweiterungen und deren Umsetzbarkeit bei der Modellierung diskutiert und bewertet. For design and simulation...

  5. Design of a biaxial mechanical loading bioreactor for tissue engineering.

    Science.gov (United States)

    Bilgen, Bahar; Chu, Danielle; Stefani, Robert; Aaron, Roy K

    2013-04-25

    We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 μm and a resolution of 20 nm, translating to a positional accuracy of less than 3 μm over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0

  6. Identification of material parameters using bi-axial machine

    OpenAIRE

    Flores, Paulo; de Montleau, P.; Mathonet, V.; Moureaux, P. (collab.); Habraken, Anne

    2004-01-01

    Experimental testing equipment is built in order to identify material parameters of complex phenomenological constitutive laws. This equipment consists in a bi-axial test machine able to perform plane strain and simple shear tests separately or simultaneously and a Miyauchi simple shear test device; an optical extensometer is used to identify the strain field. The article focus on the validation of the results of this new equipment by comparing with results obtained by standard machines and/o...

  7. Efficient Driving of Piezoelectric Transducers Using a Biaxial Driving Technique.

    Directory of Open Access Journals (Sweden)

    Samuel Pichardo

    Full Text Available Efficient driving of piezoelectric materials is desirable when operating transducers for biomedical applications such as high intensity focused ultrasound (HIFU or ultrasound imaging. More efficient operation reduces the electric power required to produce the desired bioeffect or contrast. Our preliminary work [Cole et al. Journal of Physics: Condensed Matter. 2014;26(13:135901.] suggested that driving transducers by applying orthogonal electric fields can significantly reduce the coercivity that opposes ferroelectric switching. We present here the experimental validation of this biaxial driving technique using piezoelectric ceramics typically used in HIFU. A set of narrow-band transducers was fabricated with two sets of electrodes placed in an orthogonal configuration (following the propagation and the lateral mode. The geometry of the ceramic was chosen to have a resonance frequency similar for the propagation and the lateral mode. The average (± s.d. resonance frequency of the samples was 465.1 (± 1.5 kHz. Experiments were conducted in which each pair of electrodes was driven independently and measurements of effective acoustic power were obtained using the radiation force method. The efficiency (acoustic/electric power of the biaxial driving method was compared to the results obtained when driving the ceramic using electrodes placed only in the pole direction. Our results indicate that the biaxial method increases efficiency from 50% to 125% relative to the using a single electric field.

  8. Quantification of Coupled Stiffness and Fiber Orientation Remodeling in Hypertensive Rat Right-Ventricular Myocardium Using 3D Ultrasound Speckle Tracking with Biaxial Testing

    Science.gov (United States)

    Park, Dae Woo; Sebastiani, Andrea; Yap, Choon Hwai; Simon, Marc A.; Kim, Kang

    2016-01-01

    Mechanical and structural changes of right ventricular (RV) in response to pulmonary hypertension (PH) are inadequately understood. While current standard biaxial testing provides information on the mechanical behavior of RV tissues using surface markers, it is unable to fully assess structural and mechanical properties across the full tissue thickness. In this study, the mechanical and structural properties of normotensive and pulmonary hypertension right ventricular (PHRV) myocardium through its full thickness were examined using mechanical testing combined with 3D ultrasound speckle tracking (3D-UST). RV pressure overload was induced in Sprague–Dawley rats by pulmonary artery (PA) banding. The second Piola–Kirchhoff stress tensors and Green-Lagrangian strain tensors were computed in the RV myocardium using the biaxial testing combined with 3D-UST. A previously established non-linear curve-fitting algorithm was applied to fit experimental data to a Strain Energy Function (SEF) for computation of myofiber orientation. The fiber orientations obtained by the biaxial testing with 3D-UST compared well with the fiber orientations computed from the histology. In addition, the re-orientation of myofiber in the right ventricular free wall (RVFW) along longitudinal direction (apex-to-outflow-tract direction) was noticeable in response to PH. For normotensive RVFW samples, the average fiber orientation angles obtained by 3D-UST with biaxial test spiraled from 20° at the endo-cardium to -42° at the epi-cardium (Δ = 62°). For PHRV samples, the average fiber orientation angles obtained by 3D-UST with biaxial test had much less spiral across tissue thickness: 3° at endo-cardium to -7° at epi-cardium (Δ = 10°, P<0.005 compared to normotensive). PMID:27780271

  9. Directional Differences in the Biaxial Material Properties of Fascia Lata and the Implications for Fascia Function

    OpenAIRE

    Eng, Carolyn M.; Pancheri, Francesco Q.; Lieberman, Daniel E.; Biewener, Andrew Austin; Dorfmann, Luis

    2014-01-01

    Fascia is a highly organized collagenous tissue that is ubiquitous in the body, but whose function is not well understood. Because fascia has a sheet-like structure attaching to muscles and bones at multiple sites, it is exposed to different states of multi- or biaxial strain. In order to measure how biaxial strain affects fascia material behavior, planar biaxial tests with strain control were performed on longitudinal and transversely oriented samples of goat fascia lata (FL). Cruciform samp...

  10. Modelization of ratcheting in biaxial experiments

    International Nuclear Information System (INIS)

    A new unified viscoplastic constitutive equation has been developed in order to interpret ratcheting experiments on mechanical structures of fast reactors. The model is based essentially on a generalized Armstrong Frederick equation for the kinematic variable; the coefficients of the dynamic recovery term in this equation is a function of both instantaneous and accumulated inelastic strain which is allowed to vary in an appropriate manner in order to reproduce the experimental ratcheting rate. The validity of the model is verified by comparing predictions with experimental results for austenitic stainless steel (17-12 SPH) tubular specimens subjected to cyclic torsional loading under constant tensile stress at 6000C

  11. Biaxial Behavior of Ultra-High Performance Concrete and Untreated UHPC Waffle Slab Bridge Deck Design and Testing

    Science.gov (United States)

    D'Alessandro, Kacie Caple

    Ultra-high performance concrete (UHPC) was evaluated as a potential material for future bridge deck designs. Material characterization tests took place to identify potential challenges in mixing, placing, and curing UHPC. Biaxial testing was performed to evaluate behavior of UHPC in combined tension and compression stress states. A UHPC bridge deck was designed to perform similarly to a conventional concrete bridge deck, and a single unit bridge deck section was tested to evaluate the design methods used for untreated UHPC. Material tests identified challenges with placing UHPC. A specified compressive strength was determined for structural design using untreated UHPC, which was identified as a cost-effective alternative to steam treated UHPC. UHPC was tested in biaxial tension-compression stress states. A biaxial test method was developed for UHPC to directly apply tension and compression. The influence of both curing method and fiber orientation were evaluated. The failure envelope developed for untreated UHPC with random fiber orientation was suggested as a conservative estimate for future analysis of UHPC. Digital image correlation was also evaluated as a means to estimate surface strains of UHPC, and recommendations are provided to improve consistency in future tests using DIC methods. A preliminary bridge deck design was completed for untreated UHPC and using established material models. Prestressing steel was used as primary reinforcement in the transverse direction. Preliminary testing was used to evaluate three different placement scenarios, and results showed that fiber settling was a potential placement problem resulting in reduced tensile strength. The UHPC bridge deck was redesigned to incorporate preliminary test results, and two single unit bridge deck sections were tested to evaluate the incorporated design methods for both upside down and right-side up placement techniques. Test results showed that the applied design methods would be conservative

  12. Deformation and strain hardening behavior of powder metallurgical TRIP steel under quasi-static biaxial-planar loading

    Energy Technology Data Exchange (ETDEWEB)

    Kulawinski, D., E-mail: dirk.kulawinski@iwt.tu-freiberg.de [Institute of Materials Engineering, Technische Universität Bergakademie Freiberg, Gustav-Zeuner-Street 5, 09599 Freiberg (Germany); Ackermann, S. [Institute of Materials Engineering, Technische Universität Bergakademie Freiberg, Gustav-Zeuner-Street 5, 09599 Freiberg (Germany); Seupel, A. [Institute of Mechanics and Fluid Dynamics, Technische Universität Bergakademie Freiberg, Lampadiusstraße 4, 09599 Freiberg (Germany); Lippmann, T.; Henkel, S. [Institute of Materials Engineering, Technische Universität Bergakademie Freiberg, Gustav-Zeuner-Street 5, 09599 Freiberg (Germany); Kuna, M. [Institute of Mechanics and Fluid Dynamics, Technische Universität Bergakademie Freiberg, Lampadiusstraße 4, 09599 Freiberg (Germany); Weidner, A.; Biermann, H. [Institute of Materials Engineering, Technische Universität Bergakademie Freiberg, Gustav-Zeuner-Street 5, 09599 Freiberg (Germany)

    2015-08-26

    The present paper investigates a metastable austenitic stainless steel under different biaxial-planar load paths by using a cruciform specimen geometry. The material behavior was described by stress–strain curves and initial yield surface. Furthermore, the hardening behavior was determined by load sequence tests. To investigate the influence of the stress state on the martensite formation a ferrite sensor as well as electron backscatter diffraction measurements were used. Two cruciform specimen geometries were utilized and compared for the considered load cases. The stress state within the cruciform specimens was evaluated by an elastic unloading procedure with subsequent calculation of the stress components. Isotropic initial yielding and non-isotropic hardening were found. A recommendation for the use of the cruciform specimen geometry with respect to the load case is given.

  13. Fatigue Behavior of Plain Concrete Under Biaxial Compression:Experiments and Theoretical Model

    Institute of Scientific and Technical Information of China (English)

    朱劲松; 宋玉普; 曹伟

    2003-01-01

    The effects of different lateral confinement stress on the fatigue behavior of and cumulative damage to plain concrete are investigated experimentally. Eighty 100 mm×100 mm×100 mm specimens of ordinary strength concrete are tested under constant- or variable-amplitude fatigue loading and lateral confinement pressure in two orthogonal directions. A fatigue equation is developed by modifying the classical Aas-Jakobsen S-N equation for taking into account the effect of the confined stress on fatigue strength of plain concrete. The results of variable-amplitude fatigue tests indicate that the linear damage theory proposed by Palmgren and Miner is unreasonable in the biaxial stress state. A nonlinear cumulative damage model that could model the effects of the magnitude and sequence of variable-amplitude fatigue loading and lateral confinement pressure is proposed on the basis of the evolution laws of the residual strains in the longitudinal direction during fatigue tests. The residual fatigue life predicted by this model is found to be in good agreement with the results of the experimental research.

  14. Temperature-induced sign reversal of biaxiality observed by conoscopy in some ferroelectric Sm- C* liquid crystals

    OpenAIRE

    Fukuda, Atsuo; VIJ, JAGDISH KUMAR

    2007-01-01

    PUBLISHED Article number 011709 We have studied various ferroelectric liquid crystals to find the average molecular direction of the shortest axis in the perfectly unwound state by using tilted conoscopic measurements. We find that there exist two types of temperature dependencies of the biaxiality. Some materials exhibit increasing biaxiality while others show decreasing biaxiality with increasing temperature. The former shows a temperature-induced sign reversal of biaxiality. Three di...

  15. Experimental realization of biaxial liquid crystal phases in colloidal dispersions of boardlike particles

    NARCIS (Netherlands)

    van den Pol, E; Petukhov, A.V.; Thies-Weesie, D.M.E.; Belov, D.V.; Vroege, G.J.

    2009-01-01

    Biaxial nematic and biaxial smectic phases were found in a colloidal model system of goethite ( -FeOOH) particles with a simple boardlike shape and short-range repulsive interaction. The macroscopic domains were oriented by a magnetic field and their structure was revealed by small angle x-ray scatt

  16. Lattice Spin Simulations of Topological Defects in Biaxial Nematic Films with Homeotropic Surface Alignment

    Science.gov (United States)

    Preeti, Gouripeddi Sai; Zannoni, Claudio; Chiccoli, Cesare; Pasini, Paolo; Sastry, Vanka S. S.

    2013-05-01

    We present a detailed Monte Carlo study of the effects of biaxiality on the textures of nematic films with specific homeotropic boundary conditions. We have used the Straley generalized Hamiltonian for a wide range of biaxial parameters and the differences obtained in the polarized microscopy images are analyzed for the various cases.

  17. Phase Matching of SHG in Arbitrary Directions of Biaxial Crystals

    Institute of Scientific and Technical Information of China (English)

    YANG Shengli; CHEN Mouzhi

    2002-01-01

    In this paper, propagation and polarization characteristics of optical waves in arbitrary directions in a biaxial crystal are analyzed, and universal relationships of refractive index dependence on their propagation directions and the principal refractive indices for two perpendicular polarization waves propagating in arbitrarily directions are derived from indicatrix equation. By using these relationships, methods of collinear phase matching (PM) of SHG are developed, and general expressions of the collinear PM angle dependent of the principal indices are given for SHG in arbitrarily directions. The expressions may be used to make optimization design of PM by computer for the SHG and to select optimum PM direction and to raise the SHG conversion efficiencies.

  18. Material Identification Using a Bi-Axial Test Machine

    OpenAIRE

    Flores, Paulo; Moureaux, Pierre; Habraken, Anne

    2005-01-01

    This paper shows the identification of material parameters for a DC06 IF steel sheet of 0.8 mm by mechanical tests. The experimental equipment used consists of a tensile test machine, a bi-axial test machine able to perform plane-strain and simple shear tests separately or simultaneously and an optical strain gauge. Tensile, plane-strain and simple shear tests were performed at 0°, 45° and 90° from the sheet rolling direction in order to identify Hill 1948 and Hosford 1979 yield criteria. ...

  19. Hole doped Dirac states in silicene by biaxial tensile strain

    KAUST Repository

    Kaloni, Thaneshwor P.

    2013-03-11

    The effects of biaxial tensile strain on the structure, electronic states, and mechanical properties of silicene are studied by ab-initio calculations. Our results show that up to 5% strain the Dirac cone remains essentially at the Fermi level, while higher strain induces hole doped Dirac states because of weakened Si–Si bonds. We demonstrate that the silicene lattice is stable up to 17% strain. It is noted that the buckling first decreases with the strain (up to 10%) and then increases again, which is accompanied by a band gap variation. We also calculate the Grüneisen parameter and demonstrate a strain dependence similar to that of graphene.

  20. FAILURE MODE AND CONSTITUTIVE MODEL OF PLAIN HIGH-STRENGTH HIGH-PERFORMANCE CONCRETE UNDER BIAXIAL COMPRESSION AFTER EXPOSURE TO HIGH TEMPERATURES

    Institute of Scientific and Technical Information of China (English)

    Zhenjun He; Yupu Song

    2008-01-01

    An orthotropic constitutive relationship with temperature parameters for plain highstrength high-performance concrete (HSHPC) under biaxial compression is developed. It is based on the experiments performed for characterizing the strength and deformation behavior at two strength levels of HSHPC at 7 different stress ratios including α = σ2 : σ3 = 0.00 : -1, -0.20 : -1, -0.30 : -1, -0.40 : -1, -0.50 : -1, -0.75 : -1, -1.00 : -1, after the exposure to normal and high temperatures of 20, 200, 300, 400, 500 and 600℃, and using a large static-dynamic true triaxial machine. The biaxial tests were performed on 100 mm × 100 mm × 100 mm cubic specimens, and friction-reducing pads were used consisting of three layers of plastic membrane with glycerine in-between for the compressive loading plane. Based on the experimental results, failure modes of HSHPC specimens were described. The principal static compressive strengths, strains at the peak stress and stress-strain curves were measured; and the influence of the temperature and stress ratios on them was also analyzed. The experimental results showed that the uniaxial compressive strength of plain HSHPC after exposure to high temperatures does not decrease dramatically with the increase of temperature. The ratio of the biaxial to its uniaxial compressive strength depends on the stress ratios and brittleness-stiffness of HSHPC after exposure to different temperature levels. Comparison of the stress-strain results obtained from the theoretical model and the experimental data indicates good agreement.

  1. Implementation of a Biaxial Resonant Fatigue Test Method on a Large Wind Turbine Blade

    Energy Technology Data Exchange (ETDEWEB)

    Snowberg, D.; Dana, S.; Hughes, S.; Berling, P.

    2014-09-01

    A biaxial resonant test method was utilized to simultaneously fatigue test a wind turbine blade in the flap and edge (lead-lag) direction. Biaxial resonant blade fatigue testing is an accelerated life test method utilizing oscillating masses on the blade; each mass is independently oscillated at the respective flap and edge blade resonant frequency. The flap and edge resonant frequency were not controlled, nor were they constant for this demonstrated test method. This biaxial resonant test method presented surmountable challenges in test setup simulation, control and data processing. Biaxial resonant testing has the potential to complete test projects faster than single-axis testing. The load modulation during a biaxial resonant test may necessitate periodic load application above targets or higher applied test cycles.

  2. Resonant biaxial 7-mm MEMS mirror for omnidirectional scanning

    Science.gov (United States)

    Hofmann, U.; Aikio, M.; Janes, J.; Senger, F.; Stenchly, V.; Weiss, M.; Quenzer, H.-J.; Wagner, B.; Benecke, W.

    2013-03-01

    Low-cost automotive laser scanners for environment perception are needed to enable the integration of advanced driver assistant systems (ADAS) into all automotive vehicle segments, a key to reducing the number of traffic accidents on roads. An omnidirectional 360 degree laser scanning concept has been developed based on combination of an omnidirectional lens and a biaxial large aperture MEMS mirror. This omnidirectional scanning concept is the core of a small sized low-cost time-of-flight based range sensor development. This paper describes concept, design, fabrication and first measurement results of a resonant biaxial 7mm gimbal-less MEMS mirror that is electrostatically actuated by stacked vertical comb drives. Identical frequencies of the two resonant axes are necessary to enable the required circle scanning capability. A tripod suspension was chosen since it allows minimizing the frequency splitting of the two resonant axes. Low mirror curvature is achieved by a thickness of the mirror of more than 500 μm. Hermetic wafer level vacuum packaging of such large mirrors based on multiple wafer bonding has been developed to enable to achieve a large mechanical tilt angle of +/- 6.5 degrees in each axis. The 7mm-MEMS mirror demonstrates large angle circular scanning at 1.5kHz.

  3. An experimental study of biaxial yield in modified 9Cr-1Mo steel at room temperature

    Science.gov (United States)

    Ellis, J. R.

    1985-01-01

    Described are two biaxial experiments which investigated yield, hardening, and flow behavior in modified 9Cr-1Mo steel at room temperature. The aim of these experiments was to determine whether the procedures recommended in NE Standard F9-5T for inelastic design analysis are applicable for this material in normalized and tempered condition. The first experiment investigated small offset yield behavior subsequent to radial preloads (sq rt of 3 sub sigma 12 = sub sigma 11) in tension-torsion stress space. The second experiment investigated yield behavior subsequent to nonradial preloads and also the time-dependent flow occurring during 0.5 hour periods at constant stress. The results of these experiments were qualitatively similar to those obtained earlier for types 304 and 316 stainless steel. Specifically, the von Mises yield criterion was found to provide a reasonable approximation of initial yield behavior. Although the subsequent yield surfaces suffered considerable distortion from their near-circular form after both radial and nonradial preloads, the hardening behavior was to the first order kinematic in nature. The strain-time data obtained during the 0.5 hr hold periods showed characteristics typical of creep curves. As in the case of earlier experiments, the high initial flow rates diminished more rapidly than would be estimated from elevated temperature data.

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

    International Nuclear Information System (INIS)

    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)

  5. Simulation of Complex Cracking in Plain Weave C/SiC Composite under Biaxial Loading

    Science.gov (United States)

    Cheng, Ron-Bin; Hsu, Su-Yuen

    2012-01-01

    Finite element analysis is performed on a mesh, based on computed geometry of a plain weave C/SiC composite with assumed internal stacking, to reveal the pattern of internal damage due to biaxial normal cyclic loading. The simulation encompasses intertow matrix cracking, matrix cracking inside the tows, and separation at the tow-intertow matrix and tow-tow interfaces. All these dissipative behaviors are represented by traction-separation cohesive laws. Not aimed at quantitatively predicting the overall stress-strain relation, the simulation, however, does not take the actual process of fiber debonding into account. The fiber tows are represented by a simple rule-of-mixture model where the reinforcing phase is a hypothetical one-dimensional material. Numerical results indicate that for the plain weave C/SiC composite, 1) matrix-crack initiation sites are primarily determined by large intertow matrix voids and interlayer tow-tow contacts, 2) the pattern of internal damage strongly depends on the loading path and initial stress, 3) compressive loading inflicts virtually no damage evolution. KEY WORDS: ceramic matrix composite, plain weave, cohesive model, brittle failure, smeared crack model, progressive damage, meso-mechanical analysis, finite element.

  6. Practical method for analysis and design of slender reinforced concrete columns subjected to biaxial bending and axial loads

    Science.gov (United States)

    Bouzid, T.; Demagh, K.

    2011-03-01

    Reinforced and concrete-encased composite columns of arbitrarily shaped cross sections subjected to biaxial bending and axial loads are commonly used in many structures. For this purpose, an iterative numerical procedure for the strength analysis and design of short and slender reinforced concrete columns with a square cross section under biaxial bending and an axial load by using an EC2 stress-strain model is presented in this paper. The computational procedure takes into account the nonlinear behavior of the materials (i.e., concrete and reinforcing bars) and includes the second - order effects due to the additional eccentricity of the applied axial load by the Moment Magnification Method. The ability of the proposed method and its formulation has been tested by comparing its results with the experimental ones reported by some authors. This comparison has shown that a good degree of agreement and accuracy between the experimental and theoretical results have been obtained. An average ratio (proposed to test) of 1.06 with a deviation of 9% is achieved.

  7. Spatial filtering efficiency of monostatic biaxial lidar: analysis and applications.

    Science.gov (United States)

    Agishev, Ravil R; Comeron, Adolfo

    2002-12-20

    Results of lidar modeling based on spatial-angular filtering efficiency criteria are presented. Their analysis shows that the low spatial-angular filtering efficiency of traditional visible and near-infrared systems is an important cause of low signal/background-radiation ratio (SBR) at the photodetector input The low SBR may be responsible for considerable measurement errors and ensuing the low accuracy of the retrieval of atmospheric optical parameters. As shown, the most effective protection against sky background radiation for groundbased biaxial lidars is the modifying of their angular field according to a spatial-angular filtering efficiency criterion. Some effective approaches to achieve a high filtering efficiency for the receiving system optimization are discussed. PMID:12510915

  8. Electromagnetic biaxial vector scanner using radial magnetic field.

    Science.gov (United States)

    Han, Aleum; Cho, Ah Ran; Ju, Suna; Ahn, Si-Hong; Bu, Jong-Uk; Ji, Chang-Hyeon

    2016-07-11

    We present an electromagnetic biaxial vector-graphic scanning micromirror. In contrast to conventional electromagnetic actuators using linear magnetic field, proposed device utilizes a radial magnetic field and uniquely designed current paths to enable the 2 degree-of-freedom scanning motion. As the radial field is generated by concentrically assembled magnets placed under the scanner die, large driving torque can be generated without the aid of hermetic packaging and relatively small device volume can be achieved. Mechanical half scan angle of 6.43° and 4.20° have been achieved at DC current of 250mA and 350mA for horizontal and vertical scans, respectively. Forced actuation along both scan axes has been realized by feedback control. PMID:27410851

  9. Characteristics of Plane Wave Propagation in Biaxially Anisotropic Gyrotropic Media

    Institute of Scientific and Technical Information of China (English)

    PAN Wei-Tao; LIU Song-Hua; QIU Zhi-Liang

    2012-01-01

    Propagation characteristics of electromagnetic waves at the interface between an isotropic regular medium and a biaxially anisotropic gyrotropic medium are investigated.The results indicate that the reflection and refract ionproperties of electromagnetic waves are closely dependent on the dispersion relation of the gyrotropic media,and that anomalous total reflection and negative refraction may occur.The existence conditions of total transmission are also considered.It is found that total transmission arises when the TE-polarized incident waves are normal to the interface and the physical parameters of the two media are chosen properly,which are quite different from the existence conditions of total transmission at the anisotropic left-handed material interface.Numerical resul tsare given to validate our theoretical analysis.

  10. Conductive layer for biaxially oriented semiconductor film growth

    Science.gov (United States)

    Findikoglu, Alp T.; Matias, Vladimir

    2007-10-30

    A conductive layer for biaxially oriented semiconductor film growth and a thin film semiconductor structure such as, for example, a photodetector, a photovoltaic cell, or a light emitting diode (LED) that includes a crystallographically oriented semiconducting film disposed on the conductive layer. The thin film semiconductor structure includes: a substrate; a first electrode deposited on the substrate; and a semiconducting layer epitaxially deposited on the first electrode. The first electrode includes a template layer deposited on the substrate and a buffer layer epitaxially deposited on the template layer. The template layer includes a first metal nitride that is electrically conductive and has a rock salt crystal structure, and the buffer layer includes a second metal nitride that is electrically conductive. The semiconducting layer is epitaxially deposited on the buffer layer. A method of making such a thin film semiconductor structure is also described.

  11. Surface polaritons in symmetry planes of biaxial crystals

    Energy Technology Data Exchange (ETDEWEB)

    Furs, A N; Galynsky, V M; Barkovsky, L M [Department of Theoretical Physics, Belarussian State University, Fr. Skarina Ave. 4, Minsk 220050 (Belarus)

    2005-09-16

    The problem of the surface polariton existence in symmetry planes of non-magnetic biaxial crystals is studied theoretically. The plane interface of such a crystal and a semi-infinite isotropic medium is considered. With the use of the integral formalism formulated in our earlier work, the dispersion equation is derived for the polaritons under consideration. The existence conditions for the dispersion equation solutions are obtained in the form of algebraic inequalities for principal values of inverse dielectric permittivity tensors. If these conditions are satisfied, then excitation of surface waves is possible along the allowed propagation directions, which constitute sectors in the interface plane. Exact expressions are obtained that determine location of these sectors with respect to the symmetry axes of the crystal.

  12. DYNAMIC STRAIN MAPPING AND REAL-TIME DAMAGE STATE ESTIMATION UNDER BIAXIAL RANDOM FATIGUE LOADING

    Data.gov (United States)

    National Aeronautics and Space Administration — DYNAMIC STRAIN MAPPING AND REAL-TIME DAMAGE STATE ESTIMATION UNDER BIAXIAL RANDOM FATIGUE LOADING SUBHASISH MOHANTY*, ADITI CHATTOPADHYAY, JOHN N. RAJADAS, AND...

  13. On the sensitivity of directions which support Voigt wave propagation in infiltrated biaxial dielectric materials

    CERN Document Server

    Mackay, Tom G

    2013-01-01

    Voigt wave propagation (VWP) was considered in a porous biaxial dielectric material which was infiltrated with a material of refractive index $n_a$. The infiltrated material was regarded as a homogenized composite material in the long-wavelength regime and its constitutive parameters were estimated using the extended Bruggeman homogenization formalism. In our numerical studies, the directions which support VWP were found to vary by as much as $300^\\circ$ per RIU as the refractive index $n_a$ was varied. The sensitivities achieved were acutely dependent upon the refractive index $n_a$ and the degrees of anisotropy and dissipation of the porous biaxial material. The orientations, shapes and sizes of the particles which constitute the infiltrating material and the porous biaxial material exerted only a secondary influence on the maximum sensitivities achieved. Also, for the parameter ranges considered, the degree of porosity of the biaxial material had little effect on the maximum sensitivities achieved. These n...

  14. Maier-Saupe model for a mixture of uniaxial and biaxial molecules

    Science.gov (United States)

    Nascimento, E. S.; Henriques, E. F.; Vieira, A. P.; Salinas, S. R.

    2015-12-01

    We introduce shape variations in a liquid-crystalline system by considering an elementary Maier-Saupe lattice model for a mixture of uniaxial and biaxial molecules. Shape variables are treated in the annealed (thermalized) limit. We analyze the thermodynamic properties of this system in terms of temperature T , concentration c of intrinsically biaxial molecules, and a parameter Δ associated with the degree of biaxiality of the molecules. At the mean-field level, we use standard techniques of statistical mechanics to draw global phase diagrams, which are shown to display a rich structure, including uniaxial and biaxial nematic phases, a reentrant ordered region, and many distinct multicritical points. Also, we use the formalism to write an expansion of the free energy in order to make contact with the Landau-de Gennes theory of nematic phase transitions.

  15. Suspended germanium cross-shaped microstructures for enhancing biaxial tensile strain

    Science.gov (United States)

    Ishida, Satomi; Kako, Satoshi; Oda, Katsuya; Ido, Tatemi; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2016-04-01

    We fabricate a suspended germanium cross-shaped microstructure to biaxially enhance residual tensile strain using a germanium epilayer directly grown on a silicon-on-insulator substrate. Such a suspended germanium system with enhanced biaxial tensile strain will be a promising platform for incorporating optical cavities toward the realization of germanium lasers. We demonstrate systematic control over biaxial tensile strain and photoluminescence peaks by changing structural geometry. The photoluminescence peaks corresponding to the direct recombination between the conduction Γ valley and two strain-induced separated valence bands have been clearly assigned. A maximum biaxial strain of 0.8% has been achieved, which is almost half of that required to transform germanium into a direct band-gap semiconductor.

  16. Comparative efficiency analysis of different nonlinear modelling strategies to simulate the biaxial response of RC columns

    OpenAIRE

    Hugo Rodrigues; Humberto Varum; Antonio Arede; Anibal Costa

    2012-01-01

    The performance of different nonlinear modelling strategies to simulate the response of RC columns subjected to axial load combined with cyclic biaxial horizontal loading is compared. The models studied are classified into two categories according to the nonlinearity distribution assumed in the elements: lumped-plasticity and distributed inelasticity. For this study, results of tests on 24 columns subjected to cyclic uniaxial and biaxial lateral displacements were numerically reproduced. The ...

  17. Two-Particle Cluster Theory for Biaxial Nematic Phase Based on a Recently Proposed Interaction Potential

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Dong; ZHANG Yan-Jun; SUN Zong-Li

    2006-01-01

    @@ Two-particle cluster theory is applied to study the biaxial nematic phase formed by biaxial molecules interacting with a simplified model proposed by Sonnet et al. [Phys. Rev. E 67 (2003) 061701]. For the temperature dependences of the internal energy per particle and of the order parameters, the two-particle theory yields an improved result compared with mean field theory. Concerning the phase diagram, the two-particle theory gives the numerical result in qualitative agreement with the mean field theory.

  18. Fatigue Test Design: Scenarios for Biaxial Fatigue Testing of a 60-Meter Wind Turbine Blade

    Energy Technology Data Exchange (ETDEWEB)

    Post, Nathan [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-07-01

    Current practice in commercial certification of wind turbine blades is to perform separate flap and lead-lag fatigue tests. The National Renewable Energy Laboratory has been researching and evaluating biaxial fatigue testing techniques and demonstrating various options, typically on smaller-scale test articles at the National Wind Technology Center. This report evaluates some of these biaxial fatigue options in the context of application to a multimegawatt blade certification test program at the Wind Technology Testing Center in Charlestown, Massachusetts.

  19. Biaxial-Type Concentrated Solar Tracking System with a Fresnel Lens for Solar-Thermal Applications

    OpenAIRE

    Tsung Chieh Cheng; Chao Kai Yang; Lin, I.

    2016-01-01

    In this paper, an electromechanical, biaxial-type concentrated solar tracking system was designed for solar-thermal applications. In our tracking system, the sunlight was concentrated by the microstructure of Fresnel lens to the heating head of the Stirling engine and two solar cells were installed to provide the power for tracking system operation. In order to obtain the maximum sun power, the tracking system traces the sun with the altitude-azimuth biaxial tracing method and accurately main...

  20. Optimal design and examination study of biaxial tensile specimens for solid propellant%固体推进剂双向拉伸试件优化设计及试验

    Institute of Scientific and Technical Information of China (English)

    贾永刚; 张为华; 张炜

    2011-01-01

    基于Kelly提出的十字形试件,设计了一种新型固体推进剂双向拉伸试件。利用ANSYS有限元软件对试件双向加载过程试验区中引起的应力应变的数值模拟,实现了十字形试件的优化设计,经过优化的试件在满足双轴试验要求方面有了明显的改进。通过对丁羟复合固体推进剂试件双向加载力学行为试验研究,获得不同拉伸速率双向拉伸应力—应变破坏曲线,为推进剂材料破坏分析的经验准则提供判据。结果表明,固体推进剂断裂延伸率的双向弱化效应很明显,双向加载比例为等双拉状态时,其双向断裂延伸率比单向断裂延伸率降低37.5%。%A new-style biaxial tensile specimen of solid propellant is designed,based on the cruciform specimens proposed by Kelly.By using the finite element analysis ANSYS,the stress and displacement of specimens in the test section is simulated and the optimization of the cruciform specimens is realized.The stress and displacement fields in the central test section exhibit an excellent homogeneity and the maximum equivalent Von-Mises stress corresponding to the central part of the test section.In particular,the mechanical behavior of the biaxial tensile for HTPB propellant are tested,and the stress-strain wreck curves of biaxial tension are obtained under different tension speed.These data offer criterion for the wreck analysis of propellant material.The results show that the biaxial weakening of solid propellant is remarkable,and the Von-Mises rupture elongation of biaxial tensile decline about 37.5% to uniaxial tensile while the biaxial loads are equivalent.

  1. Phase diagram of the uniaxial and biaxial soft-core Gay-Berne model

    Science.gov (United States)

    Berardi, Roberto; Lintuvuori, Juho S.; Wilson, Mark R.; Zannoni, Claudio

    2011-10-01

    Classical molecular dynamics simulations have been used to explore the phase diagrams for a family of attractive-repulsive soft-core Gay-Berne models [R. Berardi, C. Zannoni, J. S. Lintuvuori, and M. R. Wilson, J. Chem. Phys. 131, 174107 (2009)] and determine the effect of particle softness, i.e., of a moderately repulsive short-range interaction, on the order parameters and phase behaviour of model systems of uniaxial and biaxial ellipsoidal particles. We have found that isotropic, uniaxial, and biaxial nematic and smectic phases are obtained for the model. Extensive calculations of the nematic region of the phase diagram show that endowing mesogenic particles with such soft repulsive interactions affect the stability range of the nematic phases, and in the case of phase biaxiality it also shifts it to lower temperatures. For colloidal particles, stabilised by surface functionalisation, (e.g., with polymer chains), we suggest that it should be possible to tune liquid crystal behaviour to increase the range of stability of uniaxial and biaxial phases (by varying solvent quality). We calculate second virial coefficients and show that they are a useful means of characterising the change in effective softness for such systems. For thermotropic liquid crystals, the introduction of softness in the interactions between mesogens with overall biaxial shape (e.g., through appropriate conformational flexibility) could provide a pathway for the actual chemical synthesis of stable room-temperature biaxial nematics.

  2. Stress

    Science.gov (United States)

    ... Some people experience digestive symptoms. Others may have headaches, sleeplessness, depressed mood, anger, and irritability. People under chronic stress get more frequent and severe viral infections, such ...

  3. Prediction of crack growth direction by Strain Energy Sih's Theory on specimens SEN under tension-compression biaxial loading employing Genetic Algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-MartInez R; Lugo-Gonzalez E; Urriolagoitia-Calderon G; Urriolagoitia-Sosa G; Hernandez-Gomez L H; Romero-Angeles B; Torres-San Miguel Ch, E-mail: rrodriguezm@ipn.mx, E-mail: urrio332@hotmail.com, E-mail: guiurri@hotmail.com, E-mail: luishector56@hotmail.com, E-mail: romerobeatriz98@hotmail.com, E-mail: napor@hotmail.com [INSTITUTO POLITECNICO NACIONAL Seccion de Estudios de Posgrado e Investigacion (SEPI), Escuela Superior de Ingenieria Mecanica y Electrica (ESIME), Edificio 5. 2do Piso, Unidad Profesional Adolfo Lopez Mateos ' Zacatenco' Col. Lindavista, C.P. 07738, Mexico, D.F. (Mexico)

    2011-07-19

    Crack growth direction has been studied in many ways. Particularly Sih's strain energy theory predicts that a fracture under a three-dimensional state of stress spreads in direction of the minimum strain energy density. In this work a study for angle of fracture growth was made, considering a biaxial stress state at the crack tip on SEN specimens. The stress state applied on a tension-compression SEN specimen is biaxial one on crack tip, as it can observed in figure 1. A solution method proposed to obtain a mathematical model considering genetic algorithms, which have demonstrated great capacity for the solution of many engineering problems. From the model given by Sih one can deduce the density of strain energy stored for unit of volume at the crack tip as dW = [1/2E({sigma}{sup 2}{sub x} + {sigma}{sup 2}{sub y}) - {nu}/E({sigma}{sub x}{sigma}{sub y})]dV (1). From equation (1) a mathematical deduction to solve in terms of {theta} of this case was developed employing Genetic Algorithms, where {theta} is a crack propagation direction in plane x-y. Steel and aluminium mechanical properties to modelled specimens were employed, because they are two of materials but used in engineering design. Obtained results show stable zones of fracture propagation but only in a range of applied loading.

  4. Cyclic plasticity of an austenitic-ferritic stainless steel under biaxial non proportional loading

    International Nuclear Information System (INIS)

    Austenitic-ferritic stainless steels are supplied since about 30 years only, so they are yet not well-known. Their behaviour in cyclic plasticity was studied under uniaxial loading but not under multiaxial loading, whereas only a thorough knowledge of the phenomena influencing the mechanical behaviour of a material enables to simulate and predict accurately its behaviour in a structure. This work aims to study and model the behaviour of a duplex stainless steel under cyclic biaxial loading. A three step method was adopted. A set of tension-torsion tests on tubular specimen was first defined. We studied the equivalence between loading directions, and then the influence of loading path and loading history on the stress response of the material. Results showed that duplex stainless steel shows an extra-hardening under non proportional loading and that its behaviour depends on previous loading. Then, in order to analyse the results obtained during this first experimental stage, the yield surface was measured at different times during cyclic loading of the same kind. A very small plastic strain offset (2*10-5) was used in order not to disturb the yield surface measured. The alteration of isotropic and kinematic hardening variables were deduced from these measures. Finally, three phenomenological constitutive laws were identified with the experimental set. We focused our interest on the simulation of stabilized stress levels and on the simulation of the cyclic hardening/softening behaviour. The comparison between experimental and numerical results enabled the testing of the relevance of these models. (authors)

  5. Preparation of biaxially oriented TlCu-1234 thin films

    CERN Document Server

    Khan, N A; Tateai, F; Kojima, T; Ishida, K; Terada, N; Ihara, H

    1999-01-01

    The single phase of TlCu-1234 superconductor thin films is prepared for the first time by the amorphous phase epitaxy (APE) method, which is thallium treatment of sputtered amorphous phase at 900 degrees C for 1 h. The amorphous $9 phase is prepared by sputtering from the stoichiometric target composition CuBa/sub 2/Ca/sub 3/Cu/sub 4/O/sub 12-y/. The films on the SrTiO/sub 3/ substrate are aligned biaxially after the thallium treatment. Highly reproducible $9 TlCu-1234 films are prepared by this method. The XRD reflected a predominant single phase with the c-axis lattice constant of 18.74 AA. This lattice constant value is in between that of Cu-1234 (17.99 AA) and Tl-1234 (19.11 AA) . The $9 pole figure measurements of (103) reflection of the films showed a-axis-oriented crystals with Delta phi =0.8 degrees . The composition of the films after energy dispersive X-ray (EDX) measurements is Tl/sub 0.8/Cu/sub 0.2/Ba/sub $9 2/Ca/sub 3/Cu/sub 4/O /sub 12-y/. From the resistivity measurements, the T/sub c/ is 113 K...

  6. Atomic force microscopy study of biaxially oriented polypropylene films

    Science.gov (United States)

    Nie, H.-Y.; Walzak, M. J.; McIntyre, N. S.

    2004-08-01

    Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space morphological information of solid surfaces. AFM was used in this study to image the surface morphology of a biaxially oriented polypropylene film. The polymer film is characterized by a nanometer-scale, fiberlike network structure, which reflects the drawing process used during the fabrication of the film. AFM was used to study polymer-surface treatment to improve wettability by exposing the polymer to ozone with or without ultraviolet (UV) irradiation. Surface-morphology changes observed by AFM are the result of the surface oxidation induced by the treatment. Due to the topographic features of the polymer film, the fiberlike structure has been used to check the performance of the AFM tip. An AFM image is a mixture of the surface morphology and the shape of the AFM tip. Therefore, it is important to check the performance of a tip to ensure that the AFM image collected reflects the true surface features of the sample, rather than contamination on the AFM tip.

  7. Electret properties of biaxially stretched polypropylene films containing various additives

    Energy Technology Data Exchange (ETDEWEB)

    Hillenbrand, J [Institute for Communications Technology, Darmstadt University of Technology, 64283 Darmstadt (Germany); Behrendt, N [Polymer Engineering, University of Bayreuth, 95447 Bayreuth (Germany); Altstaedt, V [Polymer Engineering, University of Bayreuth, 95447 Bayreuth (Germany); Schmidt, H-W [Macromolecular Chemistry I, University of Bayreuth, 95447 Bayreuth (Germany); Sessler, G M [Institute for Communications Technology, Darmstadt University of Technology, 64283 Darmstadt (Germany)

    2006-02-07

    Isotactic polypropylene (i-PP) films containing additives such as the commercial {alpha} -nucleation agent NA11 and the anorganic filler particles CaCO{sub 3} and Al{sub 2}O{sub 3} were biaxially stretched. As a result, the films assume a cellular morphology with oblong cavities extending in the direction of the film elongation. In the present study, stretched films of 50 {mu}m thickness with additive concentrations of 0.05-10 mass per cent were charged with a corona method to potentials of 400 or 500 V. The stability of the charges was tested isothermally at temperatures of 90 and 120 deg. C and by means of thermally stimulated discharge (TSD) experiments. The isothermal measurements show, for the above additives with concentrations higher than about 0.3%, a reduction of the charge decay with increasing additive concentrations. Compared with reference films of pure PP, the potential decay of the films containing additive concentrations of 10% is significantly reduced. Correspondingly, the TSD measurements indicate a shift of the main discharge peak to higher temperatures up to the melting temperature. Generally, the voiding and thus the stability also increases with the stretching ratio. These improvements of the charge stability are attributed to the barrier effect of the cavities. The results are of interest with respect to the various applications of PP electrets, such as ferroelectret devices and air filters.

  8. Electret properties of biaxially stretched polypropylene films containing various additives

    Science.gov (United States)

    Hillenbrand, J.; Behrendt, N.; Altstädt, V.; Schmidt, H.-W.; Sessler, G. M.

    2006-02-01

    Isotactic polypropylene (i-PP) films containing additives such as the commercial α -nucleation agent NA11 and the anorganic filler particles CaCO3 and Al2O3 were biaxially stretched. As a result, the films assume a cellular morphology with oblong cavities extending in the direction of the film elongation. In the present study, stretched films of 50 µm thickness with additive concentrations of 0.05-10 mass per cent were charged with a corona method to potentials of 400 or 500 V. The stability of the charges was tested isothermally at temperatures of 90 and 120 °C and by means of thermally stimulated discharge (TSD) experiments. The isothermal measurements show, for the above additives with concentrations higher than about 0.3%, a reduction of the charge decay with increasing additive concentrations. Compared with reference films of pure PP, the potential decay of the films containing additive concentrations of 10% is significantly reduced. Correspondingly, the TSD measurements indicate a shift of the main discharge peak to higher temperatures up to the melting temperature. Generally, the voiding and thus the stability also increases with the stretching ratio. These improvements of the charge stability are attributed to the barrier effect of the cavities. The results are of interest with respect to the various applications of PP electrets, such as ferroelectret devices and air filters.

  9. 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....

  10. An anisotropic hyperelastic constitutive model of brain white matter in biaxial tension and structural-mechanical relationships.

    Science.gov (United States)

    Labus, Kevin M; Puttlitz, Christian M

    2016-09-01

    Computational models of the brain require accurate and robust constitutive models to characterize the mechanical behavior of brain tissue. The anisotropy of white matter has been previously demonstrated; however, there is a lack of data describing the effects of multi-axial loading, even though brain tissue experiences multi-axial stress states. Therefore, a biaxial tensile experiment was designed to more fully characterize the anisotropic behavior of white matter in a quasi-static loading state, and the mechanical data were modeled with an anisotropic hyperelastic continuum model. A probabilistic analysis was used to quantify the uncertainty in model predictions because the mechanical data of brain tissue can show a high degree of variability, and computational studies can benefit from reporting the probability distribution of model responses. The axonal structure in white matter can be heterogeneous and regionally dependent, which can affect computational model predictions. Therefore, corona radiata and corpus callosum regions were tested, and histology and transmission electron microscopy were performed on tested specimens to relate the distribution of axon orientations and the axon volume fraction to the mechanical behavior. These measured properties were implemented into a structural constitutive model. Results demonstrated a significant, but relatively low anisotropic behavior, yet there were no conclusive mechanical differences between the two regions tested. The inclusion of both biaxial and uniaxial tests in model fits improved the accuracy of model predictions. The mechanical anisotropy of individual specimens positively correlated with the measured axon volume fraction, and, accordingly, the structural model exhibited slightly decreased uncertainty in model predictions compared to the model without structural properties. PMID:27214689

  11. An anisotropic hyperelastic constitutive model of brain white matter in biaxial tension and structural-mechanical relationships.

    Science.gov (United States)

    Labus, Kevin M; Puttlitz, Christian M

    2016-09-01

    Computational models of the brain require accurate and robust constitutive models to characterize the mechanical behavior of brain tissue. The anisotropy of white matter has been previously demonstrated; however, there is a lack of data describing the effects of multi-axial loading, even though brain tissue experiences multi-axial stress states. Therefore, a biaxial tensile experiment was designed to more fully characterize the anisotropic behavior of white matter in a quasi-static loading state, and the mechanical data were modeled with an anisotropic hyperelastic continuum model. A probabilistic analysis was used to quantify the uncertainty in model predictions because the mechanical data of brain tissue can show a high degree of variability, and computational studies can benefit from reporting the probability distribution of model responses. The axonal structure in white matter can be heterogeneous and regionally dependent, which can affect computational model predictions. Therefore, corona radiata and corpus callosum regions were tested, and histology and transmission electron microscopy were performed on tested specimens to relate the distribution of axon orientations and the axon volume fraction to the mechanical behavior. These measured properties were implemented into a structural constitutive model. Results demonstrated a significant, but relatively low anisotropic behavior, yet there were no conclusive mechanical differences between the two regions tested. The inclusion of both biaxial and uniaxial tests in model fits improved the accuracy of model predictions. The mechanical anisotropy of individual specimens positively correlated with the measured axon volume fraction, and, accordingly, the structural model exhibited slightly decreased uncertainty in model predictions compared to the model without structural properties.

  12. Control of biaxial strain in single-layer molybdenite using local thermal expansion of the substrate

    Science.gov (United States)

    Plechinger, Gerd; Castellanos-Gomez, Andres; Buscema, Michele; van der Zant, Herre S. J.; Steele, Gary A.; Kuc, Agnieszka; Heine, Thomas; Schüller, Christian; Korn, Tobias

    2015-03-01

    Single-layer MoS2 is a direct-gap semiconductor whose electronic band structure strongly depends on the strain applied to its crystal lattice. While uniaxial strain can be easily applied in a controlled way, e.g., by bending of a flexible substrate with the atomically thin MoS2 layer on top, experimental realization of biaxial strain is more challenging. Here, we exploit the large mismatch between the thermal expansion coefficients of MoS2 and a silicone-based substrate to apply a controllable biaxial tensile strain by heating the substrate with a focused laser. The effect of this biaxial strain is directly observable in optical spectroscopy as a redshift of the MoS2 photoluminescence. We also demonstrate the potential of this method to engineer more complex strain patterns by employing highly absorptive features on the substrate to achieve non-uniform heat profiles. By comparison of the observed redshift to strain-dependent band structure calculations, we estimate the biaxial strain applied by the silicone-based substrate to be up to 0.2%, corresponding to a band gap modulation of 105 meV per percentage of biaxial tensile strain.

  13. Modeling of biaxial gimbal-less MEMS scanning mirrors

    Science.gov (United States)

    von Wantoch, Thomas; Gu-Stoppel, Shanshan; Senger, Frank; Mallas, Christian; Hofmann, Ulrich; Meurer, Thomas; Benecke, Wolfgang

    2016-03-01

    One- and two-dimensional MEMS scanning mirrors for resonant or quasi-stationary beam deflection are primarily known as tiny micromirror devices with aperture sizes up to a few Millimeters and usually address low power applications in high volume markets, e.g. laser beam scanning pico-projectors or gesture recognition systems. In contrast, recently reported vacuum packaged MEMS scanners feature mirror diameters up to 20 mm and integrated high-reflectivity dielectric coatings. These mirrors enable MEMS based scanning for applications that require large apertures due to optical constraints like 3D sensing or microscopy as well as for high power laser applications like laser phosphor displays, automotive lighting and displays, 3D printing and general laser material processing. This work presents modelling, control design and experimental characterization of gimbal-less MEMS mirrors with large aperture size. As an example a resonant biaxial Quadpod scanner with 7 mm mirror diameter and four integrated PZT (lead zirconate titanate) actuators is analyzed. The finite element method (FEM) model developed and computed in COMSOL Multiphysics is used for calculating the eigenmodes of the mirror as well as for extracting a high order (n < 10000) state space representation of the mirror dynamics with actuation voltages as system inputs and scanner displacement as system output. By applying model order reduction techniques using MATLABR a compact state space system approximation of order n = 6 is computed. Based on this reduced order model feedforward control inputs for different, properly chosen scanner displacement trajectories are derived and tested using the original FEM model as well as the micromirror.

  14. Tuning magnetism by biaxial strain in native ZnO.

    Science.gov (United States)

    Peng, Chengxiao; Wang, Yuanxu; Cheng, Zhenxiang; Zhang, Guangbiao; Wang, Chao; Yang, Gui

    2015-07-01

    Magnetic ZnO, one of the most important diluted magnetic semiconductors (DMS), has attracted great scientific interest because of its possible technological applications in optomagnetic devices. Magnetism in this material is usually delicately tuned by the doping level, dislocations, and local structures. The rational control of magnetism in ZnO is a highly attractive approach for practical applications. Here, the tuning effect of biaxial strain on the d(0) magnetism of native imperfect ZnO is demonstrated through first-principles calculations. Our calculation results show that strain conditions have little effect on the defect formation energy of Zn and O vacancies in ZnO, but they do affect the magnetism significantly. For a cation vacancy, increasing the compressive strain will obviously decrease its magnetic moment, while tensile strain cannot change the moment, which remains constant at 2 μB. For a singly charged anion vacancy, however, the dependence of the magnetic moment on strain is opposite to that of the Zn vacancy. Furthermore, the ferromagnetic state is always present, irrespective of the strain type, for ZnO with two zinc vacancies, 2VZns. A large tensile strain is favorable for improving the Curie temperature and realizing room temperature ferromagnetism for ZnO-based native semiconductors. For ZnO with two singly charged oxygen vacancies, 2Vs, no ferromagnetic ordering can be observed. Our work points the way to the rational design of materials beyond ZnO with novel non-intrinsic functionality by simply tuning the strain in a thin film form.

  15. Biaxial tensile tests identify epidermis and hypodermis as the main structural elements of sweet cherry skin.

    Science.gov (United States)

    Brüggenwirth, Martin; Fricke, Heiko; Knoche, Moritz

    2014-01-01

    The skin of developing soft and fleshy fruit is subjected to considerable growth stress, and failure of the skin is associated with impaired barrier properties in water transport and pathogen defence. The objectives were to establish a standardized, biaxial tensile test of the skin of soft and fleshy fruit and to use it to characterize and quantify mechanical properties of the sweet cherry (Prunus avium) fruit skin as a model. A segment of the exocarp (ES) comprising cuticle, epidermis, hypodermis and adhering flesh was mounted in the elastometer such that the in vivo strain was maintained. The ES was pressurized from the inner surface and the pressure and extent of associated bulging were recorded. Pressure : strain responses were almost linear up to the point of fracture, indicating that the modulus of elasticity was nearly constant. Abrading the cuticle decreased the fracture strain but had no effect on the fracture pressure. When pressure was held constant, bulging of the ES continued to increase. Strain relaxation upon releasing the pressure was complete and depended on time. Strains in longitudinal and latitudinal directions on the bulging ES did not differ significantly. Exocarp segments that released their in vivo strain before the test had higher fracture strains and lower moduli of elasticity. The results demonstrate that the cherry skin is isotropic in the tangential plane and exhibits elastic and viscoelastic behaviour. The epidermis and hypodermis, but not the cuticle, represent the structural 'backbone' in a cherry skin. This test is useful in quantifying the mechanical properties of soft and fleshy fruit of a range of species under standardized conditions. PMID:24876301

  16. Liquid crystal display modes in a nontilted bent-core biaxial smectic liquid crystal

    Science.gov (United States)

    Nagaraj, Mamatha; Panarin, Y. P.; Vij, J. K.; Keith, C.; Tschierske, C.

    2010-11-01

    Liquid crystal display (LCD) modes associated with the rotation of the secondary director in nontilted, biaxial smectic phase of an achiral bent-core compound are demonstrated. For LCDs, we find that at least four display modes are possible using SmAPA phase of the studied material, in which the minor directors in adjacent layers are aligned antiferroelectrically. The advantages of these modes include low driving field (1-2 V/μm), high contrast ratio 1000:1, relatively fast switching time of 0.5 ms and continuous gray scale. The molecular short axis or the polar axis in a negative dielectric, biaxial material is oriented by the in-plane electric field by a combination dielectric biaxiality and polarity at low electric fields and polarity at higher fields.

  17. The elusive thermotropic biaxial nematic phase in rigid bent-core molecules

    Indian Academy of Sciences (India)

    Bharat R Acharya; Andrew Primak; Theo J Dingemans; Edward T Samulski; Satyendra Kumar

    2003-08-01

    The biaxial nematic liquid crystalline phase was predicted several decades ago. Several vigorous attempts to find it in various systems resulted in mis-identifications. The results of X-ray diffraction and optical texture studies of the phases exhibited by rigid bent-core molecules derived from 2,5-bis-(-hydroxyphenyl)-1,3,4-oxadiazole reveal that the biaxial nematic phase is formed by three compounds of this type. X-ray diffraction studies reveal that the nematic phase of these compounds has the achiral symmetry D2h, in which the overall long axes of the molecules are oriented parallel to each other to define the major axis of the biaxial phase. The apex of the bent-cores defines the minor axis of this phase along which the planes containing the bent-cores of neighboring molecules are oriented parallel to each other.

  18. Formability and cavitation behavior of superplastic AA5083 aluminum alloy under biaxial tension

    Institute of Scientific and Technical Information of China (English)

    LUO Ying-bing; LI Da-yong; PENG Ying-hong

    2006-01-01

    The superplastic forming potential of two fine-grained 5083 aluminum alloys were studied under biaxial tension using a pneumatic bulge test. Experiments were performed at temperatures ranging from 475 to 525 ℃ with three different strain paths ranging from equi-biaxial to approaching plane strain. The shape of the forming limited diagram(FLD) is found to be significantly different from FLDs commonly used in room temperature stamping. The effects of temperature on final thickness distribution, dome height and cavitation were investigated for the case of equi-biaxial stretching. Increasing temperature in free bulge forming can improve the thickness distribution of final parts but have no significant effect on dome height. The results indicate that determination of forming limits in SPF cannot be represented with a simple FLD and additional metrics such as external thinning and internal cavitation needed to determine the SPF potential of a material.

  19. Formation of biaxially textured molybdenum thin films under the influence of recrystallization conditions

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, Rahul, E-mail: krishr2@rpi.edu [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Riley, Michael [Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Lee, Sabrina [US Army Armament Research, Development and Engineering Center, Benet Labs, Watervliet, NY 12189 (United States); Lu, Toh-Ming [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)

    2011-06-01

    This article highlights the formation of biaxially textured body centered cubic Mo nanorods under recrystallization conditions using glancing angle deposition. The flux incidence angle has been changed ({alpha} = 0 deg., 70 deg. and 85 deg. away from the surface normal) to observe its effect on the formation of biaxial texture under a constant low Ar pressure environment (0.306 Pa). Only at a glancing flux incidence ({alpha} = 85 deg.), the directional diffusion overcomes the effect of recrystallization to yield a highly biaxial texture. In another study, a normal flux incidence ({alpha} = 0 deg.) was kept constant and the Ar pressure was changed (0.67, 1.33 and 2.67 Pa) to see its influence on the film morphology and the resulting texture. The Ar pressure variation was aimed at attempting a zone transformation in accordance with the structure zone model. While the morphology appeared to agree with the expected zone transformation, the texture did not.

  20. Biaxial Stretch Improves Elastic Fiber Maturation, Collagen Arrangement, and Mechanical Properties in Engineered Arteries.

    Science.gov (United States)

    Huang, Angela H; Balestrini, Jenna L; Udelsman, Brooks V; Zhou, Kevin C; Zhao, Liping; Ferruzzi, Jacopo; Starcher, Barry C; Levene, Michael J; Humphrey, Jay D; Niklason, Laura E

    2016-06-01

    Tissue-engineered blood vessels (TEVs) are typically produced using the pulsatile, uniaxial circumferential stretch to mechanically condition and strengthen the arterial grafts. Despite improvements in the mechanical integrity of TEVs after uniaxial conditioning, these tissues fail to achieve critical properties of native arteries such as matrix content, collagen fiber orientation, and mechanical strength. As a result, uniaxially loaded TEVs can result in mechanical failure, thrombus, or stenosis on implantation. In planar tissue equivalents such as artificial skin, biaxial loading has been shown to improve matrix production and mechanical properties. To date however, multiaxial loading has not been examined as a means to improve mechanical and biochemical properties of TEVs during culture. Therefore, we developed a novel bioreactor that utilizes both circumferential and axial stretch that more closely simulates loading conditions in native arteries, and we examined the suture strength, matrix production, fiber orientation, and cell proliferation. After 3 months of biaxial loading, TEVs developed a formation of mature elastic fibers that consisted of elastin cores and microfibril sheaths. Furthermore, the distinctive features of collagen undulation and crimp in the biaxial TEVs were absent in both uniaxial and static TEVs. Relative to the uniaxially loaded TEVs, tissues that underwent biaxial loading remodeled and realigned collagen fibers toward a more physiologic, native-like organization. The biaxial TEVs also showed increased mechanical strength (suture retention load of 303 ± 14.53 g, with a wall thickness of 0.76 ± 0.028 mm) and increased compliance. The increase in compliance was due to combinatorial effects of mature elastic fibers, undulated collagen fibers, and collagen matrix orientation. In conclusion, biaxial stretching is a potential means to regenerate TEVs with improved matrix production, collagen organization, and mechanical

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

    Science.gov (United States)

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

    2016-08-01

    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 (σ2/σ1 = 0) to "near-equibiaxial" tension (σ2/σ1 = 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.

  2. Behavior of reinforced concrete slabs subjected to combined punching shear and biaxial tension

    International Nuclear Information System (INIS)

    This investigation was a continuing study of peripheral (punching) shear strength of precracked, biaxially tensioned, orthogonally reinforced concrete slabs. This research was motivated by the need to determie the strength of a reinforced concrete containment vessel wall when subjected to combined internal pressure and punching shear loads normal to the wall. The study served to determine the effect of three major variables (shear span, size of loaded area, and reinforcing steel ratio) on punching shear strength of slabs that were precracked in biaxial tension and then held at one of the two tension levels (0 or 0.8f/sub y/) during shear load application

  3. Scratch resistance anisotropy in biaxially oriented polypropylene and poly(ethylene terephthalate) films

    Science.gov (United States)

    Nie, H.-Y.; Walzak, M. J.; McIntyre, N. S.

    2006-12-01

    Using a diamond-tipped stylus, scratch tests were conducted on biaxially oriented polypropylene and poly(ethylene terephthalate) films in the two draw directions, i.e., the machine-direction (MD) and the transverse-direction (TD) along which the draw ratios are different. Atomic force microscopy study of those scratches revealed a significant anisotropy in the scratch resistance between the MD and TD for both of the polymer films. We confirmed that the scratch resistance of polymer strands is closely related to the draw ratios, which determine the mechanical strength and optical clarity of biaxially oriented polymer films.

  4. Effective-Field Theory on High Spin Systems with Biaxial Crystal Field

    Institute of Scientific and Technical Information of China (English)

    JIANG Wei; GUO An-Bang; LI Xin; WANG Xi-Kun; BAI Bao-Dong

    2006-01-01

    Based on the effective-field theory with self-spin correlations and the differential operator technique,physical properties of the spin-2 system with biaxial crystal field on the simple cubic, body-centered cubic, as well as faced-centered lattice have been studied. The influences of the external longitudinal magnetic field on the magnetization,internal energy, specific heat, and susceptibility have been discussed in detail. The phenomenon that the magnetization in the ground state shows quantum effects produced by the biaxial transverse crystal field has been found.

  5. Electronic and optical properties of kesterite Cu2ZnSnS4 under in-plane biaxial strains: First-principles calculations

    International Nuclear Information System (INIS)

    The electronic structures and optical properties of Cu2ZnSnS4 (CZTS) under in-plane biaxial strain were systematically investigated using first-principles calculations based on generalized gradient approximation and hybrid functional method, respectively. It is found that the fundamental bandgap at the Γ point decreases linearly with increasing tensile biaxial strain perpendicular to c-axis. However, a bandgap maximum occurs as the compressive biaxial strain is 1.5%. Further increase of compressive strain decreases the bandgap. In addition, the optical properties of CZTS under biaxial strain are also calculated, and the variation trend of optical bandgap with biaxial strain is consistent with the fundamental bandgap.

  6. Characteristics of residual stresses of water jet peened stainless steel

    International Nuclear Information System (INIS)

    The material of the specimen was austenitic stainless steel, SUS316L. The residual stresses in the specimen was introduced by a water jet peening (WJP). The change in the residual stress with thermal aging at 773K was measured by an X-ray stress measurement. The WJP residual stresses were an equi-biaxial stress state, and the compressive residual stress did not decrease against the thermal aging. To investigate dependence of the residual stress on a lattice plane, the WJP residual stresses were measured using hard synchrotron X-rays. (author)

  7. Numerical Investigations on the Influence of Superimposed Double-Sided Pressure on the Formability of Biaxially Stretched AA6111-T4 Sheet Metal

    Science.gov (United States)

    Liu, Jianguang; Wang, Zhongjin; Meng, Qingyuan

    2012-04-01

    Lightweight materials have been widely used in aerospace, automobile industries to meet the requirement of structural weight reduction. Due to their limited plasticity at room temperature, however, lightweight materials always exhibit distinctly poor forming capability in comparison with conventional deep drawing steels. Based on the phenomenon that the superimposed hydrostatic pressure can improve the plasticity of metal, many kinds of double-sided pressure forming processes have been proposed. In the present study, the Gurson-Tvergaard-Needleman (GTN) damage model combined with finite element method is used to investigate the influence of double-sided pressure on the deformation behavior of biaxially stretched AA6111-T4 sheet metal, including nucleation and growth of microvoids, evaluation of stress triaxiality, and so forth. The Marciniak-Kuczynski (M-K) localized necking model is used to predict the right-hand side of the forming limit diagram (FLD) of sheet metal under superimposed double-sided pressure. It is found that the superimposed double-sided pressure has no obvious effect on the nucleation of microvoids. However, the superimposed double-sided pressure can suppress the growth and coalescence of microvoids. The forming limit curve (FLC) of the biaxially stretched AA6111-T4 sheet metal under the superimposed double-sided pressure is improved and the fracture locus shifts to the left. Furthermore, the formability increase value is sensitive to the strain path.

  8. The effect of biaxial strain on impurity diffusion in Si and SiGe

    DEFF Research Database (Denmark)

    Larsen, Arne Nylandsted; Zangenberg, Nikolaj; Fage-Pedersen, Jacob

    2005-01-01

    Results from diffusion studies of different impurities in biaxially strained Si and Si"1"-"xGe"x for low x-values will be presented. The structures are all molecular-beam epitaxy (MBE) grown on strain-relaxed Si"1"-"xGe"x layers, and the impurity profiles are introduced during growth. We have...

  9. Large-deformation properties of wheat dough in uni- and biaxial extension. Part I. Flour dough

    NARCIS (Netherlands)

    Sliwinski, E.L.; Kolster, P.; Vliet, van T.

    2004-01-01

    Rheological and fracture properties of optimally mixed flour doughs from three wheat cultivars which perform differently in cereal products were studied in uniaxial and biaxial extension. Doughs were also tested in small angle sinusoidal oscillation. In accordance with previously published results t

  10. On the sensitivity of directions that support Voigt wave propagation in infiltrated biaxial dielectric materials

    Science.gov (United States)

    Mackay, Tom G.

    2014-01-01

    Voigt wave propagation (VWP) was considered in a porous biaxial dielectric material that was infiltrated with a material of refractive index n. The infiltrated material was regarded as a homogenized composite material in the long wavelength regime, and its constitutive parameters were estimated using the extended Bruggeman homogenization formalism. In our numerical studies, the directions that support VWP were found to vary by as much as 300 deg per RIU as the refractive index n was varied. The sensitivities achieved were acutely dependent upon the refractive index n and the degrees of anisotropy and dissipation of the porous biaxial material. The orientations, shapes, and sizes of the particles that constitute the infiltrating material and the porous biaxial material exerted only a secondary influence on the maximum sensitivities achieved. Also, for the parameter ranges considered, the degree of porosity of the biaxial material had little effect on the maximum sensitivities achieved. These numerical findings bode well for the possible harnessing of VWP for optical sensing applications.

  11. Phase diagram of colloidal spheres in a biaxial electric or magnetic field

    NARCIS (Netherlands)

    Smallenburg, F.; Dijkstra, M.

    2010-01-01

    Colloidal particles with a dielectric constant mismatch with the surrounding solvent in an external biaxial magnetic or electric field experience an “inverted” dipolar interaction. We determine the phase behavior of such a system using Helmholtz free energy calculations in Monte Carlo simulations fo

  12. 2D nonlocal versus 3D bifurcation studies for biaxially loaded plates

    DEFF Research Database (Denmark)

    Benallal, A.; Tvergaard, Viggo

    1998-01-01

    The main objective of this work is to analyse how a two-dimensional second gradient plasticity model is able to reproduce the three-dimensional bifurcation behaviour for a biaxially loaded flat plate. While it is found that the simple model used here is able to capture them qualitatively for the ...

  13. Biaxial flexural strength of Turkom-Cera core compared to two other all-ceramic systems

    Directory of Open Access Journals (Sweden)

    Bandar Mohammed Abdullah Al-Makramani

    2010-12-01

    Full Text Available Advances in all-ceramic systems have established predictable means of providing metal-free aesthetic and biocompatible materials. These materials must have sufficient strength to be a practical treatment alternative for the fabrication of crowns and fixed partial dentures. OBJECTIVES: The aim of this study was to compare the biaxial flexural strength of three core ceramic materials. MATERIAL AND METHODS: Three groups of 10 disc-shaped specimens (16 mm diameter x 1.2 mm thickness - in accordance with ISO-6872, 1995 were made from the following ceramic materials: Turkom-Cera Fused Alumina [(Turkom-Ceramic (M Sdn Bhd, Puchong, Selangor, Malaysia], In-Ceram (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany and Vitadur-N (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany, which were sintered according to the manufacturer's recommendations. The specimens were subjected to biaxial flexural strength test in an universal testing machine at a crosshead speed of 0.5 mm/min. The definitive fracture load was recorded for each specimen and the biaxial flexural strength was calculated from an equation in accordance with ISO-6872. RESULTS: The mean biaxial flexural strength values were: Turkom-Cera: 506.8±87.01 MPa, In-Ceram: 347.4±28.83 MPa and Vitadur-N: 128.7±12.72 MPa. The results were analyzed by the Levene's test and Dunnett's T3 post-hoc test (SPSS software V11.5.0 for Windows, SPSS, Chicago, IL, USA at a preset significance level of 5% because of unequal group variances (P<0.001. There was statistically significant difference between the three core ceramics (P<0.05. Turkom-Cera showed the highest biaxial flexural strength, followed by In-Ceram and Vitadur-N. CONCLUSIONS: Turkom-Cera core had significantly higher flexural strength than In-Ceram and Vitadur-N ceramic core materials.

  14. Electric field induced biaxiality and the electro-optic effect in a bent-core nematic liquid crystal

    Science.gov (United States)

    Nagaraj, Mamatha; Panarin, Y. P.; Manna, U.; Vij, J. K.; Keith, C.; Tschierske, C.

    2010-01-01

    We report the observation of a biaxial nematic phase in a bent-core molecular system using polarizing microscopy, electro-optics, and dielectric spectroscopy, where we find that the biaxiality exists on a microscopic scale. An application of electric field induces a macroscopic biaxiality and in consequence gives rise to electro-optic switching. This electro-optic effect shows significant potential in applications for displays due to its fast high-contrast response. The observed electro-optic switching is explained in terms of the interaction of the ferroelectric clusters with the electric field.

  15. Measuring knife stab penetration into skin simulant using a novel biaxial tension device.

    Science.gov (United States)

    Gilchrist, M D; Keenan, S; Curtis, M; Cassidy, M; Byrne, G; Destrade, M

    2008-05-01

    This paper describes the development and use of a biaxial measurement device to analyse the mechanics of knife stabbings. In medicolegal situations it is typical to describe the consequences of a stabbing incident in relative terms that are qualitative and descriptive without being numerically quantitative. Here, the mechanical variables involved in the possible range of knife-tissue penetration events are considered so as to determine the necessary parameters that would need to be controlled in a measurement device. These include knife geometry, in-plane mechanical stress state of skin, angle and speed of knife penetration, and underlying fascia such as muscle or cartilage. Four commonly available household knives with different geometries were used: the blade tips in all cases were single-edged, double-sided and without serrations. Appropriate synthetic materials were used to simulate the response of skin, fat and cartilage, namely polyurethane, compliant foam and ballistic soap, respectively. The force and energy applied by the blade of the knife and the out of plane displacement of the skin were all used successfully to identify the occurrence of skin penetration. The skin tension is shown to have a direct effect on both the force and energy for knife penetration and the depth of out of plane displacement of the skin simulant prior to penetration: larger levels of in-plane tension in the skin are associated with lower penetration forces, energies and displacements. Less force and energy are also required to puncture the skin when the plane of the blade is parallel to a direction of greater skin tension than when perpendicular. This is consistent with the observed behaviour when cutting biological skin: less force is required to cut parallel to the Langer lines than perpendicularly and less force is required to cut when the skin is under a greater level of tension. Finally, and perhaps somewhat surprisingly, evidence is shown to suggest that the quality control

  16. Biaxial creep behavior of ribbed GCFR cladding at 650/sup 0/C in nominally pure helium (99. 99%)

    Energy Technology Data Exchange (ETDEWEB)

    Yaggee, F. L.; Purohit, A.; Grajek, W. J.; Peoppel, R. B.

    1977-11-01

    Biaxial creep-rupture tests were conducted on 12 prototypic GCFR fuel-cladding specimens at 650/sup 0/C and a nominal hoop stress of 241.3 MPa. All test specimens were fabricated from 20% cold-worked Type 316 stainless steel tubes that were ribbed on the outer surface by mechanical grinding or electro-chemical etching. Test variables included specimen length and the presence or absence of weld-reinforcing end collars. Test results have indicated that, compared with data on smooth specimens, ribbing has no detrimental effect on creep-rupture lifetime. Specimens fabricated from tubes ribbed by electrochemical etching exhibit a significantly shorter creep-rupture lifetime and a higher secondary (steady-state) creep rate than specimens fabricated from tubes ribbed by mechanical grinding. Specimen length does not strongly affect creep-rupture lifetime, but the presence of an end collar does exhibit a significant influence on both the axial strain profile and the ratio of maximum diametral strain at the failure site to average diametral strain away from the failure site. The ribs do not inhibit the propagation of fissure or rupture failures.

  17. Monte Carlo simulations of biaxial structure in thin hybrid nematic film based upon spatially anisotropic pair potential

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhi-Dong; Chang Chun-Rui; Ma Dong-Lai

    2009-01-01

    Hybrid nematic films have been studied by Monte Carlo simulations using a lattice spin model,in which the pair potential is spatially anisotropic and dependent on elastic constants of liquid crystals.We confirm in the thin hybrid nematic film the existence of a biaxially nonbent structure and the structarc transition from the biaxial to the bent-director structure,which is similar to the result obtained using the Lebwohl-Lasher model.However,the step-like director's profile,characteristic for the biaxial structure,is spatially asymmetric in the film because the pair potential leads to K1≠K3.We estimate the upper cell thickness to be 69 spin layers,in which the biaxial structure can be found.

  18. Room temperature growth of biaxially aligned yttria-stabilized zirconia films on glass substrates by pulsed-laser deposition

    CERN Document Server

    Li Peng; Mazumder, J

    2003-01-01

    Room temperature deposition of biaxially textured yttria-stabilized zirconia (YSZ) films on amorphous glass substrates was successfully achieved by conventional pulsed-laser deposition. The influence of the surrounding gases, their pressure and the deposition time on the structure of the films was studied. A columnar growth process was revealed based on the experimental results. The grown biaxial texture appears as a kind of substrate independence, which makes it possible to fabricate in-plane aligned YSZ films on various substrates.

  19. Strength Behavior of High Strength R/C Columns under Biaxial Bending-Shear and Varying Axial Load

    OpenAIRE

    MIZOGUCHI, Mitsuo; Arakawa, Takashi; ARAI, Yasuyuki

    1991-01-01

    Twelve short square R/C columns using high-strength concrete were tested to examine the effects of biaxial bending-shear force and varying axial load on the shear and flexural strength behavior. The columns were cyclically deflected either along their transverse principal axis to produce uniaxial bending-shear or along their diagonal to produce biaxial bending-shear. For columns failing in flexure, the experimental results were found to be in close agreement with the computed values given by ...

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

    International Nuclear Information System (INIS)

    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 -1000C. 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

  1. 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.

  2. Lasing with conical diffraction feature in the KGd(WO4)2:Nd biaxial crystal

    Science.gov (United States)

    Brenier, Alain

    2016-09-01

    With an experimental set-up designed to record simultaneously the far-field and the near-field patterns, we got lasing with feature of conical diffraction in the biaxial Nd3+-doped KGd(WO4)2 crystal. The key-point is that the lasing direction is not single and is constituted by an angular distribution including the optical axis. Very slight changes of crystal orientation leads to crescent shape 1068-nm light distributions in the near-field. The beam launched towards the biaxial crystal is mainly linear polarized with its intensity in agreement with the Nd fluorescence angular distribution. A theoretical background is provided, including the monoclinic and triclinic symmetries and laser amplification including elliptical modes and cavity round trip.

  3. Tunable biaxial in-plane compressive strain in a Si nanomembrane transferred on a polyimide film

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Munho; Mi, Hongyi; Cho, Minkyu; Seo, Jung-Hun; Ma, Zhenqiang, E-mail: mazq@engr.wisc.edu [Department of Electrical and Computer Engineering, University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States); Zhou, Weidong [Department of Electrical Engineering, University of Texas at Arlington, Arlington, Texas 76019 (United States); Gong, Shaoqin [Department of Biomedical Engineering and Wisconsin Institute for Discovery, University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States)

    2015-05-25

    A method of creating tunable and programmable biaxial compressive strain in silicon nanomembranes (Si NMs) transferred onto a Kapton{sup ®} HN polyimide film has been demonstrated. The programmable biaxial compressive strain (up to 0.54%) was generated utilizing a unique thermal property exhibited by the Kapton HN film, namely, it shrinks from its original size when exposed to elevated temperatures. The correlation between the strain and the annealing temperature was carefully investigated using Raman spectroscopy and high resolution X-ray diffraction. It was found that various amounts of compressive strains can be obtained by controlling the thermal annealing temperatures. In addition, a numerical model was used to evaluate the strain distribution in the Si NM. This technique provides a viable approach to forming in-plane compressive strain in NMs and offers a practical platform for further studies in strain engineering.

  4. New classes of bi-axially symmetric solutions to four-dimensional Vasiliev higher spin gravity

    CERN Document Server

    Sundell, Per

    2016-01-01

    We present new infinite-dimensional spaces of bi-axially symmetric asymptotically anti-de Sitter solutions to four-dimensional Vasiliev higher spin gravity, obtained by modifications of the Ansatz used in arXiv:1107.1217, which gave rise to a Type-D solution space. The current Ansatz is based on internal semigroup algebras (without identity) generated by exponentials formed out of the bi-axial symmetry generators. After having switched on the vacuum gauge function, the resulting generalized Weyl tensor is given by the sum of two generalized Petrov type-D tensors, and the twistor space connections are smooth in twistor space over finite regions of spacetime. We provide evidence for that the linearized twistor space connection can be brought to Vasiliev gauge.

  5. Genuine effectively biaxial left-handed metamaterials due to extreme coupling.

    Science.gov (United States)

    Menzel, Christoph; Alaee, Rasoul; Pshenay-Severin, Ekaterina; Helgert, Christian; Chipouline, Arkadi; Rockstuhl, Carsten; Pertsch, Thomas; Lederer, Falk

    2012-02-15

    Most left-handed metamaterials cannot be described by local effective permittivity or permeability tensors in the visible or near-infrared due to the mesoscopic size of the respective unit cells and the related strong spatial dispersion. We lift this problem and propose a metamaterial exhibiting artificial magnetism that does not suffer from this restriction. The artificial magnetism arises from the extreme coupling between both metallic films forming the unit cell. We show that its electromagnetic response can be properly described by biaxial local constitutive relations. A genuine biaxial left-handed fishnet metamaterial is suggested, which can be realized by atomic layer deposition to fabricate the nanoscaled spacing layers required for extreme coupling.

  6. Cyclic plasticity of an austenitic-ferritic stainless steel under biaxial non proportional loading; Plasticite cyclique d'un acier inoxydable austeno-ferritique sous chargement biaxial non-proportionnel

    Energy Technology Data Exchange (ETDEWEB)

    Aubin, V

    2001-11-15

    Austenitic-ferritic stainless steels are supplied since about 30 years only, so they are yet not well-known. Their behaviour in cyclic plasticity was studied under uniaxial loading but not under multiaxial loading, whereas only a thorough knowledge of the phenomena influencing the mechanical behaviour of a material enables to simulate and predict accurately its behaviour in a structure. This work aims to study and model the behaviour of a duplex stainless steel under cyclic biaxial loading. A three step method was adopted. A set of tension-torsion tests on tubular specimen was first defined. We studied the equivalence between loading directions, and then the influence of loading path and loading history on the stress response of the material. Results showed that duplex stainless steel shows an extra-hardening under non proportional loading and that its behaviour depends on previous loading. Then, in order to analyse the results obtained during this first experimental stage, the yield surface was measured at different times during cyclic loading of the same kind. A very small plastic strain offset (2*10{sup -5}) was used in order not to disturb the yield surface measured. The alteration of isotropic and kinematic hardening variables were deduced from these measures. Finally, three phenomenological constitutive laws were identified with the experimental set. We focused our interest on the simulation of stabilized stress levels and on the simulation of the cyclic hardening/softening behaviour. The comparison between experimental and numerical results enabled the testing of the relevance of these models. (authors)

  7. A twist-bend nematic to an intercalated, anticlinic, biaxial phase transition in liquid crystal bimesogens.

    Science.gov (United States)

    Mandle, Richard J; Goodby, John W

    2016-02-01

    In this article we describe for bimesogens the first observed transition from a "heliconical" twist-bend nematic liquid crystal to a novel biaxial, anticlinic, intercalated lamellar phase. The phase behaviour and structures of both polymorphs is similar to that of polymers, confirming that bimesogens can act as model systems for main chain liquid crystal polymers, and in principle are separate soft-matter branches of self-organising systems. PMID:26626825

  8. Non-proportional tension-shear experiments in a biaxial test facility

    OpenAIRE

    Riel, van, A.C.M.J.; Boogaard, van den, F.E.; Huetink, J.

    2006-01-01

    This paper discusses the results obtained from experiments on DC06 mild steel with a biaxial test facility. The two presented tests are non-proportional tests consisting of a two stage strain path. First the samples are deformed in the tensile direction after which simple shear deformation is applied. In the one case elastic unloading is applied after the tensile deformation, while in the other case the tensile deformation is directly followed by the simple shear deformation. For the test wit...

  9. Measuring knife stab penetration into skin simulant using a novel biaxial tension device

    OpenAIRE

    Gilchrist, M. D.; Keenan, S.; Curtis, Michael; et al.,

    2008-01-01

    This paper describes the development and use of a biaxial measurement device to analyse the mechanics of knife stabbings. In medicolegal situations it is typical to describe the consequences of a stabbing incident in relative terms that are qualitative and descriptive without being numerically quantitative. Here, the mechanical variables involved in the possible range of knife-tissue penetration events are considered so as to determine the necessary parameters that would need to be controlled...

  10. Characterization of biaxial mechanical behavior of porcine aorta under gradual elastin degradation

    OpenAIRE

    Zeinali-Davarani, Shahrokh; Chow, Ming-Jay; Turcotte, Raphaël; Zhang, Yanhang

    2013-01-01

    Arteries are composed of multiple constituents that endow the wall with proper structure and function. Many vascular diseases are associated with prominent mechanical and biological alterations in the wall constituents. In this study, planar biaxial tensile test data of elastase-treated porcine aortic tissue (Chow et al. 2012) is re-examined to characterize the altered mechanical behavior at multiple stages of digestion through constitutive modeling. Exponential-based as well as recruitment-b...

  11. Novel biaxial tensile test for studying aortic failure phenomena at a microscopic level

    Directory of Open Access Journals (Sweden)

    Sugita Shukei

    2013-01-01

    Full Text Available Abstract Background An aortic aneurysm is a local dilation of the aorta, which tends to expand and often results in a fatal rupture. Although larger aneurysms have a greater risk of rupture, some small aneurysms also rupture. Since the mechanism of aortic rupture is not well understood, clarification of the microstructure influencing the failure to rupture is important. Since aortic tissues are stretched biaxially in vivo, we developed a technique to microscopically observe the failure of an aortic rupture during biaxial stretch. Methods A thinly sliced porcine thoracic aortic specimen was adhered to a circular frame and pushed onto a cylinder with a smaller diameter to stretch the specimen biaxially. To induce failure to rupture at the center, the specimen was thinned at the center of the hole as follows: the specimen was frozen while being compressed with metal plates having holes, which were 3 mm in diameter at their centers; the specimen was then sliced at 50-μm intervals and thawed. Results The ratio of the thickness at the center to the peripheral area was 99.5% for uncompressed specimens. The ratio decreased with an increase in the compression ratio εc and was 47.3% for specimens with εc = 40%. All specimens could be stretched until failure to rupture. The probability for crack initiation within the cylinder was εc εc >30%, respectively. Among specimens ruptured within the cylinder, 93% of those obtained from the mid-media showed crack initiation at the thin center area. Conclusions Aortic tissues were successfully stretched biaxially until failure, and their crack initiation points were successfully observed under a microscope. This could be a very useful and powerful method for clarifying the mechanism of aortic rupture. We are planning to use this technique for a detailed investigation of events occurring at the point of failure when the crack initiates in the aortic aneurysm wall.

  12. Fracture Propagation Characteristic and Micromechanism of Rock-Like Specimens under Uniaxial and Biaxial Compression

    OpenAIRE

    Xue-wei Liu; Quan-sheng Liu; Shi-bing Huang; Lai Wei; Guang-feng Lei

    2016-01-01

    This paper presents a set of uniaxial and biaxial compression tests on the rock-like material specimens with different fracture geometries through a rock mechanics servo-controlled testing system (RMT-150C). On the basis of experimental results, the characteristics of fracture propagation under different fracture geometries and loading conditions are firstly obtained. The newly formed fractures are observed propagating from or near the preexisting crack tips for different specimens, while the...

  13. Biaxial Texture Evolution in MgO Films Fabricated Using Ion Beam-Assisted Deposition

    Science.gov (United States)

    Xue, Yan; Zhang, Ya-Hui; Zhao, Rui-Peng; Zhang, Fei; Lu, Yu-Ming; Cai, Chuan-Bing; Xiong, Jie; Tao, Bo-Wan

    2016-07-01

    The growth of multifunctional thin films on flexible substrates is important technologically, because flexible electronics require such a platform. In this study, we examined the evolution of biaxial texture in MgO films prepared using ion beam-assisted deposition (IBAD) on a Hastelloy substrate. Texture and microstructure developments were characterized through in situ reflection high-energy electron diffraction monitoring, x-ray diffraction, and atomic force microscopy, which demonstrated that biaxial texture was developed during the nucleation stage (~2.2 nm). The best biaxial texture was obtained with a thickness of approximately 12 nm. As MgO continued to grow, the influence of surface energy was reduced, and film growth was driven by the attempt to minimize volume free-energy density. Thus the MgO grains were subsequently rotated at the (002) direction toward the ion beam. In addition, an approach was developed for accelerating in-plane texture evolution by pre-depositing an amorphous MgO layer before IBAD.

  14. Biaxial CdTe/CaF{sub 2} films growth on amorphous surface

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, W., E-mail: yuanw@rpi.ed [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Tang, F.; Li, H.-F.; Parker, T. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); LiCausi, N. [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Lu, T.-M. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Bhat, I. [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Wang, G.-C. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110, 8th St., Troy, NY 12180 (United States); Lee, S. [US Army Armament Research, Development and Engineering Center, Benet Labs, Watervliet, NY 12189 (United States)

    2009-10-30

    A continuous and highly biaxially textured CdTe film was grown by metal organic chemical vapor deposition on an amorphous substrate using biaxial CaF{sub 2} nanorods as a buffer layer. The interface between the CdTe film and CaF{sub 2} nanorods and the morphology of the CdTe film were studied by transmission electron microscopy (TEM) and scanning electron microscopy. Both the TEM and X-ray pole figure analysis clearly reveal that the crystalline orientation of the continuous CdTe film followed the {l_brace}111{r_brace}<121> biaxial texture of the CaF{sub 2} nanorods. A high density of twin faults was observed in the CdTe film. Furthermore, the near surface texture of the CdTe thin film was investigated by reflection high-energy electron diffraction (RHEED) and RHEED surface pole figure analysis. Twinning was also observed from the RHEED surface pole figure analysis.

  15. Fabrication and reliable implementation of an ionic polymer-metal composite (IPMC) biaxial bending actuator

    Science.gov (United States)

    Lee, Gil-Yong; Choi, Jung-Oh; Kim, Myeungseon; Ahn, Sung-Hoon

    2011-10-01

    Ionic polymer-metal composites (IPMCs) are one of the most popular types of electro-active polymer actuator, due to their low electric driving potential, large deformation range, and light weight. IPMCs have been used as actuators or sensors in many areas of biomedical and robotic engineering. In this research, IPMCs were studied as a biaxial bending actuator capable of smart and flexible motion. We designed and fabricated this bending actuator and implemented it to have a reliable actuating motion using a systematic approach. The resulting device was bar shaped with a square cross section and had four insulated electrodes on its surface. By applying different voltages to these four electrodes, a biaxial bending motion can be induced. To construct this actuator, several fabrication processes were considered. We modified the Nafion stacking method, and established a complete sequence of actuator fabrication processes. Using these processes, we were able to fabricate an IPMC biaxial bending actuator with both high actuating force and high flexibility. Several experiments were conducted to investigate and verify the performance of the actuator. The IPMC actuator system was modeled from experimentally measured data, and using this actuator model, a closed-loop proportional integral (PI) controller was designed. Reference position tracking performances of open-loop and closed-loop systems were compared. Finally, circular motion tracking performances of the actuator tip were tested under different rotation frequencies and radii of a reference trajectory circle.

  16. Loading system mechanism for dielectric elastomer generators with equi-biaxial state of deformation

    Science.gov (United States)

    Fontana, M.; Moretti, G.; Lenzo, B.; Vertechy, R.

    2014-03-01

    Dielectric Elastomer Generators (DEGs) are devices that employ a cyclically variable membrane capacitor to produce electricity from oscillating sources of mechanical energy. Capacitance variation is obtained thanks to the use of dielectric and conductive layers that can undergo different states of deformation including: uniform or non-uniform and uni- or multi-axial stretching. Among them, uniform equi-biaxial stretching is reputed as being the most effective state of deformation that maximizes the amount of energy that can be extracted in a cycle by a unit volume of Dielectric Elastomer (DE) material. This paper presents a DEG concept, with linear input motion and tunable impedance, that is based on a mechanical loading system for inducing uniform equi-biaxial states of deformation. The presented system employs two circular DE membrane capacitors that are arranged in an agonist-antagonist configuration. An analytical model of the overall system is developed and used to find the optimal design parameters that make it possible to tune the elastic response of the generator over the range of motion of interest. An apparatus is developed for the equi-biaxial testing of DE membranes and used for the experimental verification of the employed numerical models.

  17. Flexural strength of dental composite restoratives: comparison of biaxial and three-point bending test.

    Science.gov (United States)

    Chung, S M; Yap, A U J; Chandra, S P; Lim, C T

    2004-11-15

    This study compared two test methods used to evaluate the flexural strength of resin-based dental composites. The two test methods evaluated were the three-point bending test4 and the biaxial flexural test. Materials used in this investigation were from the same manufacturer (3M ESPE) and included microfill (A110), minifill (Z100 and Filtek Z250), polyacid modified (F2000), and flowable [Filtek Flowable (FF)] composites. Flexural strength was determined with the use of both test methods after 1 week of conditioning in water at 37 degrees C. Data were analyzed with the use of an ANOVA/Scheffe test and an independent-samples t test at significance level 0.05. Mean flexural strength (n = 7) ranged from 66.61 to 147.21 and 67.27 to 182.81 MPa for three-point bending and ball-on-three-ball biaxial test methods, respectively. In both test methods, Z100 was significantly stronger than all other composites evaluated. In the three-point bending test, flexural strength of Z250 was significantly higher than A110, F2000 and FF, and FF was significantly stronger than A110 and F2000. The biaxial test method arrived at the same conclusions except that there was no significant difference between Z250 and FF. Pearson's correlation revealed a significantly (p bending test. PMID:15386492

  18. Instability of a Biaxial Nematic Liquid Crystal Formed by Homeotropic Anchoring on Surface Grooves

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Dong; XUAN Li

    2011-01-01

    A method used to treat the elastic distortion of a uniaxial nematic liquid crystal induced by homogeneous anchoring on the surface grooves is generalized to biaxial nematic liquid crystals under the homeotropic anchoring condition.Employing some approximations for the elastic constants,we obtain an additional term in the elastic energy per unit area which depends on the angle between the minor director at infinity and the direction of the grooves,with a period of π/2.This leads to instability on the surface grooves so that two states with crossed minor directors are energetically indistinguishable.Our theoretical study explains why the homeotropic alignment method developed for uniaxial liquid crystals loses efficacy for biaxial nematics.In most liquid crystal devices,the liquid crystals are sandwiched between two substrates coated with alignment layers.In the absence of externally applied fields,the orientation of the liquid crystal in the cell is determined by the anchoring condition of the alignment layer.[1-3] One usually distinguishes three main types of liquid crystalline director alignment near solid walls:homeotropic,homogeneous (or planar) and tilted orientations.Here we study the first of these and consider the biaxial nematic phase,which was observed in lyotropic systems as early as 1980[4] and has been confirmed by deuterium NMR spectroscopy.%A method used to treat the elastic distortion of a uniaxial nematic liquid crystal induced by homogeneous anchoring on the surface grooves is generalized to biaxial nematic liquid crystals under the homeotropic anchoring condition. Employing some approximations for the elastic constants, we obtain an additional term in the elastic energy per unit area which depends on the angle between the minor director at infinity and the direction of the grooves, with a period of π/2. This leads to instability on the surface grooves so that two states with crossed minor directors are energetically indistinguishable. Our

  19. In situ biaxial texture analysis of MGO films during growth on amorphous substrates by ion beam-assisted deposition

    Energy Technology Data Exchange (ETDEWEB)

    Brewer, R. T. (Rhett T.); Arendt, P. N. (Paul N.); Atwater, H. A. (Harry A.); Groves, J. R. (James R.)

    2001-01-01

    We used a previously reported kinematical electron scattering model to develop a RHEED based method for performing quantitative analysis of mosaic polycrystalline thin film in-plane and out-of-plain grain orientation distributions. RHEED based biaxial texture measurements are compared to X-Ray and transmission electron microscopy measurements to establish the validity of the RHEED analysis method. In situ RHEED analysis reveals that the out of plane orientation distribution starts out very broad, and then decreases during IBAD MgO growth. Other results included evidence that the in-plane orientation distribution narrows, the grain size increases, and the film roughens as film thickness increases during IBAD MgO growth. Homoepitaxy of MgO improves the biaxial texture of the IBAD layer, making X-ray measurements of IBAD films with an additional homoepitaxial layer not quantitatively representative of the IBAD layer. Systematic offsets between RHEED analysis and X-ray measurements of biaxial texture, coupled with evidence that biaxial texture improves with increasing film thickness, indicate that RHEED is a superior technique for probing surface biaxial texture.

  20. Study of the effect of an equi-biaxial loading on the fatigue lifetime of austenitic stainless steel

    International Nuclear Information System (INIS)

    Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures.In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equi-biaxial tension. The aim of this study is to present the experimental and numerical results obtained with a device 'FABIME2' developed in the LISN in collaboration with EDF and AREVA. The association of the experimental results, obtained on the new experimental fatigue device FABIME2, with the numerical analyses obtained by FEM simulation with Cast3M code, has enabled to define the aggravating effect of the equi-biaxial fatigue loading. However, this effect is covered by the Design fatigue curve defined from the nuclear industry. For the crack propagation, a first simplified approach enables to study the kinetic behavior of crack propagation in equi-biaxial fatigue. (author)

  1. Ductile Tearing of Thin Aluminum Plates Under Blast Loading. Predictions with Fully Coupled Models and Biaxial Material Response Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Corona, Edmundo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gullerud, Arne S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Haulenbeek, Kimberly K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Reu, Phillip L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-06-01

    The work presented in this report concerns the response and failure of thin 2024- T3 aluminum alloy circular plates to a blast load produced by the detonation of a nearby spherical charge. The plates were fully clamped around the circumference and the explosive charge was located centrally with respect to the plate. The principal objective was to conduct a numerical model validation study by comparing the results of predictions to experimental measurements of plate deformation and failure for charges with masses in the vicinity of the threshold between no tearing and tearing of the plates. Stereo digital image correlation data was acquired for all tests to measure the deflection and strains in the plates. The size of the virtual strain gage in the measurements, however, was relatively large, so the strain measurements have to be interpreted accordingly as lower bounds of the actual strains in the plate and of the severity of the strain gradients. A fully coupled interaction model between the blast and the deflection of the structure was considered. The results of the validation exercise indicated that the model predicted the deflection of the plates reasonably accurately as well as the distribution of strain on the plate. The estimation of the threshold charge based on a critical value of equivalent plastic strain measured in a bulge test, however, was not accurate. This in spite of efforts to determine the failure strain of the aluminum sheet under biaxial stress conditions. Further work is needed to be able to predict plate tearing with some degree of confidence. Given the current technology, at least one test under the actual blast conditions where the plate tears is needed to calibrate the value of equivalent plastic strain when failure occurs in the numerical model. Once that has been determined, the question of the explosive mass value at the threshold could be addressed with more confidence.

  2. Application of Bi-axial Warp Knitted Structures in Concrete Constructions

    Institute of Scientific and Technical Information of China (English)

    李炜; 陈南梁

    2001-01-01

    The warp knitted bi-axial directionally oriented structure (D. O. S. ) reinforcement substrates applied to building construction are discussed in comparison to woven fabrics. One of usage barriers of reinforced cement with gloss-grid is its sensitivity to alkali existed in the cement which will lead to the reduction of its service-life. The tests show that the treatment by sol-gel method to protect the composite from alkali corrosion is effective. Then two formulae of sol-gel solution are also recommended here for application.

  3. Collinear Acousto-Optical Transformation of Bessel Light Beams in Biaxial Gyrotropic Crystals

    Science.gov (United States)

    Belyi, V. N.; Kulak, G. V.; Krokh, G. V.; Shakin, O. V.

    2016-05-01

    The collinear acousto-optical transformation of Bessel light beams in biaxial gyrotropic crystals into two annular, internal conical refraction beams with orthogonal elliptical polarization is studied. It is found that the diffraction efficiency is maximal (~50-60%) for low ultrasound intensities and varies slightly with further increases in acoustic power. At high ultrasound intensities, the intensities of the transmitted and diffracted annular beams differ insignificantly. The possible use of this acousto-optical interaction for creating collinear tuneable narrow-band acousto-optical filters at low ultrasonic frequencies is demonstrated.

  4. Biaxially stretchable supercapacitors based on the buckled hybrid fiber electrode array

    Science.gov (United States)

    Zhang, Nan; Zhou, Weiya; Zhang, Qiang; Luan, Pingshan; Cai, Le; Yang, Feng; Zhang, Xiao; Fan, Qingxia; Zhou, Wenbin; Xiao, Zhuojian; Gu, Xiaogang; Chen, Huiliang; Li, Kewei; Xiao, Shiqi; Wang, Yanchun; Liu, Huaping; Xie, Sishen

    2015-07-01

    In order to meet the growing need for smart bionic devices and epidermal electronic systems, biaxial stretchability is essential for energy storage units. Based on porous single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) (SWCNT/PEDOT) hybrid fiber, we designed and fabricated a biaxially stretchable supercapacitor, which possesses a unique configuration of the parallel buckled hybrid fiber array. Owing to the reticulate SWCNT film and the improved fabrication technique, the hybrid fiber retained its porous architecture both outwardly and inwardly, manifesting a superior capacity of 215 F g-1. H3PO4-polyvinyl alcohol gel with an optimized component ratio was introduced as both binder and stretchable electrolyte, which contributed to the regularity and stability of the buckled fiber array. The buckled structure and the quasi one-dimensional character of the fibers endow the supercapacitor with 100% stretchability along all directions. In addition, the supercapacitor exhibited good transparency, as well as excellent electrochemical properties and stability after being stretched 5000 times.In order to meet the growing need for smart bionic devices and epidermal electronic systems, biaxial stretchability is essential for energy storage units. Based on porous single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) (SWCNT/PEDOT) hybrid fiber, we designed and fabricated a biaxially stretchable supercapacitor, which possesses a unique configuration of the parallel buckled hybrid fiber array. Owing to the reticulate SWCNT film and the improved fabrication technique, the hybrid fiber retained its porous architecture both outwardly and inwardly, manifesting a superior capacity of 215 F g-1. H3PO4-polyvinyl alcohol gel with an optimized component ratio was introduced as both binder and stretchable electrolyte, which contributed to the regularity and stability of the buckled fiber array. The buckled structure and the quasi one-dimensional character of the

  5. Biaxial high cycle fatigue: experimental investigation and two-scale damage model

    International Nuclear Information System (INIS)

    This research thesis first describes the multi-axial fatigue phenomenon in the cases of mechanical and complex loadings, discusses multi-axial fatigue criteria, and presents the approach of fatigue by incremental damage mechanics. Then, it reports an experimental investigation of fatigue crack initiation under biaxial polycyclic fatigue in 304L austenitic stainless steel and in titanium alloy. The author presents a probabilistic two-scale damage model, and then reports the assessment of multi-axial fatigue life by means of this model

  6. Control of biaxial strain in single-layer Molybdenite using local thermal expansion of the substrate

    OpenAIRE

    Plechinger, G.; Castellanos-Gomez, A.; Buscema, M.; van der Zant, H. S. J.; Steele, G. A.; Kuc, A.; Heine, T.; Schüller, C; Korn, T.

    2015-01-01

    Single-layer MoS2 is a direct-gap semiconductor whose electronic band structure strongly depends on the strain applied to its crystal lattice. While uniaxial strain can be easily applied in a controlled way, e.g., by bending of a flexible substrate with the atomically thin MoS2 layer on top, experimental realization of biaxial strain is more challenging. Here, we exploit the large mismatch between the thermal expansion coefficients of MoS2 and a silicone-based substrate to apply a controllabl...

  7. Transformation of vector beams with radial and azimuthal polarizations in biaxial crystals

    CERN Document Server

    Turpin, Alex; Lizana, Angel; Torres-Ruiz, Fabián; Estévez, Irene; Moreno, Ignacio; Campos, Juan; Mompart, Jordi

    2015-01-01

    We present both experimentally and theoretically the transformation of radially and azimuthally polarized vector beams when they propagate through a biaxial crystal and are transformed by the conical refraction phenomenon. We show that, at the focal plane, the transverse pattern is formed by a ring-like light structure with an azimuthal node, being this node found at diametrically opposite points of the ring for radial/azimuthal polarizations. We also prove that the state of polarization of the transformed beams is conical refraction-like, i.e. that every two diametrically opposite points of the light ring are linearly orthogonally polarized.

  8. Electronic and optical properties of kesterite Cu{sub 2}ZnSnS{sub 4} under in-plane biaxial strains: First-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chun-Ran [State Key Laboratory of Superhard Materials and College of Physics, Jilin University, Changchun 130012 (China); College of Mathematics and Physics, Bohai University, Jinzhou 121013 (China); Li, Yong-Feng, E-mail: liyongfeng@jlu.edu.cn [State Key Laboratory of Superhard Materials and College of Physics, Jilin University, Changchun 130012 (China); Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Yao, Bin, E-mail: binyao@jlu.edu.cn [State Key Laboratory of Superhard Materials and College of Physics, Jilin University, Changchun 130012 (China); Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Yang, Gang [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Ding, Zhan-Hui [State Key Laboratory of Superhard Materials and College of Physics, Jilin University, Changchun 130012 (China); Deng, Rui [School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022 (China); Liu, Lei [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, No. 3888 Dongnanhu Road, Changchun 130033 (China)

    2013-11-08

    The electronic structures and optical properties of Cu{sub 2}ZnSnS{sub 4} (CZTS) under in-plane biaxial strain were systematically investigated using first-principles calculations based on generalized gradient approximation and hybrid functional method, respectively. It is found that the fundamental bandgap at the Γ point decreases linearly with increasing tensile biaxial strain perpendicular to c-axis. However, a bandgap maximum occurs as the compressive biaxial strain is 1.5%. Further increase of compressive strain decreases the bandgap. In addition, the optical properties of CZTS under biaxial strain are also calculated, and the variation trend of optical bandgap with biaxial strain is consistent with the fundamental bandgap.

  9. Effects of the biaxial transverse crystal-field on the phase diagrams of a spin-1 nanowire

    Science.gov (United States)

    Magoussi, H.; Zaim, A.; Boughrara, M.; Kerouad, M.

    2016-09-01

    By using the effective field theory based on a probability distribution method, the phase diagrams and the magnetic properties of an Ising nanowire in the presence of the biaxial transverse crystal-field are investigated. The effects of the biaxial transverse crystal field, the interfacial coupling and the exchange interaction in the surface on the phase diagram, the magnetization and the internal energy are examined. Some characteristic phenomena are found such as the tricritical behavior, the critical end point and the re-entrant phenomenon.

  10. Biaxial-Type Concentrated Solar Tracking System with a Fresnel Lens for Solar-Thermal Applications

    Directory of Open Access Journals (Sweden)

    Tsung Chieh Cheng

    2016-04-01

    Full Text Available In this paper, an electromechanical, biaxial-type concentrated solar tracking system was designed for solar-thermal applications. In our tracking system, the sunlight was concentrated by the microstructure of Fresnel lens to the heating head of the Stirling engine and two solar cells were installed to provide the power for tracking system operation. In order to obtain the maximum sun power, the tracking system traces the sun with the altitude-azimuth biaxial tracing method and accurately maintains the sun’s radiation perpendicular to the plane of the heating head. The results indicated that the position of heating head is an important factor for power collection. If the sunlight can be concentrated to completely cover the heating head with small heat loss, we can obtain the maximum temperature of the heating head of the Stirling engine. Therefore, the temperature of heating head can be higher than 1000 °C in our experiment on a sunny day. Moreover, the results also revealed that the temperature decrease of the heating head is less than the power decrease of solar irradiation because of the latent heat of copper and the small heat loss from the heating head.

  11. Fracture Propagation Characteristic and Micromechanism of Rock-Like Specimens under Uniaxial and Biaxial Compression

    Directory of Open Access Journals (Sweden)

    Xue-wei Liu

    2016-01-01

    Full Text Available This paper presents a set of uniaxial and biaxial compression tests on the rock-like material specimens with different fracture geometries through a rock mechanics servo-controlled testing system (RMT-150C. On the basis of experimental results, the characteristics of fracture propagation under different fracture geometries and loading conditions are firstly obtained. The newly formed fractures are observed propagating from or near the preexisting crack tips for different specimens, while the propagation paths are affected by the loading condition obviously. Then, by adopting acoustic emission (AE location technique, AE event localization characteristics in the process of loading are investigated. The locations of AE events are in good agreement with the macroscopic fracture propagation path. Finally, the micromechanism of macroscopic fracture propagation under uniaxial and biaxial compression conditions is analyzed, and the fracture propagation can be concluded as a result of microdamage accumulation inside the material. The results of this paper are helpful for theory and engineering design of the fractured rock mass.

  12. Effects of Arbitrarily Directed Field on Spin Phase Oscillations in Biaxial Molecular Magnets

    Institute of Scientific and Technical Information of China (English)

    HU Hui; ZHU JiaLin; LU Rong; XIONG JiaJiong

    2001-01-01

    Quantum phase interference and spin-parity effects are studied in biaxial molecular magnets in a magnetic field at an arbitrarily directed angle. The calculations of the ground-state tunnel splitting are performed on the basis of the instanton technique in the spin-coherent-state path-integral representation, and complemented by exactly numerical diagonalization. Both the Wentzel-Kramers-Brillouin exponent and the pre-exponential factor are obtained for the entire region of the direction of the field. Our results show that the tunnel splitting oscillates with the field for the small field angle, while for the large field angle the oscillation is completely suppressed. This distinct angular dependence, together with the dependence of the tunnel splitting on the field strength, provides an independent test for spin-parity effects in biaxial molecular magnets. The analytical results for the molecular Fes magnet are found to be in good agreement with the numerical simulations, which suggests that even the molecular magnet with total spin S = 10 is large enough to be treated as a giant spin system.``

  13. Upregulation of matrix synthesis in chondrocyte-seeded agarose following sustained bi-axial cyclic loading

    Directory of Open Access Journals (Sweden)

    Belinda Pingguan-Murphy

    2012-08-01

    Full Text Available OBJECTIVES: The promotion of extracellular matrix synthesis by chondrocytes is a requisite part of an effective cartilage tissue engineering strategy. The aim of this in vitro study was to determine the effect of bi-axial cyclic mechanical loading on cell proliferation and the synthesis of glycosaminoglycans by chondrocytes in threedimensional cultures. METHOD: A strain comprising 10% direct compression and 1% compressive shear was applied to bovine chondrocytes seeded in an agarose gel during two 12-hour conditioning periods separated by a 12-hour resting period. RESULTS: The bi-axial-loaded chondrocytes demonstrated a significant increase in glycosaminoglycan synthesis compared with samples exposed to uni-axial or no loading over the same period (p<0.05. The use of a free-swelling recovery period prior to the loading regime resulted in additional glycosaminoglycan production and a significant increase in DNA content (p<0.05, indicating cell proliferation. CONCLUSIONS: These results demonstrate that the use of a bi-axial loading regime results in increased matrix production compared with uni-axial loading.

  14. Characterization of Biaxial and Triaxial Braids: Fiber Architecture and Mechanical Properties

    Science.gov (United States)

    Birkefeld, Karin; Röder, Mirko; von Reden, Tjark; Bulat, Martina; Drechsler, Klaus

    2012-06-01

    Biaxial and triaxial carbon fiber braids with off-axis braiding angles of 30°, 45° and 55° are characterized with respect to their fiber architecture. All braids are produced on a round mandrel with constant cross section. Detailed geometric information on the different braids, like roving dimensions, roving shapes and the degree of nesting is given. The findings from measurements in photomicrographs are used to construct meso-model yarn architectures at the unit cell level which are then analyzed with the WiseTex software (Lomov et al. Compos. Sci. Technol. 60:2083-2095, 2000). The results of the models' analysis with TexComp and comparison of mechanical properties with tests are consistent and essential for further steps in predictive modeling. Predictive modeling was also performed for biaxial braids based on the packing density in the material and parameters of the braiding process. The good conformance of the predictive models gives a validated starting point for development of braided structures concerning stiffness behavior. In addition, the information about the fiber architecture can be used for failure analysis on unit cell level.

  15. Practical approach in surface modification of biaxially oriented polypropylene films for gravure printability

    Science.gov (United States)

    Nuntapichedkul, Boonchai; Tantayanon, Supawan; Laohhasurayotin, Kritapas

    2014-09-01

    Biaxially oriented polypropylene (BOPP) film is one of the most popularly used materials for the gravure printing process in flexible packaging industry. The skin layers of BOPP film were associated with 3-6 weight % of propylene-ethylene copolymer. These films were completely biaxial-oriented by sequential stretching process after which the film surfaces were subjected to corona treatment integrated in the production line. The FT-IR results exhibited that polar functional groups as carbonyl molecules were established on the corona-treated BOPP film. The contact angles of these BOPP films were measured; the surface free energies (SFE) were then calculated. AFM topographical images also agreed well with the SFE which increased as the contents of propylene-ethylene copolymer increased. An approximated 20% increased SFE was obtained for the BOPP film that was associated with 6% propylene-ethylene copolymer. The printing quality on BOPP films was tested by light microscope which confirmed that the chromatic resolution of the printed images improved down to even more smaller groove sizes, 10 or 5 dot%. This improvement was also examined and found to correspond well with the interfacial tensions and work of adhesion between the inks and the modified BOPP films.

  16. 堆石坝防渗土工膜薄壁圆筒双向拉伸性能测试方法%Thin-Walled Cylinder Biaxial Tensile Test Method of Waterproof Geomembrane for Rockfill Dams

    Institute of Scientific and Technical Information of China (English)

    任泽栋; 姜晓桢; 满晓磊; 蒋善平; 乌景秀

    2013-01-01

    Tensile properties of waterproof geomembrane for rockfill dams play an important role in resistance of changing external loads.A discussion has been made about the standard test method for tensile properties in the specification of the geomembranes.At the same time,various research achievements at home and abroad,which are related to this,have been analyzed and compared.Based on the discussion above,a new biaxial tension test method is developed for loading a thin-walled cylinder specimen.Finally,a comparison about the various methods for tensile properties of geomembrane has been made in detail at the angle of mechanical properties by using the linear elastic model of the finite element software,which is under the condition of the same displacement load.The numerical simulation results show that the thin-walled cylinder biaxial tensile test can accurately reflect the mechanical properties of geomembrane under biaxial tensile test.In addition,the stress obtained by this new mechanism are more uniform than the existing mullen test and the cruciform biaxial tensile test,which shows a better test effects.%由于堆石坝防渗用土工膜拉伸性能在抵抗外部荷载变化中发挥重要作用,文章对规范中的土工膜拉伸性能测试方法以及国内外有关研究成果进行对比分析,并在此基础上提出了薄壁圆筒双向拉伸测试方法,最后,利用有限元软件中的线弹性模型对相同位移荷载条件下的各种试验方法进行数值模拟.结果表明:薄壁圆筒双向拉伸试验能够准确反应土工膜在双向拉伸条件下的力学特性;与现有的液胀试验和十字形双向拉伸试验相比,薄壁圆筒试样应力分布更加均匀,试验效果更优.

  17. Biaxial flexural strength of high-viscosity glass-ionomer cements heat-cured with an LED lamp during setting

    NARCIS (Netherlands)

    Molina, G. Fabian; Cabral, R.J.; Mazzola, I.; Lascano, L. Brain; Frencken, J.E.F.M.

    2013-01-01

    Adding heat to glass ionomers during setting might improve mechanical properties. The aim was to compare the biaxial flexural strength (BFS) between and within four glass ionomers, by time of exposure to a high-intensity LED light-curing unit. Materials and methods. Samples of Fuji 9 Gold Label, Ket

  18. Growth of Biaxially Textured Yttria-Stabilized Zirconia Thin Films on Si(111) Substrate by Ion Beam Assisted Deposition

    Institute of Scientific and Technical Information of China (English)

    MU Hai-Chuan; REN Cong-Xin; JIANG Bing-Yao; DING Xing-Zhao; YU Yue-Hui; WANG Xi; LIU Xiang-Huai; ZHOU Gui-En; JIA Yun-Bo

    2000-01-01

    The (001) oriented yttria-stabilized zirconia (YSZ) films with in-plane biaxial texture have been deposited on Si(lll ) substrates by ion beam assisted deposition at ambient temperature. The effects of ion/atom arrival rate ratio (R=(Ar+ +O2+)/ZrO2) and incident angle of bombarding ion beam on the film texture development were investigated. It was found that the in-plane biaxial texture of the films was improved gradually with increasing ion/atom arrival rate ratio R up to a critical value 1.9, but it was degraded with the further increase of R. The optimal in-plane biaxial texture, whose full width at half maximum of the (lll) φ-scan spectrum is 14°, can be obtained at R=1.9 and incident angle of 55°. For a fixed R, the optimal crystallinity and in-plane biaxial alignment of the YSZ films did not appear at the same incident angle and showed an opposite variation with the change of the incident angle from 51° to 55°. C-axis lignment (perpendicular to substrate surface) does not show any substantial variation with the change of incident angle within the range of 47° - 56°.

  19. Residual stress in nano-structured stainless steel (AISI 316L) prompted by Xe+ ion bombardment at different impinging angles

    Science.gov (United States)

    Cucatti, S.; Droppa, R.; Figueroa, C. A.; Klaus, M.; Genzel, Ch.; Alvarez, F.

    2016-10-01

    The effect of low energy (Plot" methods. The analysis shows the absence of shear stress in the affected material region and the presence of compressive in-plane residual biaxial stress (˜200 MPa) expanding up to ˜1 μm depth for all the studied samples. Samples under oblique bombardment present higher compressive stress values in the direction of the projected ion beam on the bombarded surface. The absolute value of the biaxial surface stress difference (σ11-σ22) increases on ion impinging angles, a phenomenon associated with the momentum transfer by the ions. The highest stress level was measured for ion impinging angles of 45° ( σ 11 = -380 ± 10 MPa and σ 22 = -320 ± 10 MPa). The different stresses obtained in the studied samples do not affect significantly the formation of characteristic surface patterns.

  20. Field-induced transformations in the biaxial order of non-tilted phases in a bent-core smectic liquid crystal

    Science.gov (United States)

    Panarin, Y. P.; Nagaraj, Mamatha; Vij, J. K.; Keith, C.; Tschierske, C.

    2010-10-01

    The structural and electro-optic investigations of an achiral bent-core molecule in SmAPA phase, in which the polar directors in the neighboring layers are arranged anti-ferroelectrically, show that it undergoes transformation from one biaxial to another biaxial structure via a quasi-stable uniaxial structure on the application of the electric field. The non-continuous change in biaxiality is explained by an intermediate state in which the secondary directors in the neighboring layers are perpendicular to each other.

  1. Study on damage characteristics of marble under biaxial compression%双轴压缩状态下大理岩破坏特性的试验研究

    Institute of Scientific and Technical Information of China (English)

    李昂; 邵国建; 雷冬; 朱义欢

    2012-01-01

    Compression tests were conducted to Jinping marble in uniaxial and biaxial conditions. Based on stress-strain curves of different loading stress path, the characteristics of strain have been analyzed under different stress state while studying the process of cracks from being formed to being expanded which led the sample failure on the surface in the end. From uniaxial experiment results of different scales, the trend of size effect has been proved. It is revealed the failure format and regulation of Jinping marble in biaxial condition. Reference will be provided for practice project of underground curve in excavation.%针对锦屏一级水电工程深部大理岩,分别进行了单、双轴加载下的岩样试验.基于不同加载应力路径下岩样的应力-应变关系曲线,分析了大理岩在不同加载状态下的变形特征,研究了岩样表面裂缝形成、扩展直至破坏的全过程.从不同岩样尺寸的实验结果出发,探讨了尺寸效应对岩石强度的影响趋势,揭示了双轴应力条件下大理岩的破坏形式和破坏规律.所得结论可为实际地下洞室工程中的开挖效应分析提供参考依据.

  2. Comparison of calculation methods for the tunnel splitting at excited states of biaxial spin models

    Institute of Scientific and Technical Information of China (English)

    Cui Xiao-Bo; Chen Zhi-De

    2004-01-01

    We present the calculation and comparison of tunnel splitting at excited levels of biaxial spin models by various methods, including the generalized instanton method, the generalized path integral method for coherent spin states,the perturbation method, and the exact method by numerical diagonalization of the Hamiltonian. It is found that,for integer spin with spin number around 10, tunnel splitting predicted by the generalized path integral for coherent spin states is about 10-n times of the exact numerical result for the nth excited level, while the ratio of the results of the perturbation method and the exact numerical method diverges in the large spin limit. We thus conclude that the generalized instanton method is the best approximate way for calculating tunnel splitting in spin models.

  3. Biaxial lidar efficiency rising based on improving of spatial selectivity and stability against background radiation

    Energy Technology Data Exchange (ETDEWEB)

    Agishev, R.R.; Bajazitov, R.A.; Galeyev, M.M. [Kazan State Technical Univ., Tatarstan (Russian Federation). Dept. of Radioelectronic and Quantum Systems

    1996-12-31

    A criterion of spatial-angular efficiency (SAE) of remote electro-optical systems for atmosphere monitoring is formulated. The dependencies of the SAE from normalized range and minimal operating range for different optical receiving schemes of ground-based biaxial lidar are analyzed. It is shown that low SAE of traditional VIS and NIR systems are a main cause of a low signal-to-background-noise ratio at the photodetector input, the considerable measurements errors. and the following low accuracy of atmospheric optical parameters reconstruction. The most effective protection against sky background radiation in such systems consists in forming an angular field according to the introduced SAE criterion. Some approaches to achieve high value of the SAE-parameter for receiving system optimization are discussed.

  4. Measurement of refractive index of biaxial potassium titanyl phosphate crystal plate using reflection spectroscopic ellipsometry technique

    Indian Academy of Sciences (India)

    A K Chaudhary; A Molla; A Asfaw

    2009-10-01

    The paper reports the measurement of refractive indices and anisotropic absorption coefficients of biaxial potassium titanyl phosphate (KTP) crystal in the form of thin plate using reflection ellipsometry technique. This experiment is designed in the Graduate Optics Laboratory of the Addis Ababa University and He–Ne laser ( = 632.8 nm), diode laser ( = 670.0 nm) and temperature-tuned diode laser ( = 804.4 and 808.4 nm), respectively have been employed as source. The experimental data for , are fitted to the Marquardt–Levenberg theoretical model of curve fitting. The obtained experimental data of refractive indices are compared with different existing theoretical and experimental values of KTP crystals and found to be in good agreement with them.

  5. Voigt wave investigation in the KGd(WO4)2:Nd biaxial laser crystal

    Science.gov (United States)

    Brenier, Alain

    2015-07-01

    We have investigated the Nd3+-doped KGd(WO4)2 biaxial laser crystal for wave propagation directions in the vicinity of the optical axis at wavelengths tunable around 800 nm. The angular absorption distribution was found to be strongly anisotropic. Increasing absorption, the optical axis splits in two new ones able to propagate unchanged a left or a right circularly polarized light and able to propagate a circularly polarized Voigt wave with a linear spatial dependence. The intensities of the transmitted light in different configurations of polarizations were investigated. The angular displacement of the two optical axes versus the absorbed wavelengths was measured and explained with a single oscillator model. The light energy propagation was found distributed inside a crescent-shaped area.

  6. Development of a synchrotron biaxial tensile device for in situ characterization of thin films mechanical response

    International Nuclear Information System (INIS)

    We have developed on the DIFFABS-SOLEIL beamline a biaxial tensile machine working in the synchrotron environment for in situ diffraction characterization of thin polycrystalline films mechanical response. The machine has been designed to test compliant substrates coated by the studied films under controlled, applied strain field. Technological challenges comprise the sample design including fixation of the substrate ends, the related generation of a uniform strain field in the studied (central) volume, and the operations from the beamline pilot. Preliminary tests on 150 nm thick W films deposited onto polyimide cruciform substrates are presented. The obtained results for applied strains using x-ray diffraction and digital image correlation methods clearly show the full potentialities of this new setup.

  7. Fabrication of YBCO Coated Conductors on Biaxial Textured Metal Substrate by All-Sputtering

    Institute of Scientific and Technical Information of China (English)

    Xiao Han; Jing-Tan He; Jie Xiong; Bo-Wan Tao

    2008-01-01

    CeO2/YSZ/CeO2 buffer layers were prepared on biaxial textured Ni-5at.%W substrate by direct-current magnetron reactive sputtering with the optimum process. YBCO thin films were deposited on CeO2/YSZ/CeO2 buffered Ni-5at.%W substrate at temperature ranging from 500°C to 700°C by diode dc sputtering. By optimizing substrate temperature, pure c-axis oriented YBCO films were obtained. The microstructures of CeO2/YSZ/CeO2 buffer layers were characterized by X-ray diffraction. A smooth, dense and crack-free surface morphology was observed with scanning electron microscopy. The critical current density Jc about 0.75 MA/cm2 at 77 K was obtained.

  8. Impacts of virtual substrate doping on high frequency characteristics of biaxially strained Si PMOSFET

    Science.gov (United States)

    Khatami, Mohammad Mahdi; Shalchian, Majid; Kolahdouz, Mohammadreza

    2015-09-01

    Formation of a parasitic channel in biaxially strained Si channel p-MOSFET, degrades performance of the device. In this paper the effect of SiGe (virtual substrate) doping on formation of parasitic channel and high frequency characteristics of the strained MOSFET has been studied. Simulation results, indicate that increasing virtual substrate's doping from e.g. 4 × 1015 cm-3 to 4 × 1017 cm-3 effectively eliminates parasitic channel by reducing hole concentration from 1 × 1017 cm-3 to 1 × 1011 cm-3 in the parasitic channel. This improves MOSFET's characteristics including parasitic capacitances and channel length modulation. Also it has been demonstrated that the highest unity-gain bandwidth might be achieved at doping level of 4 × 1017 cm-3.

  9. 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.

  10. Abrasion resistance of biaxially oriented polypropylene films coated with nanocomposite hard coatings

    Science.gov (United States)

    Wang, Jing; Zhu, Yaofeng; Fu, Yaqin

    2013-11-01

    KMnO4-treated, functionalized, biaxially oriented polypropylene (BOPP) films coated with nano-silica hybrid material were synthesized. The abrasion resistance of the films was examined using a reciprocating fabric abrasion tester. Functional groups were confirmed by Fourier-transform infrared spectroscopy. Contact angle measurements were performed on the BOPP film surface to quantify the effectiveness of the functionalization. Results indicate that the abrasion resistance and roughness of the composite film were significantly affected by the modification of the BOPP film. Water surface contact angle of the modified BOPP films decreased from 90.1° to 71.4°,when KMnO4 concentration increased from 0 M to 0.25 M. Wettability of the BOPP films clearly improved after KMnO4 treatment. Abrasion resistance of the functionalized films coated with hybrid materials improved by 27.4% compared with that of the original film.

  11. Powder metallurgy for the fabrication of bi-axially textured Ni tapes for YBCO coated conductors

    International Nuclear Information System (INIS)

    Bi-axially textured Ni tapes for YBCO coated conductors were fabricated by forming, sintering, cold rolling and heat treatment of Ni powder compacts. The powder metallurgy process consists of filling of fine Ni powders in a rubber mold, cold isostatical pressing in a water chamber and sintering of the powder compacts. The sintered compacts were cold-rolled and made into tapes with a thickness of 100 micron and then heat-treated at 1000 deg. C for various time periods for the development of the (2 0 0) texture. The (2 0 0) texture of Ni tape was successfully formed through the optimization of the recrystallization heat treatment condition for the cold rolled Ni tapes. The full width half maximum of the Ni tapes was 8-10 deg. and the atomic force microscopy surface roughness was 3-5 nm

  12. UV protective zinc oxide coating for biaxially oriented polypropylene packaging film by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lahtinen, Kimmo, E-mail: kimmo.lahtinen@lut.fi [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Kääriäinen, Tommi, E-mail: tommi.kaariainen@colorado.edu [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Johansson, Petri, E-mail: petri.johansson@tut.fi [Paper Converting and Packaging Technology, Tampere University of Technology, P.O.Box 589, FI-33101 Tampere (Finland); Kotkamo, Sami, E-mail: sami.kotkamo@tut.fi [Paper Converting and Packaging Technology, Tampere University of Technology, P.O.Box 589, FI-33101 Tampere (Finland); Maydannik, Philipp, E-mail: philipp.maydannik@lut.fi [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Seppänen, Tarja, E-mail: tarja.seppanen@lut.fi [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Kuusipalo, Jurkka, E-mail: jurkka.kuusipalo@tut.fi [Paper Converting and Packaging Technology, Tampere University of Technology, P.O.Box 589, FI-33101 Tampere (Finland); Cameron, David C., E-mail: david.cameron@miktech.fi [ASTRaL, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland)

    2014-11-03

    Biaxially oriented polypropylene (BOPP) packaging film was coated with zinc oxide (ZnO) coatings by atomic layer deposition (ALD) in order to protect the film from UV degradation. The coatings were made at a process temperature of 100 °C using diethylzinc and water as zinc and oxygen precursors, respectively. The UV protective properties of the coatings were tested by using UV–VIS and infrared spectrometry, differential scanning calorimetry (DSC) and a mechanical strength tester, which characterised the tensile and elastic properties of the film. The results obtained with 36 and 67 nm ZnO coatings showed that the ZnO UV protective layer is able to provide a significant decrease in photodegradation of the BOPP film under UV exposure. While the uncoated BOPP film suffered a complete degradation after a 4-week UV exposure, the 67 nm ZnO coated BOPP film was able to preserve half of its original tensile strength and 1/3 of its elongation at break after a 6-week exposure period. The infrared analysis and DSC measurements further proved the UV protection of the ZnO coatings. The results show that a nanometre scale ZnO coating deposited by ALD is a promising option when a transparent UV protection layer is sought for polymer substrates. - Highlights: • Atomic layer deposited zinc oxide coatings were used as UV protection layers. • Biaxially oriented polypropylene (BOPP) film was well protected against UV light. • Formation of UV degradation products in BOPP was significantly reduced. • Mechanical properties of the UV exposed BOPP film were significantly improved.

  13. Transient and residual stresses in a pressable glass-ceramic before and after resin-cement coating determined using profilometry.

    LENUS (Irish Health Repository)

    2011-05-01

    The effect of heat-pressing and subsequent pre-cementation (acid-etching) and resin-cementation operative techniques on the development of transient and residual stresses in different thicknesses of a lithium disilicate glass-ceramic were characterised using profilometry prior to biaxial flexure strength (BFS) determination.

  14. Free vibration and biaxial buckling analysis of magneto-electro-elastic microplate resting on visco-Pasternak substrate via modified strain gradient theory

    Science.gov (United States)

    Jamalpoor, A.; Ahmadi-Savadkoohi, A.; Hosseini-Hashemi, Sh

    2016-10-01

    This paper deals with the theoretical analysis of free vibration and biaxial buckling of magneto-electro-elastic (MEE) microplate resting on Kelvin-Voigt visco-Pasternak foundation and subjected to initial external electric and magnetic potentials, using modified strain gradient theory (MSGT). Kirchhoff plate model and Hamilton’s principle are employed to extract the governing equations of motion. Governing equations were analytically solved to obtain clear closed-form expression for complex natural frequencies and buckling loads using Navier’s approach. Numerical results are presented to reveal variations of natural frequency and buckling load ratio of MEE microplate against different amounts of the length scale parameter, initial external electric and magnetic potentials, aspect ratio, damping and transverse and shear stiffness parameters of the visco-Pasternak foundation, length to thickness ratio, microplate thickness and higher modes. Numerical results of this study illustrate that by increasing thickness-to-material length scale parameter ratio, both natural frequency and buckling load ratio predicted by MSGT and modified couple stress theory are reduced because the non-dimensional length scale parameter tends to decrease the stiffness of structures and make them more flexible. In addition, results show that initial external electric and initial external magnetic potentials have no considerable influence on the buckling load ratio and frequency of MEE microplate as the microplate thickness increases.

  15. Effect of Biaxial Stretching at Temperatures and Strain Histories Comparable to Injection Stretch Blow Moulding on Tensile Modulus for Polyethylene Terephthalate (PET)

    Science.gov (United States)

    Tan, C. W.; Menary, G. H.; Harkin-Jones, E. M. A.; Armstrong, C. G.; Martin, P. J.

    2007-04-01

    This study is particularly relevant to the injection stretch blow moulding (ISBM) process where PET material is typically biaxially stretched to form bottles for the water and carbonated soft drinks industry. The aim of this paper is to investigate the effect of biaxial stretching on the mechanical properties of Polyethylene Terephthalate (PET) using a custom built biaxial testing machine. An initially amorphous PET sample was prepared via injection moulding to form a square sample (76mm × 76mm) suitable for stretching on the machine. This sample was then subjected to a series of biaxial tests (simultaneous and sequential) within a temperature range between 85°C and 110 °C, strain rates in the range of 1s-1 to 32s-1 and stretch ratios in the range of 1.5 to 3. Specimens were subsequently cut from the biaxial stretched sheets and used to measure the tensile modulus. Results showed that there is almost no effect found for strain rate and temperature on modulus development whilst stretch ratio and mode of deformation played the most important role on modulus development on PET under biaxial deformation.

  16. Statics and field-driven dynamics of transverse domain walls in biaxial nanowires under uniform transverse magnetic fields

    Science.gov (United States)

    Lu, Jie

    2016-06-01

    In this work, we report analytical results on transverse domain wall (TDW) statics and field-driven dynamics in quasi-one-dimensional biaxial nanowires under arbitrary uniform transverse magnetic fields (TMFs) based on the Landau-Lifshitz-Gilbert equation. Without axial driving fields, the static TDW should be symmetric about its center while twisted in its azimuthal angle distribution. By decoupling polar and azimuthal degrees of freedom, an approximate solution is provided which reproduces these features to a great extent. When an axial driving field is applied, the dynamical behavior of a TDW is viewed as the response of its static profile to external excitations. By means of the asymptotic expansion method, the TDW velocity in the traveling-wave mode is obtained, which provides the extent and boundary of the "velocity-enhancement" effect of TMFs on TDWs in biaxial nanowires. Finally, numerical simulations are performed and strongly support our analytics.

  17. Biaxial Strain in the Hexagonal Plane of MnAs Thin Films: The Key to Stabilize Ferromagnetism to Higher Temperature

    Science.gov (United States)

    Garcia, V.; Sidis, Y.; Marangolo, M.; Vidal, F.; Eddrief, M.; Bourges, P.; Maccherozzi, F.; Ott, F.; Panaccione, G.; Etgens, V. H.

    2007-09-01

    The α-β magnetostructural phase transition in MnAs/GaAs(111) epilayers is investigated by elastic neutron scattering. The in-plane parameter of MnAs remains almost constant with temperature from 100 to 420 K, following the thermal evolution of the GaAs substrate. This induces a temperature dependent biaxial strain that is responsible for an α-β phase coexistence and, more importantly, for the stabilization of the ferromagnetic α phase at a higher temperature than in the bulk. We explain the premature appearance of the β phase at 275 K and the persistence of the ferromagnetic α phase up to 350 K with thermodynamical arguments based on the MnAs phase diagram. It results that the biaxial strain in the hexagonal plane is the key parameter to extend the ferromagnetic phase well over room temperature.

  18. Electrically conducting oxide buffer layers on biaxially textured nickel alloy tapes by reel-to-reel MOCVD process

    International Nuclear Information System (INIS)

    Reel-to-reel MOCVD process for continuous growth of electrically conducting buffer layers on biaxially textured Ni5W tapes has been developed. The new buffer layer architechture is presented: 200 nm (La, Ba)2CuO4/40 nm (La, Ba)MnO3/Ni5W. Constituting layers with high structural quality have been grown on moving tapes (in plane FWHM ≤ 60 and out of plane FWHM ≤ 30)

  19. Reexamination of the mean-field phase diagram of biaxial nematic liquid crystals: Insights from Monte Carlo studies

    Science.gov (United States)

    Kamala Latha, B.; Jose, Regina; Murthy, K. P. N.; Sastry, V. S. S.

    2015-07-01

    Investigations of the phase diagram of biaxial liquid-crystal systems through analyses of general Hamiltonian models within the simplifications of mean-field theory (MFT), as well as by computer simulations based on microscopic models, are directed toward an appreciation of the role of the underlying molecular-level interactions to facilitate its spontaneous condensation into a nematic phase with biaxial symmetry. Continuing experimental challenges in realizing such a system unambiguously, despite encouraging predictions from MFT, for example, are requiring more versatile simulational methodologies capable of providing insights into possible hindering barriers within the system, typically gleaned through its free-energy dependences on relevant observables as the system is driven through the transitions. The recent paper from this group [Kamala Latha et al., Phys. Rev. E 89, 050501(R) (2014), 10.1103/PhysRevE.89.050501], summarizing the outcome of detailed Monte Carlo simulations carried out employing an entropic sampling technique, suggested a qualitative modification of the MFT phase diagram as the Hamiltonian is asymptotically driven toward the so-called partly repulsive regions. It was argued that the degree of (cross) coupling between the uniaxial and biaxial tensor components of neighboring molecules plays a crucial role in facilitating a ready condensation of the biaxial phase, suggesting that this could be a plausible factor in explaining the experimental difficulties. In this paper, we elaborate this point further, providing additional evidence from curious variations of free-energy profiles with respect to the relevant orientational order parameters, at different temperatures bracketing the phase transitions.

  20. Effect of Ceramic Surface Treatments After Machine Grinding on the Biaxial Flexural Strength of Different CAD/CAM Dental Ceramics

    OpenAIRE

    Bagheri, Hossein; Hooshmand, Tabassom; Aghajani, Farzaneh

    2015-01-01

    Objectives: This study aimed to evaluate the effect of different ceramic surface treatments after machining grinding on the biaxial flexural strength (BFS) of machinable dental ceramics with different crystalline phases. Materials and Methods: Disk-shape specimens (10mm in diameter and 1.3mm in thickness) of machinable ceramic cores (two silica-based and one zirconia-based ceramics) were prepared. Each type of the ceramic surfaces was then randomly treated (n=15) with different treatments as ...

  1. Domain Walls and Anchoring Transitions Mimicking Nematic Biaxiality in the Oxadiazole Bent-Core Liquid Crystal C7

    OpenAIRE

    Kim, Young-Ki; Cukrov, Greta; Xiang, Jie; Shin, Sung-Tae; Lavrentovich, Oleg D.

    2015-01-01

    We investigate the origin of secondary disclinations that were recently described as a new evidence of a biaxial nematic phase in an oxadiazole bent-core thermotropic liquid crystal C7. With an assortment of optical techniques such as polarizing optical microscopy, LC PolScope, and fluorescence confocal polarizing microscopy, we demonstrate that the secondary disclinations represent non-singular domain walls formed in an uniaxial nematic during the surface anchoring transition, in which surfa...

  2. Biaxial bending of slender HSC columns and tubes filled with concrete under short- and long-term loads: I) Theory

    OpenAIRE

    Rodríguez-Gutiérrez, Jose A.; Jose Dario Aristizabal-Ochoa

    2014-01-01

    An analytical method that calculates both the short- and long-term response of slender columns made of high-strength concrete (HSC) and tubes filled with concrete with generalized end conditions and subjected to transverse loads along the span and axial load at the ends (causing a single or double curvature under uniaxial or biaxial bending) is presented. The proposed method, which is an extension of a method previously developed by the authors, is capable of predicting not only the complete ...

  3. STRENGTH CRITERION FOR PLAIN CONCRETE UNDER MULTIAXIAL STRESS BASED ON DAMAGE POISSON'S RATIO

    Institute of Scientific and Technical Information of China (English)

    Ding Faxing; Yu Zhiwu

    2006-01-01

    A new unified strength criterion in the principal stress space has been proposed for use with normal strength concrete (NC) and high strength concrete (HSC) in compressioncompression-tension, compression-tension-tension, triaxial tension, and biaxial stress states. The study covers concrete with strengths ranging from 20 to 130 Mpa. The conception of damage Poisson's ratio is defined and the expression for damage Poisson's ratio is determined basically.The failure mechanism of concrete is illustrated, which points out that damage Poisson's ratio is the key to determining the failure of concrete. Furthermore, for the concrete under biaxial stress conditions, the unified strength criterion is simplified and a simplified strength criterion in the form of curves is also proposed. The strength criterion is physically meaningful and easy to calculate, which can be applied to analytic solution and numerical solution of concrete structures.

  4. First principles prediction of the electronic structure and carrier mobilities of biaxially strained molybdenum trioxide (MoO3)

    Science.gov (United States)

    Dandogbessi, Bruno S.; Akin-Ojo, Omololu

    2016-08-01

    The electronic band structures of unstrained and biaxially strained MoO3 were determined by first-principles density functional theory calculations. From the band structures, the effects of strain on the charge carrier mobilities were investigated. These mobilities were calculated based on deformation potential theory. First, we found that the electron effective masses of unstrained bulk pristine MoO3 are about three times smaller than the corresponding hole effective masses, and, second, the electron mobility is about ten times the hole mobility, making the compound an electron transport material. Our results also show that, when compressed biaxially, as the strain increases from 0% to 1.5%, the electron (hole) mobility increases by 0% to 53% (0% to 17%). On the other hand, the application of a biaxial tensile strain decreases the electron (hole) mobility by 65% to 0% (90% to 0%), as the tensile strain increases from 0% to 1.5 % . These changes are caused mainly by the fact that the carrier effective masses reduce (increase) upon application of compressive (tensile) strain. Only the acoustic-phonon limited carrier mobilities were computed; hence, the actual mobilities cannot be less than the values obtained in this work.

  5. Transverse-electric/transverse-magnetic polarization converter using 1D finite biaxial photonic crystal.

    Science.gov (United States)

    Ouchani, Noama; Bria, Driss; Djafari-Rouhani, Bahram; Nougaoui, Abdelkarim

    2007-09-01

    We show that by using a one-dimensional anisotropic photonic structure, it is possible to realize optical wave polarization conversion by reflection and transmission processes. Thus a single incident S(P) polarized plane wave can produce a single reflected P(S) polarized wave and a single transmitted P(S) polarized wave. This polarization conversion property can be fulfilled with a simple finite superlattice (SL) constituted of anisotropic dielectric materials. We discuss the appropriate choices of the material and geometrical properties to realize such structures. The transmission and reflection coefficients are calculated in the framework of the Green's function method. The amplitude and the polarization characteristics of reflected and transmitted waves are determined as functions of frequency, wave vector k(parallel) (parallel to the interface), and the orientations of the principal axes of the layers constituting the SL. Specific applications of these results are given for a SL consisting of alternating biaxial anisotropic layers NaNO(2)/SbSI sandwiched between two identical semi-infinite isotropic media. PMID:17767240

  6. The effects of surface contamination on the biaxially textured substrate for YBCO thick film deposition

    International Nuclear Information System (INIS)

    The epitaxial growth of YBa2Cu3O7-x (YBCO) films on biaxially textured substrates is one of the most promising technique for the fabrication of high current superconducting tapes operating at high temperature. Ni is very attractive as substrate because it easily develops a/ (100)[001] cubic texture. The low oxidation resistance represents the main drawback of the Ni substrate. In order to better assess the role of oxygen on the Ni substrates, a surface physics technique as Auger spectroscopy has been used. It has allowed to evaluate the amount of impurities for different Ni processing and exposure to the air. The results demonstrate that the surface contamination can be efficiently removed by RF sputtering before buffer layer deposition. This procedure allows to obtain CeO2/Pd/Ni architecture by laser ablation with a good epitaxy both of Pd and CeO2 films. On the contrary, when CeO2 is directly deposited on Ni a low epitaxy is obtained. The Auger analysis confirms that the formation of (111) NiO at the Ni-CeO2 interface hampers the epitaxial growth of the ceria film

  7. Biaxial Solar Tracking System Based on the MPPT Approach Integrating ICTs for Photovoltaic Applications

    Directory of Open Access Journals (Sweden)

    Raúl Gregor

    2015-01-01

    Full Text Available The smart grid and distributed generation based on renewable energy applications often involve the use of information and communication technology (ICT coupled with advanced control and monitoring algorithms to improve the efficiency and reliability of the electrical grid and renewable generation systems. Photovoltaic (PV systems have been recently applied with success in the fields of distributed generation due to their lower environmental impact where the electrical energy generation is related to the amount of solar irradiation and thus the angle of incident ray of the sun on the surface of the modules. This paper introduces an integration of ICTs in order to achieve the maximum power point tracking (MPPT using a biaxial solar tracking system for PV power applications. To generate the references for the digital control of azimuth and elevation angles a Global Positioning System (GPS by satellites is used which enables acquiring the geographic coordinates of the sun in real-time. As a total integration of the system a communication platform based on the 802.15.4 protocol for the wireless sensor networks (WSNs is adopted for supervising and monitoring the PV plant. A 2.4 kW prototype system is implemented to validate the proposed control scheme performance.

  8. Biaxial Dielectrophoresis Force Spectroscopy: A Stoichiometric Approach for Examining Intermolecular Weak Binding Interactions.

    Science.gov (United States)

    Park, In Soo; Kwak, Tae Joon; Lee, Gyudo; Son, Myeonggu; Choi, Jeong Woo; Choi, Seungyeop; Nam, Kihwan; Lee, Sei-Young; Chang, Woo-Jin; Eom, Kilho; Yoon, Dae Sung; Lee, Sangyoup; Bashir, Rashid; Lee, Sang Woo

    2016-04-26

    The direct quantification of weak intermolecular binding interactions is very important for many applications in biology and medicine. Techniques that can be used to investigate such interactions under a controlled environment, while varying different parameters such as loading rate, pulling direction, rupture event measurements, and the use of different functionalized probes, are still lacking. Herein, we demonstrate a biaxial dielectrophoresis force spectroscopy (BDFS) method that can be used to investigate weak unbinding events in a high-throughput manner under controlled environments and by varying the pulling direction (i.e., transverse and/or vertical axes) as well as the loading rate. With the BDFS system, we can quantitatively analyze binding interactions related to hydrogen bonding or ionic attractions between functionalized microbeads and a surface within a microfluidic device. Our BDFS system allowed for the characterization of the number of bonds involved in an interaction, bond affinity, kinetic rates, and energy barrier heights and widths from different regimes of the energy landscape. PMID:27007455

  9. The formation of vertically aligned biaxial tungsten nanorods using a novel shadowing growth technique

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, R [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States); Parker, T; Lu, T-M [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States); Lee, S [US Army Armament Research, Development and Engineering Center, Benet Labs, Watervliet, NY 12189 (United States)

    2009-11-18

    Biaxially textured tungsten nanorods (A15 crystal structure) have been grown by oblique angle DC magnetron sputtering using a novel rotation mode called 'two-step rotation'. In this mode, the substrate is given a fast rotation through 180{sup 0} at 90 rpm and this is followed by a rest period of 30 s. These nanorods are vertically aligned and have a [100] texture normal to the substrate along with preferential in-plane texture as shown by x-ray pole figure analysis. In contrast, the tungsten nanorods obtained without substrate rotation are slanted at an angle of {approx}45{sup 0} and have a [100] texture tilted 16{sup 0} with respect to the substrate normal. The flux is incident from two diametrically opposite points on the sample at an oblique angle, averaging out the growth into vertical columns that retain the in-plane texture. Scanning electron microscopy shows that the tungsten nanorods have a mixture of {l_brace}211{r_brace} and {l_brace}421{r_brace} crystal habits; these planes are both minimum surface energy planes for a cubic A15 crystal structure.

  10. A Parametric Study of Mixing in a Granular Flow a Bi-Axial Spherical Tumbler

    CERN Document Server

    Christov, Ivan C; Ottino, Julio M; Sturman, Rob

    2015-01-01

    We report on a computational parameter space study of mixing protocols for a half-full bi-axial spherical granular tumbler. The quality of mixing is quantified via the intensity of segregation (concentration variance) and computed as a function of three system parameters: angles of rotation about each tumbler axis and the flowing layer depth. Only the symmetric case is considered in which the flowing layer depth is the same for each rotation. We also consider the dependence on $\\bar{R}$, which parametrizes the concentric spheroids ("shells") that comprise the volume of the tumbler. The intensity of segregation is computed over 100 periods of the mixing protocol for each choice of parameters. Each curve is classified via a time constant, $\\tau$, and an asymptotic mixing value, $bias$. We find that most choices of angles and most shells throughout the tumbler volume mix well, with mixing near the center of the tumbler being consistently faster (small $\\tau$) and more complete (small $bias$). We conclude with ex...

  11. MTOR-independent induction of autophagy in trabecular meshwork cells subjected to biaxial stretch.

    Science.gov (United States)

    Porter, Kristine M; Jeyabalan, Nallathambi; Liton, Paloma B

    2014-06-01

    The trabecular meshwork (TM) is part of a complex tissue that controls the exit of aqueous humor from the anterior chamber of the eye, and therefore helps maintaining intraocular pressure (IOP). Because of variations in IOP with changing pressure gradients and fluid movement, the TM and its contained cells undergo morphological deformations, resulting in distention and stretching. It is therefore essential for TM cells to continuously detect and respond to these mechanical forces and adapt their physiology to maintain proper cellular function and protect against mechanical injury. Here we demonstrate the activation of autophagy, a pro-survival pathway responsible for the degradation of long-lived proteins and organelles, in TM cells when subjected to biaxial static stretch (20% elongation), as well as in high-pressure perfused eyes (30mmHg). Morphological and biochemical markers for autophagy found in the stretched cells include elevated LC3-II levels, increased autophagic flux, and the presence of autophagic figures in electron micrographs. Furthermore, our results indicate that the stretch-induced autophagy in TM cells occurs in an MTOR- and BAG3-independent manner. We hypothesize that activation of autophagy is part of the physiological response that allows TM cells to cope and adapt to mechanical forces. PMID:24583119

  12. Localized strain measurements of the intervertebral disc annulus during biaxial tensile testing.

    Science.gov (United States)

    Karakolis, Thomas; Callaghan, Jack P

    2015-01-01

    Both inter-lamellar and intra-lamellar failures of the annulus have been described as potential modes of disc herniation. Attempts to characterize initial lamellar failure of the annulus have involved tensile testing of small tissue samples. The purpose of this study was to evaluate a method of measuring local surface strains through image analysis of a tensile test conducted on an isolated sample of annular tissue in order to enhance future studies of intervertebral disc failure. An annulus tissue sample was biaxial strained to 10%. High-resolution images captured the tissue surface throughout testing. Three test conditions were evaluated: submerged, non-submerged and marker. Surface strains were calculated for the two non-marker conditions based on motion of virtual tracking points. Tracking algorithm parameters (grid resolution and template size) were varied to determine the effect on estimated strains. Accuracy of point tracking was assessed through a comparison of the non-marker conditions to a condition involving markers placed on tissue surface. Grid resolution had a larger effect on local strain than template size. Average local strain error ranged from 3% to 9.25% and 0.1% to 2.0%, for the non-submerged and submerged conditions, respectively. Local strain estimation has a relatively high potential for error. Submerging the tissue provided superior strain estimates. PMID:25145810

  13. Modeling of stored charge in metallized biaxially oriented polypropylene film capacitors based on charging current measurement.

    Science.gov (United States)

    Li, Hua; Wang, Bowen; Li, Zhiwei; Liu, De; Lin, Fuchang; Dai, Ling; Zhang, Qin; Chen, Yaohong

    2013-10-01

    Metallized biaxially oriented polypropylene film (BOPP) capacitors are widely used in pulsed power systems. When the capacitor is used as the energy storage equipment under high electric field, more charges should be provided to maintain the voltage of the capacitor. This should be ascribed to the completion of the slow polarization which may take several hours or even longer. This paper focuses on the stored charge in metallized BOPP film capacitors. The modeling of the stored charge by the equivalent conversion of circuits is conducted to analyse the slow polarization in the BOPP film. The 3-RC network is proposed to represent the time-dependent charge stored in the capacitor. A charging current measurement system is established to investigate the charge storage property of the capacitor. The measurement system can measure the long time charging current with a sampling rate of 300 Hz. The total charge calculated by the charging current indicates that the stored charge in the capacitor under the electric field of 400 V/μm is 13.5% larger than the product of the voltage and the capacitance measured by the AC bridge. The nonlinear effect of the electric field on the slow polarization charge is also demonstrated. And the simulation of charge storage based on the 3-RC network can match well with the trend of the stored charge increasing with the time. PMID:24182144

  14. Numerical analysis of soil-rock mixture's meso-mechanics based on biaxial test

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hai-yang; XU Wen-jie; YU Yu-zhen

    2016-01-01

    Soil-rock mixture(S-RM)is a widely distributed geotechnical medium composed of "soil" and "rock block" different both in size and strength. Internal rock blocks form special and variable meso-structural characteristics of S-RM. The objective of this work was to study the control mechanism of meso-structural characteristics on mechanical properties of S-RM. For S-RM containing randomly generated polygonal rock blocks, a series of biaxial tests based on DEM were conducted. On the basis of research on the effects of rock blocks' breakability and sample lateral boundary type (rigid, flexible) on macroscopic mechanical behavior of S-RM, an expanded Mohr-Coulomb criterion in power function form was proposed to represent the strength envelop. At the mesoscopic level, the variations of meso-structure such as rotation of rock block, and the formation mechanism and evolution process of the shear band during tests were investigated. The results show that for S-RM with a high content of rock block, translation, rotating and breakage of rock blocks have crucial effects on mechanical behavior of S-RM. The formation and location of the shear band inside S-RM sample are also controlled by breakability and arrangement of rock blocks.

  15. A numerical study of macro-mesoscopic mechanical properties of gangue backfill under biaxial compression

    Institute of Scientific and Technical Information of China (English)

    Huang Zhimin; Ma Zhanguo; Zhang Lei; Gong Peng; Zhang Yankun; Liu Fei

    2016-01-01

    Based on the Particle Flow Code (PFC2D) program, we set up gangue backfill models with different gangue contents and bond strength, and studied the stress–strain behaviours, the pattern of shear band and force chains, motion and fragmentation of particles under biaxial compression. The results show that when the bond strength or contents of gangue are high, the peak strength is high and the phenomena of post-peak softening and fluctuation are obvious. When gangue contents are low, the shape of the shear band is sym-metrical and most strong force chains transfer in soil particles. With an increase in gangue content, the shape of the shear band becomes irregular and the majority of strong force chains turn to transfer in gangue particles gradually, most of which distribute along the axial direction. When the gangue content is higher than 50%, the interconnectivity of strong force chains decreases gradually;at the same time, the strong force chains become tilted and the stability of the system tends to decrease. With an increase in external loading, the coordination numbers of the system increase at first and then decrease and the main pattern of force chains changes into columnar from annular. However, after the forming of the advanta-geous shear band, the force chains external to the shear band maintain their columnar shape while the inner ones bend obviously. As a result, annular force chains form.

  16. Modeling of stored charge in metallized biaxially oriented polypropylene film capacitors based on charging current measurement

    Science.gov (United States)

    Li, Hua; Wang, Bowen; Li, Zhiwei; Liu, De; Lin, Fuchang; Dai, Ling; Zhang, Qin; Chen, Yaohong

    2013-10-01

    Metallized biaxially oriented polypropylene film (BOPP) capacitors are widely used in pulsed power systems. When the capacitor is used as the energy storage equipment under high electric field, more charges should be provided to maintain the voltage of the capacitor. This should be ascribed to the completion of the slow polarization which may take several hours or even longer. This paper focuses on the stored charge in metallized BOPP film capacitors. The modeling of the stored charge by the equivalent conversion of circuits is conducted to analyse the slow polarization in the BOPP film. The 3-RC network is proposed to represent the time-dependent charge stored in the capacitor. A charging current measurement system is established to investigate the charge storage property of the capacitor. The measurement system can measure the long time charging current with a sampling rate of 300Hz. The total charge calculated by the charging current indicates that the stored charge in the capacitor under the electric field of 400 V/μm is 13.5% larger than the product of the voltage and the capacitance measured by the AC bridge. The nonlinear effect of the electric field on the slow polarization charge is also demonstrated. And the simulation of charge storage based on the 3-RC network can match well with the trend of the stored charge increasing with the time.

  17. EFFECT OF RESIDUAL STRESS ON THE MARTENSITIC TRANS- FORMATION OF SPUTTER-DEPOSITED SMA THIN FILMS

    Institute of Scientific and Technical Information of China (English)

    L. Wang; D. Xu; B.C. Cai

    2002-01-01

    TiNi thin films were sputter-deposited on circular single-crystal silicon substrates un-der various sputtering parameters. The crystal structure and residual stress of the as-deposited films were determined by X-ray diffraction and substrate-curvature method.The phenomenon of stress-suppressed martensitic transformation was observed. It isconsidered that the residual stresses in SMA thin films based on circular substratesact as balanced biaxial tensile stresses. The status of equilibrant delays the align-ment of self-accommodated variants and the volume shrinkage during the martensitictransformation.

  18. Modeling of CMUTs with Multiple Anisotropic Layers and Residual Stress

    DEFF Research Database (Denmark)

    Engholm, Mathias; Thomsen, Erik Vilain

    2014-01-01

    Usually the analytical approach for modeling CMUTs uses the single layer plate equation to obtain the deflection and does not take anisotropy and residual stress into account. A highly accurate model is developed for analytical characterization of CMUTs taking an arbitrary number of layers...... and residual stress into account. Based on the stress-strain relation of each layer and balancing stress resultants and bending moments, a general multilayered anisotropic plate equation is developed for plates with an arbitrary number of layers. The exact deflection profile is calculated for a circular...... clamped plate of anisotropic materials with residual bi-axial stress. From the deflection shape the critical stress for buckling is calculated and by using the Rayleigh-Ritz method the natural frequency is estimated....

  19. Stress-strain curves for different loading paths and yield loci of aluminum alloy sheets

    Institute of Scientific and Technical Information of China (English)

    WU Xiang-dong; WAN Min; HAN Fei; WANG Hai-bo

    2006-01-01

    To carry out biaxial tensile test in sheet metal, the biaxial tensile testing system was established. True stress-true strain curves of three kinds of aluminum alloy sheets for loading ratios of 4:1, 4:2, 4:3, 4:4, 3:4, 2:4 and 1:4 were obtained by conducting biaxial tensile test in the established testing systems. It shows that the loading path has a significant influence on the stress-strain curves and as the loading ratio increases from 4:1 to 4:4, the stress-strain curve becomes higher and n-value becomes larger.Experimental yield points for three aluminum alloy sheets from 0.2% to 2% plastic strain were determined based on the equivalent plastic work. And the geometry of the experimental yield loci were compared with the yield loci calculated from several existing yield criteria. The analytical result shows that the Barlat89 and Hosford yield criterion describe the general trends of the experimental yield loci of aluminum alloy sheets well, whereas the Mises yield criterion overestimates the yield stress in all the contours.

  20. Dependence of electronic properties of germanium on the in-plane biaxial tensile strains

    International Nuclear Information System (INIS)

    The hybrid HSE06 functional with the spin–orbit coupling effects is used to calculate the habituation of the electronic properties of Ge on the (0 0 1), (1 1 1), (1 0 1) in-plane biaxial tensile strains (IPBTSs). Our motivation is to explore the nature of electronic properties of tensile-strained Ge on different substrate orientations. The calculated results demonstrate that one of the most effective and practical approaches for transforming Ge into a direct transition semiconductor is to introduce (0 0 1) IPBTS to Ge. At 2.3% (0 0 1) IPBTS, Ge becomes a direct bandgap semiconductor with 0.53 eV band gap, in good agreement with the previous theoretical and experimental results. We find that the (1 1 1) and (1 0 1) IPBTSs are not efficient since the shear strain and inner displacement of atoms introduced by them quickly decrease the indirect gap of Ge. By investigating the dependence of valence band spin–orbit splitting on strain, we prove that the dependency relationship and the coupled ways between the valence-band states of tensile-strained Ge are closely related to the symmetry of strain tensor, i.e., the symmetry of the substrate orientation. The first- and second-order coefficients describing the dependence of indirect gap, direct gap, the valence band spin–orbit coupling splitting, and heavy-hole–light-hole splitting of Ge on IPBTSs have been obtained by the least squares polynomial fitting. These coefficients are significant to quantitatively modulate the electronic properties of Ge by tensile strain and design tensile-strained Ge devices by semiconductor epitaxial technique

  1. SIMULATIONS OF MULTIPLE SOURCES IN BIAXIALLY STRESSED BOREHOLES: 2.5 DIMENSIONAL FINITE DIFFERENCE METHOD. (R825225)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  2. Development of a biaxial compression device for biological samples: preliminary experimental results for a closed cell foam.

    Science.gov (United States)

    Little, J P; Tevelen, G; Adam, C J; Evans, J H; Pearcy, M J

    2009-07-01

    Biological tissues are subjected to complex loading states in vivo and in order to define constitutive equations that effectively simulate their mechanical behaviour under these loads, it is necessary to obtain data on the tissue's response to multiaxial loading. Single axis and shear testing of biological tissues is often carried out, but biaxial testing is less common. We sought to design and commission a biaxial compression testing device, capable of obtaining repeatable data for biological samples. The apparatus comprised a sealed stainless steel pressure vessel specifically designed such that a state of hydrostatic compression could be created on the test specimen while simultaneously unloading the sample along one axis with an equilibrating tensile pressure. Thus a state of equibiaxial compression was created perpendicular to the long axis of a rectangular sample. For the purpose of calibration and commissioning of the vessel, rectangular samples of closed cell ethylene vinyl acetate (EVA) foam were tested. Each sample was subjected to repeated loading, and nine separate biaxial experiments were carried out to a maximum pressure of 204 kPa (30 psi), with a relaxation time of two hours between them. Calibration testing demonstrated the force applied to the samples had a maximum error of 0.026 N (0.423% of maximum applied force). Under repeated loading, the foam sample demonstrated lower stiffness during the first load cycle. Following this cycle, an increased stiffness, repeatable response was observed with successive loading. While the experimental protocol was developed for EVA foam, preliminary results on this material suggest that this device may be capable of providing test data for biological tissue samples. The load response of the foam was characteristic of closed cell foams, with consolidation during the early loading cycles, then a repeatable load-displacement response upon repeated loading. The repeatability of the test results demonstrated the

  3. Development of a methodology for the assessment of shallow-flaw fracture in nuclear reactor pressure vessels: Generation of biaxial shallow-flaw fracture toughness data

    Energy Technology Data Exchange (ETDEWEB)

    McAfee, W.J.; Bass, B.R.; Bryson, J.W.

    1998-07-01

    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. Shallow-flaw fracture toughness of RPV material has been shown to be higher than that for deep flaws, because of the relaxation of crack-tip constraint. This report describes the preliminary test results for a series of cruciform specimens with a uniform depth surface flaw. These specimens are all of the same size with the same depth flaw. Temperature and biaxial load ratio are the independent variables. These tests demonstrated that biaxial loading could have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. Through that temperature range, the effect of full biaxial (1:1) loading on uniaxial, shallow-flaw toughness varied from no effect near the lower shelf to a reduction of approximately 58% at higher temperatures.

  4. Catalytic surface modification of roll-milled poly(ε-caprolactone) biaxially stretched to ultra-thin dimension

    International Nuclear Information System (INIS)

    A novel roll-milling polymer processing technique along with biaxial stretching was used to fabricate 10 μm thick poly(ε-caprolactone) films. A less invasive collagen surface modification was used, involving a reaction between corona-preactivated membranes and ferrous-containing acrylic acid solution at the low temperature of 42 oC. Successful modified films were characterized by Toluidine Blue O assay and X-ray photoelectron spectroscopy. Human umbilical vein endothelial cells also showed both higher proliferation rate and differentiated cobblestone morphology on these collagen-immobilized substrates

  5. Limit load solution for an edge cracked plate under combined independent bi-axial membrane and bending

    International Nuclear Information System (INIS)

    A limit load solution for an edge cracked plate that includes any combination of biaxial bending and membrane loading is developed in the study. This solution will then be compared to the solution within the Miller Compendium and that obtained from Finite Element (FE) analyses. The solutions applicability to a cylinder will also be considered through the use of FE modeling. Through these comparisons it is hoped that the derived limit load solution can be validated and guidance for its applicability to a cylinder provided

  6. Biaxial Strain in the Hexagonal Plane of MnAs Thin Films: The Key to Stabilize Ferromagnetism to Higher Temperature

    OpenAIRE

    Garcia, V.; Sidis, Y.; Marangolo, M.; Vidal, F.; Eddrief, M; Bourges, P.; Maccherozzi, F.; Ott, F.; Panaccione, G.; Etgens, V. H.

    2007-01-01

    The alpha-beta magneto-structural phase transition in MnAs/GaAs(111) epilayers is investigated by elastic neutron scattering. The in-plane parameter of MnAs remains almost constant with temperature from 100 K to 420 K, following the thermal evolution of the GaAs substrate. This induces a temperature dependent biaxial strain that is responsible for an alpha-beta phase coexistence and, more important, for the stabilization of the ferromagnetic alpha-phase at higher temperature than in bulk. We ...

  7. Biaxial bending of slender hsc columns and tubes filled with concrete under short- and long-term loads: ii) verification

    OpenAIRE

    Rodríguez-Gutiérrez, Jose A.; ARISTIZABAL-OCHOA, JOSE DARIO

    2014-01-01

    An analytical method that calculates both the short- and long-term response of slender columns made of high-strength concrete (HSC) and of tubes filled with concrete with generalized end conditions that are subjected to transverse loads along the span and to axial loads at the ends (causing single- or double-curvature under uniaxial or biaxial bending) is presented in a companion paper. The columns that can be analyzed with this method include those with solid and hollow rectangular, circular...

  8. Active-flux based motion sensorless vector control of biaxial excitation generator/motor for automobiles (BEGA)

    DEFF Research Database (Denmark)

    Coroban-Schramel, Vasile; Boldea, Ion; Andreescu, Gheorghe-Daniel;

    2009-01-01

    the active-flux concept the estimated rotor position is given by the sum of the active flux angle and torque angle. The active flux is calculated by subtracting the term Lq i s from the estimated stator flux vector. The experimental results validate the active flux-principle and show good performance......This paper proposes a novel, active-flux based, motion-sensorless vector control structure for biaxial excitation generator for automobiles (BEGA) for wide speed range operation. BEGA is a hybrid excited synchronous machine having permanent magnets on q-axis and a dc excitation on daxis. Using...

  9. Modification of valence-band symmetry and Auger threshold energy in biaxially compressed InAs1-xSbx

    International Nuclear Information System (INIS)

    Strained-layer superlattices (SLS's) with biaxially compressed InAs1-xSbx were characterized using magnetophotoluminescence and compared with unstrained InAs1-xSbx alloys. Holes in the SLS exhibited a decrease in effective mass, approaching that of the electrons. In the two-dimensional limit, a large increase in the Auger threshold energy accompanies this strain-induced change in SLS valence-band symmetry. Correspondingly, the activation energy for nonradiative recombination in the SLS's displayed a marked increase compared with that of the unstrained alloys. Strained-layer superlattices and alloy activation energies are in agreement with estimated Auger threshold energies

  10. Catalytic surface modification of roll-milled poly({epsilon}-caprolactone) biaxially stretched to ultra-thin dimension

    Energy Technology Data Exchange (ETDEWEB)

    Foo, H.L. [Graduate Programme in Bioengineering, National University of Singapore (Singapore); Bionic Materials Technology Group, Biomaterials Center, National Institute for Materials Science (Japan); Taniguchi, A. [Bionic Materials Technology Group, Biomaterials Center, National Institute for Materials Science (Japan); Yu, H. [Graduate Programme in Bioengineering, National University of Singapore (Singapore); Department of Physiology, National University of Singapore (Singapore); Okano, T. [Bionic Materials Technology Group, Biomaterials Center, National Institute for Materials Science (Japan); Institute of Biomedical Engineering, Tokyo Women' s Medical University (Japan); Teoh, S.H. [Graduate Programme in Bioengineering, National University of Singapore (Singapore) and Department of Mechanical Engineering, National University of Singapore (Singapore)]. E-mail: mpetsh@nus.edu.sg

    2007-03-15

    A novel roll-milling polymer processing technique along with biaxial stretching was used to fabricate 10 {mu}m thick poly({epsilon}-caprolactone) films. A less invasive collagen surface modification was used, involving a reaction between corona-preactivated membranes and ferrous-containing acrylic acid solution at the low temperature of 42 {sup o}C. Successful modified films were characterized by Toluidine Blue O assay and X-ray photoelectron spectroscopy. Human umbilical vein endothelial cells also showed both higher proliferation rate and differentiated cobblestone morphology on these collagen-immobilized substrates.

  11. Time-dependent strains and stresses in a pumpkin balloon

    Science.gov (United States)

    Gerngross, T.; Xu, Y.; Pellegrino, S.

    This paper presents a study of pumpkin-shaped superpressure balloons consisting of gores made from a thin polymeric film attached to high stiffness meridional tendons This type of design is being used for the NASA ULDB balloons The gore film shows considerable time-dependent stress relaxation whereas the behaviour of the tendons is essentially time-independent Upon inflation and pressurization the instantaneous i e linear-elastic strain and stress distributions in the film show significantly higher values in the meridional direction However over time and due to the biaxial visco-elastic stress relaxation of the the gore material the em hoop strains increase and the em meridional stresses decrease whereas the em remaining strain and stress components remain substantially unchanged These results are important for a correct assessment of the structural integrity of a pumpkin balloon in a long-duration mission both in terms of the material performance and the overall stability of the shape of the balloon An experimental investigation of the time dependence of the biaxial strain distribution in the film of a 4 m diameter 48 gore pumpkin balloon is presented The inflated shape of selected gores has been measured using photogrammetry and the time variation in strain components at some particular points of these gores has been measured under constant pressure and temperature The results show good correlation with a numerical study using the ABAQUS finite-element package that includes a widely used model of

  12. Effect of sandblasting and residual stress on strength of zirconia for restorative dentistry applications

    OpenAIRE

    Kiran Chintapalli, Ravi; Mestra Rodríguez, Álvaro Miguel; García Marro, Fernando; Anglada Gomila, Marcos Juan

    2014-01-01

    Sandblasting is a commonly used surface treatment technique for dental crowns to improve the adhesion of the mating parts of a restoration. The goal of this work is to study the effect of different sandblasting conditions on the mechanical properties of 3 mol% yttria stabilized tetragonal zirconia (3Y-TZP), such as biaxial strength, surface elastic modulus, contact hardness and residual stresses induced by sandblasting. The specimens were sandblasted considering two different particle sizes (...

  13. Enhanced carrier mobility and direct tunneling probability of biaxially strained Ge{sub 1−x}Sn{sub x} alloys for field-effect transistors applications

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lei; Liang, Renrong, E-mail: liangrr@tsinghua.edu.cn, E-mail: junxu@tsinghua.edu.cn; Wang, Jing; Xu, Jun, E-mail: liangrr@tsinghua.edu.cn, E-mail: junxu@tsinghua.edu.cn [Tsinghua National Laboratory for Information Science and Technology, Institute of Microelectronics, Tsinghua University, Beijing 100084 (China)

    2015-05-14

    The carrier transport and tunneling capabilities of biaxially strained Ge{sub 1−x}Sn{sub x} alloys with (001), (110), and (111) orientations were comprehensively investigated and compared. The electron band structures of biaxially strained Ge{sub 1−x}Sn{sub x} alloys were calculated by the nonlocal empirical pseudopotential method and the modified virtual crystal approximation was adopted in the calculation. The electron and hole effective masses at the band edges were extracted using a parabolic line fit. It is shown that the applied biaxial strain and the high Sn composition are both helpful for the reduction of carrier effective masses, which leads to the enhanced carrier mobility and the boosted direct band-to-band-tunneling probability. Furthermore, the strain induced valance band splitting reduces the hole interband scattering, and the splitting also results in the significantly enhanced direct tunneling rate along the out-of-plane direction compared with that along the in-plane direction. The biaxially strained (111) Ge{sub 1−x}Sn{sub x} alloys exhibit the smallest band gaps compared with (001) and (110) orientations, leading to the highest in-plane and out-of-plane direct tunneling probabilities. The small effective masses on (110) and (111) planes in some strained conditions also contribute to the enhanced carrier mobility and tunneling probability. Therefore, the biaxially strained (110) and (111) Ge{sub 1−x}Sn{sub x} alloys have the potential to outperform the corresponding (001) Ge{sub 1−x}Sn{sub x} devices. It is important to optimize the applied biaxial strain, the Sn composition, and the substrate orientation for the design of high performance Ge{sub 1−x}Sn{sub x} field-effect transistors.

  14. Effect of saliva and blood contamination on the bi-axial flexural strength and setting time of two calcium-silicate based cements: Portland cement and biodentine.

    Science.gov (United States)

    Alhodiry, W; Lyons, M F; Chadwick, R G

    2014-03-01

    This study evaluated the effect of contamination with saliva and blood on the bi-axial flexural strength and setting time of pure gray Portland cement and Biodentine (Septodont, Allington, UK). A one-way ANOVA showed that contamination caused no significant difference between the cements in bi-axial flexural strength (P> 0.05). However there was a significant difference in setting time (Pcement taking longer than Biodentine, regardless of the contaminant, and contamination with blood increased the setting time of both materials. Biodentine was similar in strength to Portland cement, but had a shorter setting time for both contaminated and non-contaminated samples.

  15. Modeling of plates with multiple anisotropic layers and residual stress

    DEFF Research Database (Denmark)

    Engholm, Mathias; Pedersen, Thomas; Thomsen, Erik Vilain

    2016-01-01

    Usually the analytical approach for modeling of plates uses the single layer plate equation to obtain the deflection and does not take anisotropy and residual stress into account. Based on the stress–strain relation of each layer and balancing stress resultants and bending moments, a general...... multilayered anisotropic plate equation is developed for plates with an arbitrary number of layers. The exact deflection profile is calculated for a circular clamped plate of anisotropic materials with residual bi-axial stress.From the deflection shape the critical stress for buckling is calculated......, and an excellent agreement between the two models is seen with a relative difference of less than 2% for all calculations. The model was also used to extract the cell capacitance, the parasitic capacitance and the residual stress of a pressure sensor composed of a multilayered plate of silicon and silicon oxide...

  16. Preparation of Porous GaN Buffer and Its Influence on the Residual Stress of GaN Epilayers Grown by Hydride Vapor Phase Epitaxy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The preparation of porous structure on the molecular beam epitaxy (MBE)-grown mixed-polarity GaN epilayers was reported by using the wet chemical etching method. The effect of this porous structure on the residual stress of subsequent-growth GaN epilayers was studied by Raman and photoluminescence (PL) spectrum.Substantial decrease in the biaxial stresse can be achieved by employing the porous buffers in the hydride vapour phase epitaxy (HVPE) epilayer growth.

  17. Electronic and optical properties of beryllium sulfide monolayer: Under stress and strain conditions

    Science.gov (United States)

    Jalilian, Jaafar; Safari, Mandana

    2016-10-01

    Electronic and optical properties of two-dimensional graphene-like structure of beryllium sulfide (BeS) have been studied in the framework of the density functional theory. Different values of stress and strain are exerted for tuning electronic and optical parameters. The electronic results show that both biaxial stress and strain effects cause band gap reduction with different rates. Also, we have red and blue shifts in the optical absorption spectrum peaks by applying strain and stress, respectively. Our results express that BeS monolayer can be the promising candidate for the future nano-devices.

  18. Influence of uniaxial, biaxial and plane strain pre-straining on the dynamic tensile properties of high strength sheet steels

    Science.gov (United States)

    Larour, P.; Verleysen, P.; Bleck, W.

    2006-08-01

    The influence of pre-straining and microstructure on the dynamic properties of car body high strength steels has been investigated at room temperature. The mechanical properties of a dual phase steel DP600, a TRIP steel TRIP700 and an austenitic steel AISI 301LN2B (1.4318) have been determined performing high speed servohydraulic and split-Hopkinson bar tensile tests in the strain rate range from 0.005s-1 up to 950s-1. The pre-straining modes and levels, respectively 10% uniaxial, 10% plane strain and 5% biaxial pre-straining, have been chosen in this investigation according to industrial use. 10% plane strain pre-straining brings the highest increase of yield and tensile strength values. 5% biaxial and 10% uniaxial pre-straining have similar effect on strength properties. The austenitic steel presents a pronounced minimum for tensile strength values at around 1/s. A combination of adiabatic heating and exothermic γ to α' transformation produces some significant softening effects in the austenitic steel grade.

  19. Biaxially oriented CdTe films on glass substrate through nanostructured Ge/CaF2 buffer layers

    Science.gov (United States)

    Lord, R. J.; Su, P.-Y.; Bhat, I.; Zhang, S. B.; Lu, T.-M.; Wang, G.-C.

    2015-09-01

    Heteroepitaxial CdTe films were grown by metal organic chemical vapor deposition on glass substrates through nanostructured Ge/CaF2 buffer layers which were biaxially oriented. It allows us to explore the structural properties of multilayer biaxial semiconductor films which possess small angle grain boundaries and to test the principle of a solar cell made of such low-cost, low-growth-temperature semiconductor films. Through the x-ray diffraction and x-ray pole figure analysis, the heteroepitaxial relationships of the mutilayered films are determined as [111] in the out-of-plane direction and CdTe//Ge//{ }{{{CaF}}2} in the in-plane direction. The I-V curves measured from an ITO/CdS/CdTe/Ge/CaF2/glass solar cell test structure shows a power conversion efficiency of ˜η = 1.26%, illustrating the initial success of such an approach. The observed non-ideal efficiency is believed to be due to a low shunt resistance and high series resistance as well as some residual large-angle grain boundary effects, leaving room for significant further improvement.

  20. Toward a biaxial model of "bipolar" affective disorders: further exploration of genetic, molecular and cellular substrates.

    Science.gov (United States)

    Askland, Kathleen

    2006-08-01

    Current epidemiologic and genetic evidence strongly supports the heritability of bipolar disease. Inconsistencies across linkage and association analyses have been primarily interpreted as suggesting polygenic, nonMendelian and variably-penetrant inheritance (i.e., in terms of interacting disease models). An equally-likely explanation for this genetic complexity is that trait, locus and allelic heterogeneities (i.e., a heterogeneous disease model) are primarily responsible for observed variability at the population level. The two models of genetic complexity are not mutually-exclusive, and are in fact likely to co-exist both in trait determination and disease expression. However, the current model proposes that, while both types of complex genetics are likely central to observable affective trait spectra, inheritance patterns, gross phenotypic categories and treatment-responsiveness in affective disease (as well as the widespread inconsistencies across such studies) may be primarily explained in terms of a heterogeneous disease model. Gene-gene, gene-protein and protein-protein interactions, then, are most likely to serve as trait determinants and 'phenotypic modifiers' rather than as primary pathogenic determinants. Moreover, while locus heterogeneity indicates the presence of multiple susceptibility genes at the population level, it does not necessitate polygenic inheritance at the individual or pedigree level. Rather, it is compatible with the possibility of mono- or bigenic determination of disease susceptibility within individuals/pedigrees. More specifically, the biaxial model proposes that integration of specific findings from genetic linkage and association studies, ion channels research as well as pharmacologic mechanism, phenotypic specificity and effectiveness studies suggests that each gene of potential etiologic significance in primary affective illness might be categorized into one of two classes, according to their primary role in neuronal

  1. Tuning of the electronic and optical properties of single-layer indium nitride by strain and stress

    Science.gov (United States)

    Jalilian, Jaafar; Naseri, Mosayeb; Safari, Shima; Zarei, Mina

    2016-09-01

    Using first principles calculations, electronic and optical properties of indium nitride graphene-like structure have been studied under various stress and strain values. The results exhibit that this compound in the range of ±6 applied biaxial strain remains a direct band gap semiconductor. Also, exerting stress and strain reduces the energy band gap of the considered materials. The optical calculations illustrate that applying stress and strain on system results in blue and red shift in optical spectra. All obtained results presented that we can tune the optoelectronic properties of indium nitride by applying stress and strain.

  2. Evaluation of Crack-tip Stress in Titanium Oxide Film Using Piezo-spectroscopy Methods

    Institute of Scientific and Technical Information of China (English)

    WAN Keshu; ZHU Wenliang; PEZZOTTI Giuseppe; MIAO Lei; TANEMURA Sakae

    2004-01-01

    The biaxial piezo-spectroscopic coefficient of 530 nm cathodoluminescence band of polycrystalline anatase titanium oxide film was measured using a local calibration procedure. Firstly, the crack-tip stress intensity factor in titanium oxide was measured from the crack opening displacement of a Vickers indentation crack using both Irwin's formula and Fett's formula, and the validity of these two formulas was evaluated. The obtained value was about Ktip =1 MPa √m. In such a brittle material, the fracture toughness can be considered to be very close to the stress intensity factor measured in an equilibrium indentation crack (Ktip= Kc). From the Ktip value, we calculated the stress distribution ahead of the crack tip using principles of linear elastic fracture mechanics. An important finding was that the cathodoluminescence 530 nm band that originated from excitons self-trapped on TiO6 octahedra, is sensitive to stress. Using the shift of this peak and the calculated stress from linear elastic fracture mechanics, the biaxial piezo-spectroscopic coefficient of this band was determined (40 nm/GPa with a 20% error rate). Using this piezo-spectroscopic coefficient, approximate stress maps can be collected of unknown stress fields within thin films with high spatial resolution into the scanning electron microscope. The present experiments provide a vivid example of quantitative micromechanical stress analysis by piezo-spectroscopic techniques.

  3. Biaxial mechanics and inter-lamellar shearing of stem-cell seeded electrospun angle-ply laminates for annulus fibrosus tissue engineering.

    Science.gov (United States)

    Driscoll, Tristan P; Nakasone, Ryan H; Szczesny, Spencer E; Elliott, Dawn M; Mauck, Robert L

    2013-06-01

    The annulus fibrosus (AF) of the intervertebral disk plays a critical role in vertebral load transmission that is heavily dependent on the microscale structure and composition of the tissue. With degeneration, both structure and composition are compromised, resulting in a loss of AF mechanical function. Numerous tissue engineering strategies have addressed the issue of AF degeneration, but few have focused on recapitulation of AF microstructure and function. One approach that allows for generation of engineered AF with appropriate (+/-)30° lamellar microstructure is the use of aligned electrospun scaffolds seeded with mesenchymal stem cells (MSCs) and assembled into angle-ply laminates (APL). Previous work indicates that opposing lamellar orientation is necessary for development of near native uniaxial tensile properties. However, most native AF tensile loads are applied biaxially, as the disk is subjected to multi-axial loads and is constrained by its attachments to the vertebral bodies. Thus, the objective of this study was to evaluate the biaxial mechanical response of engineered AF bilayers, and to determine the importance of opposing lamellar structure under this loading regime. Opposing bilayers, which replicate native AF structure, showed a significantly higher modulus in both testing directions compared to parallel bilayers, and reached ∼60% of native AF biaxial properties. Associated with this increase in biaxial properties, significantly less shear, and significantly higher stretch in the fiber direction, was observed. These results provide additional insight into native tissue structure-function relationships, as well as new benchmarks for engineering functional AF tissue constructs.

  4. Effect of external stress on phase diagrams and dielectric properties of epitaxial ferroelectric thin films grown on orthorhombic substrates

    Institute of Scientific and Technical Information of China (English)

    L(U) Ye-gang; DENG Shui-feng; GONG Lun-jun; YANG Jian-tao

    2006-01-01

    A Landau-Ginsburg-Devonshire(LD)-type thermodynamic theory was used to describe the effect of external stress on phase diagrams and dielectric properties of epitaxial ferroelectric thin films grown on orthorhombic substrates which induce nonequally biaxial misfit strains in the films plane. The "misfit strain-external stress" and "external stress-temperature" phase diagrams were constructed for single-domain BaTiO3(BT) and PbTiO3(PT) thin films. It is shown that the external stress may lead to the rotation of the spontaneous polarization and a gradual change of its magnitude, which may result in phase transition. Nonequally biaxial misfit strains dependence of the stability of polarization states may be governed by external stress. At room temperature,stress-induced ferroelectric/paraelectric phase transition which occurs in film on cubic substrate does not take place in the ferroelectric thin film grown on orthorhombic substrate. It is also shown that the nonequally misfit strains in the film plane may lead to the appearance of new phases which do not form in films grown on cubic substrates under external stress. The dependence of the dielectric response on the external stress is also studied. It is shown that the dielectric constants of single-domain PT and BT films are very sensitive to the external stress under the given anisotropic misfit strains-temperature conditions. It presents theoretical evidence that the external stress and anisotropic misfit strains can be employed for improving the thin films physical properties.

  5. Effects of Interphase Modification and Biaxial Orientation on Dielectric Properties of Poly(ethylene terephthalate)/Poly(vinylidene fluoride-co-hexafluoropropylene) Multilayer Films.

    Science.gov (United States)

    Yin, Kezhen; Zhou, Zheng; Schuele, Donald E; Wolak, Mason; Zhu, Lei; Baer, Eric

    2016-06-01

    Recently, poly(vinylidene fluoride) (PVDF)-based multilayer films have demonstrated enhanced dielectric properties, combining high energy density and high dielectric breakdown strength from the component polymers. In this work, further enhanced dielectric properties were achieved through interface/interphase modulation and biaxial orientation for the poly(ethylene terephthalate)/poly(methyl methacrylate)/poly(vinylidene fluoride-co-hexafluoropropylene) [PET/PMMA/P(VDF-HFP)] three-component multilayer films. Because PMMA is miscible with P(VDF-HFP) and compatible with PET, the interfacial adhesion between PET and P(VDF-HFP) layers should be improved. Biaxial stretching of the as-extruded multilayer films induced formation of highly oriented fibrillar crystals in both P(VDF-HFP) and PET, resulting in improved dielectric properties with respect to the unstretched films. First, the parallel orientation of PVDF crystals reduced the dielectric loss from the αc relaxation in α crystals. Second, biaxial stretching constrained the amorphous phase in P(VDF-HFP) and thus the migrational loss from impurity ions was reduced. Third, biaxial stretching induced a significant amount of rigid amorphous phase in PET, further enhancing the breakdown strength of multilayer films. Due to the synergistic effects of improved interfacial adhesion and biaxial orientation, the PET/PMMA/P(VDF-HFP) 65-layer films with 8 vol % PMMA exhibited optimal dielectric properties with an energy density of 17.4 J/cm(3) at breakdown and the lowest dielectric loss. These three-component multilayer films are promising for future high-energy-density film capacitor applications. PMID:27163929

  6. Investigation of the interface characteristics of Y2O3/GaAs under biaxial strain, triaxial strain, and non-strain conditions

    Science.gov (United States)

    Shi, Li-Bin; Liu, Xu-Yang; Dong, Hai-Kuan

    2016-09-01

    We investigate the interface behaviors of Y2O3/GaAs under biaxial strain, triaxial strain, and non-strain conditions. This study is performed by first principles calculations based on density functional theory (DFT). First of all, the biaxial strain is realized by changing the lattice constants in ab plane. Averaged electrostatic potential (AEP) is aligned by establishing Y2O3 and GaAs (110) surfaces. The band offsets of Y2O3/GaAs interface under biaxial strain are investigated by generalized gradient approximation and Heyd-Scuseria-Ernzerhof (HSE) functionals. The interface under biaxial strain is suitable for the design of metal oxide semiconductor (MOS) devices because the valence band offsets (VBO) and conduction band offsets (CBO) are larger than 1 eV. Second, the triaxial strain is applied to Y2O3/GaAs interface by synchronously changing the lattice constants in a, b, and c axis. The band gaps of Y2O3 and GaAs under triaxial strain are investigated by HSE functional. We compare the VBO and CBO under triaxial strain with those under biaxial strain. Third, in the absence of lattice strain, the formation energies, charge state switching levels, and migration barriers of native defects in Y2O3 are assessed. We investigate how they will affect the MOS device performance. It is found that VO+2 and Oi-2 play a very dangerous role in MOS devices. Finally, a direct tunneling leakage current model is established. The model is used to analyze current and voltage characteristics of the metal/Y2O3/GaAs.

  7. Ion-beam assisted deposition of MgO with in situ RHEED monitoring to control Bi-axial texture

    Energy Technology Data Exchange (ETDEWEB)

    Arendt, P. N. (Paul N.); Foltyn, S. R. (Stephen R.); Jia, Quanxi; DePaula, R. F. (Raymond Felix); Dowden, P. C. (Paul C.); Kung, H. (Harriett); Holesinger, T. G. (Terry G.); Stan, L. (Liliana); Emmert, L. A. (Luke A.); Peterson, E. J. (Eric J.); Groves, J. R. (James R.)

    2001-01-01

    We have studied the growth of magnesium oxide using ion-beam assisted deposition (IBAD) to achieve (100) oriented, bi-axially textured films with low mosaic spread, for film thicknesses of 10 nm on silicon substrates. We have refined the process by using reflected high-energy electron diffraction (RHEED) to monitor the growth of IBAD MgO films and found that the diffracted intensity can be used to determine (and ultimately control) final in-plane texture of the film. Here we present results on our work to develop the use of real-time RHEED monitoring to deposit well-oriented IBAD MgO films. The results have been corroborated with extensive grazing-incidence X-ray diffraction (GID). Results of these analyses have allowed us to deposit films on metallic substrates with in-plane mosaic spread less than 7{sup o}.

  8. Monte Carlo investigation of critical properties of the Landau point of a biaxial liquid-crystal system.

    Science.gov (United States)

    Ghoshal, Nababrata; Shabnam, Sabana; DasGupta, Sudeshna; Roy, Soumen Kumar

    2016-05-01

    Extensive Monte Carlo simulations are performed to investigate the critical properties of a special singular point usually known as the Landau point. The singular behavior is studied in the case when the order parameter is a tensor of rank 2. Such an order parameter is associated with a nematic-liquid-crystal phase. A three-dimensional lattice dispersion model that exhibits a direct biaxial nematic-to-isotropic phase transition at the Landau point is thus chosen for the present study. Finite-size scaling and cumulant methods are used to obtain precise values of the critical exponent ν=0.713(4), the ratio γ/ν=1.85(1), and the fourth-order critical Binder cumulant U^{*}=0.6360(1). Estimated values of the exponents are in good agreement with renormalization-group predictions.

  9. Uniaxial and biaxial ratchetting study of SA333 Gr.6 steel at room temperature

    International Nuclear Information System (INIS)

    The phenomenon of ratchetting is defined as constant accumulation of plastic strain or deformation under combined steady state and cyclic loading. It can reduce the fatigue life or can cause failure of piping components or systems subjected to seismic or other cyclic loads. The uniaxial ratchetting characteristics of SA333 Gr.6 steel have been investigated at room temperature in the present paper. The specimens were subjected to cyclic axial stress with a constant mean stress of 200 MPa and a varying amplitude stress of 149, 174, 199 and 224 MPa. Tests were also performed on 203.2 mm, Sch 80, SA333 Gr. 6 carbon steel straight pipe. The pipe was subjected to a constant internal pressure of 18 MPa and a cyclic bending load. The effects of amplitude of load on the rate of ratchetting have also been investigated in the present paper. The uniaxial experiments showed that specimens exhibited shakedown at low stress amplitude after some strain accumulation. However, specimens experienced continuous ratchetting at higher stress amplitudes with no shakedown before failure. Ovalization of the pipe cross-section was observed when the pipe was subjected to constant internal pressure and cyclic point load. Local bulging was observed at higher loading. The pipe did not show any shakedown behaviour for the given cycles of loading and exhibited continuous ratchetting under the varying amplitude loading

  10. Failure mechanics of fiber composite notched charpy specimens. [stress analysis

    Science.gov (United States)

    Chamis, C. C.

    1976-01-01

    A finite element stress analysis was performed to determine the stress variation in the vicinity of the notch and far field of fiber composites Charpy specimens (ASTM Standard). NASTRAN was used for the finite element analysis assuming linear behavior and equivalent static load. The unidirectional composites investigated ranged from Thornel 75 Epoxy to S-Glass/Epoxy with the fiber direction parallel to the long dimension of the specimen. The results indicate a biaxial stress state exists in (1) the notch vicinity which is dominated by transverse tensile and interlaminar shear and (2) near the load application point which is dominated by transverse compression and interlaminar shear. The results also lead to the postulation of hypotheses for the predominant failure modes, the fracture initiation, and the fracture process. Finally, the results indicate that the notched Charpy test specimen is not suitable for assessing the impact resistance of nonmetallic fiber composites directly.

  11. Childhood Stress

    Science.gov (United States)

    ... 5 Things to Know About Zika & Pregnancy Childhood Stress KidsHealth > For Parents > Childhood Stress Print A A ... and feel stress to some degree. Sources of Stress Stress is a function of the demands placed ...

  12. Stress Management

    Science.gov (United States)

    ... Awards Healthy Workplace Food and Beverage Toolkit Stress Management Banner 1 - To Stress or Not to Stress - ... Decide But We Can Help What Is Stress Management? Banner 2 - Stress Continuum Graphic Banner Live life ...

  13. Ferromagnetic resonance in thin films submitted to multiaxial stress state: application of the uniaxial equivalent stress concept and experimental validation

    Science.gov (United States)

    Gueye, M.; Zighem, F.; Belmeguenai, M.; Gabor, M.; Tiusan, C.; Faurie, D.

    2016-07-01

    In this paper a unique expression of the anisotropy field induced by any multiaxial stress state in a magnetic thin film and probed by ferromagnetic resonance is derived. This analytical development has been made using the uniaxial equivalent stress concept, for which correspondances between definitions given by different authors in the literature is found. The proposed model for the anisotropy field has been applied to \\text{C}{{\\text{o}}2}\\text{FeAl} thin films (25 nm) stressed both by piezoelectric actuation (non-equi-biaxial) or by bending tests (uniaxial) and measured with a broadband ferromagnetic resonance technique. The overall exprimental data can be easily plotted on a unique graph from which the magnetostriction coefficient has been estimated.

  14. Mechanics of Stabbing: Biaxial Measurement of Knife Stab Penetration of Skin Simulant

    OpenAIRE

    Gilchrist, Michael,; Keenan, Stephen; Curtis, Michael; Cassidy, Mary; Byrne, Greg; Destrade, Michel

    2008-01-01

    International audience; In medicolegal situations, the consequences of a stabbing incident are described in terms that are qualitative without being quantitative. Here, the mechanical variables involved in knife-tissue penetration events are used to determine the parameters needed to be controlled in a measurement device. They include knife geometry, in-plane mechanical stress state of skin, angle and speed of knife penetration, and underlying fascia. Four household knives with different geom...

  15. Biaxial order and a rotation of the minor director in the nematic phase of an organo-siloxane tetrapode by the electric field

    Science.gov (United States)

    Merkel, K.; Nagaraj, M.; Kocot, A.; Kohlmeier, A.; Mehl, G. H.; Vij, J. K.

    2012-03-01

    Biaxiality in the nematic phase for a liquid crystalline tetrapode made up of organo-siloxanes mesogens is investigated using polarized infrared spectroscopy. An ordering of the minor director for the homeotropically aligned sample is found to depend on the amplitude of the in-plane electric field. On increasing the in-plane electric field, the minor director, lying initially along the rubbing direction, rotates to the direction of the applied field. The scalar order parameters of the second rank tensor are found to depend significantly on the strength of the electric field. A most significant increase is found in the nematic order parameter and in the parameter that characterizes the phase biaxiality.

  16. High critical current density superconducting tapes by epitaxial deposition of YBa2Cu3Ox thick films on biaxially textured metals

    International Nuclear Information System (INIS)

    A method to obtain long lengths of flexible, biaxially oriented substrates with smooth, chemically compatible surfaces for epitaxial growth of high-temperature superconductors is reported. The technique uses well established, industrially scalable, thermomechanical processes to impart a strong biaxial texture to a base metal. This is followed by vapor deposition of epitaxial buffer layers (metal and/or ceramic) to yield chemically compatible surfaces. Epitaxial YBa2Cu3Ox films grown on such substrates have critical current densities exceeding 105 A/cm2 at 77 K in zero field and have field dependencies similar to epitaxial films on single crystal ceramic substrates. Deposited conductors made using this technique offer a potential route for the fabrication of long lengths of high-Jc wire capable of carrying high currents in high magnetic fields and at elevated temperatures. copyright 1996 American Institute of Physics

  17. Nonorthogonal {{sp}}^{3}{{d}}^{5} tight-binding parameterization of single-layer phosphorene under biaxial strain and application to FETs

    Science.gov (United States)

    Lee, Jaehyun; Seo, Jumbeom; Oh, Jung Hyun; Shin, Mincheol

    2016-06-01

    This paper presents a new set of {{sp}}3{{d}}5 tight-binding (TB) parameters for single-layer phosphorene within the Naval Research Laboratory (NRL) scheme. For this, we develop the numerical algorithm to find the NRL TB parameters fitted to ab initio results. It is shown that the proposed NRL TB parameters successfully reproduce the band structure of a single-layer phosphorene, and even under biaxial or uniaxial strain, they appropriately describe the effects, such as modification of anisotropic effective masses and band gap. Via the top-of-the-barrier model, we also investigate the performance of single-layer phosphorene FETs under biaxial strain with the NRL TB Hamiltonian and find that the results are well in accordance with those of previous studies.

  18. Spin-to-orbital angular momentum conversion for Bessel beams propagating along the optical axes of homogeneous uniaxial and biaxial crystals

    International Nuclear Information System (INIS)

    A study is made of the dynamics of the spin-to-orbital angular momentum conversion for zero-order and high order circularly polarized Bessel beams propagating along the optical axes of homogeneous uniaxial and biaxial crystals. Implementation of Bessel beams and a slab of homogeneous uniaxial crystal allow one to realize a highly efficient (about 100%) optical process in which the direct conversion of the optical angular momentum from the spin form to the orbital form takes place. It is shown that only in a biaxial crystal is there freedom from compensation of spin and orbital angular momentum exchanges with matter and, as a result, the optical torque emerges, which influences the plate. (paper)

  19. High-performance poly-Si thin film transistors with highly biaxially oriented poly-Si thin films using double line beam continuous-wave laser lateral crystallization

    Science.gov (United States)

    Yamano, Masayuki; Kuroki, Shin-Ichiro; Sato, Tadashi; Kotani, Koji

    2014-01-01

    Highly biaxially oriented poly-Si thin films were formed by double-line beam continuous-wave laser lateral crystallization (DLB-CLC). The crystallinities of the DLB-CLC poly-Si thin films were (110), (111), and (211) for the laser scan, transverse, and surface directions, respectively, and an energetically stable Σ3 grain boundary was observed to be dominant. All silicon grains were elongated in the laser scan direction and one-dimensionally very large silicon grains with lengths of more than 100 µm were fabricated. Using these biaxially oriented polycrystalline silicon (poly-Si) films, low-temperature poly-Si TFTs (LTPS-TFTs) were fabricated at low temperatures (≦550 °C) by a metal gate self-aligned process. As a result, a TFT with a high electron field effect mobility of μFE = 450 cm2 V-1 s-1 in a linear region was realized.

  20. Lattice strain development in Inconel-690 under bi-axial compression and tension

    Science.gov (United States)

    Toda, Rebecca Midori

    Nuclear reactor steam generator tubes, manufactured from Nickel alloys such as Inconel 690 (INC690), are potentially susceptible to failure by Stress Corrosion Cracking where crack initiation may be exacerbated by internal stress fields. A more comprehensive understanding of this potential failure mechanism was gained via an exploration of a model of INC690.s behaviour under Constrained loading conditions in compression and tension. An Elasto-Plastic Self-Consistent (EPSC) model was used to predict the lattice stresses and strains resulting from Constrained loading in INC690 for four crystallographic planes. The internal strain fields generated under such conditions were shown to be markedly different from those developed under Uniaxial loading. Finite Element Modeling was used to design tensile and compression samples as well as a testing rig that would allow the application of a compressive load along one axis of the specimen with simultaneous constraint along another and free-deformation along the third. Lattice strain measurements were done for both compressive and tensile loading using Time-Of-Flight neutron diffraction. The predicted and experimental values showed reasonable agreement; mainly in terms of crystallographic plane interaction and behaviour. Iterative computer modeling was used to achieve a more realistic depiction of the lattice strains developed. This research allowed for an extension on the Uniaxial findings by examining the material's behaviour under more complex loading that better approximates steam generator tube operating conditions.

  1. Increasing the band gap of FeS{sub 2} by alloying with Zn and applying biaxial strain: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Pin [School of Material Science and Engineering, State Key Laboratory of Solidification Processing, Northwestern Polytechnic University, 127 YouYi Western Road, Xi’an, Shaanxi 710072 (China); Beijing Computational Science Research Center, Beijing 100084 (China); Fan, Xiao-Li, E-mail: xlfan@nwpu.edu.cn [School of Material Science and Engineering, State Key Laboratory of Solidification Processing, Northwestern Polytechnic University, 127 YouYi Western Road, Xi’an, Shaanxi 710072 (China); Beijing Computational Science Research Center, Beijing 100084 (China); Zhang, Han; Fang, Xiaoliang [School of Material Science and Engineering, State Key Laboratory of Solidification Processing, Northwestern Polytechnic University, 127 YouYi Western Road, Xi’an, Shaanxi 710072 (China); Liu, Li-Min, E-mail: limin.liu@csrc.ac.cn [Beijing Computational Science Research Center, Beijing 100084 (China); Chengdu Green Energy and Green Manufacturing Technology R& D Center, Chengdu, Sichuan 610207 (China)

    2015-04-25

    Highlights: • The combined effect of doping and biaxial strain on the physical properties of FeS{sub 2} was studied. • The band gap of FeS{sub 2} is widen by ∼0.29 eV under 5% tensile strain with Zn alloying at 6.25% concentration. • Alloying with Zn and biaxial tensile strain effectively improve the electronic and optical properties of FeS{sub 2}. - Abstract: The combined effect of alloying and biaxial strain on atomic structure, as well as electronic and optical properties of FeS{sub 2} was first examined by the first-principles calculation. By allaying with Zn, our results show that the band gap of Fe{sub 1−x}Zn{sub x}S{sub 2} alloy increases firstly and then decreases with increasing Zn concentration, the maximum enlargement of band gap is ∼0.1 eV. The left shift of the absorption threshold enhances the overall optical absorptivity. By imposing biaxial strain on the Zn-doped FeS{sub 2}, the band gap decreases under compressive strain, but increases from 0.95 eV to 1.14 eV under 5% tensile strain. More specially, strain widens the band gap of Zn-doped FeS{sub 2} by ∼0.19 eV, and the overall optical absorptivity is further enhanced by the combination of strain and Zn-doping. With the increase of the band gap by ∼0.29 eV and the high optical absorptivity, FeS{sub 2} is a more promising material for photovoltaic applications.

  2. Increasing the band gap of FeS2 by alloying with Zn and applying biaxial strain: A first-principles study

    International Nuclear Information System (INIS)

    Highlights: • The combined effect of doping and biaxial strain on the physical properties of FeS2 was studied. • The band gap of FeS2 is widen by ∼0.29 eV under 5% tensile strain with Zn alloying at 6.25% concentration. • Alloying with Zn and biaxial tensile strain effectively improve the electronic and optical properties of FeS2. - Abstract: The combined effect of alloying and biaxial strain on atomic structure, as well as electronic and optical properties of FeS2 was first examined by the first-principles calculation. By allaying with Zn, our results show that the band gap of Fe1−xZnxS2 alloy increases firstly and then decreases with increasing Zn concentration, the maximum enlargement of band gap is ∼0.1 eV. The left shift of the absorption threshold enhances the overall optical absorptivity. By imposing biaxial strain on the Zn-doped FeS2, the band gap decreases under compressive strain, but increases from 0.95 eV to 1.14 eV under 5% tensile strain. More specially, strain widens the band gap of Zn-doped FeS2 by ∼0.19 eV, and the overall optical absorptivity is further enhanced by the combination of strain and Zn-doping. With the increase of the band gap by ∼0.29 eV and the high optical absorptivity, FeS2 is a more promising material for photovoltaic applications

  3. The biaxial nonlinear crystal BiB3O6 as a polarization entangled photon source using non-collinear type-II parametric down-conversion

    OpenAIRE

    Halevy, A.; Megidish, E.; Dovrat, L.; Eisenberg, H. S.; De Becker, P; Bohatý, L.

    2011-01-01

    We describe the full characterization of the biaxial nonlinear crystal BiB3O6 (BiBO) as a polarization entangled photon source using non-collinear type-II parametric down-conversion. We consider the relevant parameters for crystal design, such as cutting angles, polarization of the photons, effective nonlinearity, spatial and temporal walk-offs, crystal thickness and the effect of the pump laser bandwidth. Experimental results showing entanglement generation with high rates and a comparison t...

  4. The critical state of an inclined layer in a sheet specimen with negative loading biaxiality coefficient

    OpenAIRE

    DILMAN V.L.; DHEYAB A.N.

    2016-01-01

    We study conditions for the loss of stability in a plastic deformation of a layer of weaker material in a sheet specimen. The layer is not collinear with the exterior forces acting in the sheet plane, which are orthogonal to each other and have opposite signs. The parameters of the problem are: the angle between the layer and the direction of exterior forces; the ratio of stresses due to exterior forces; the ratio of strengths of the layer material and the main material of the sheet specimen;...

  5. Evaluation of multiaxial stress in textured cubic films by x-ray diffraction

    Institute of Scientific and Technical Information of China (English)

    Zhang Jian-Min; Xu Ke-Wei

    2005-01-01

    X-ray diffraction is used extensively to determine the residual stress in bulk or thin film materials on the assumptions that the material is composed of fine crystals with random orientation and the stress state is biaxial and homogeneous through the x-ray penetrating region. The stress is calculated from the gradient of ε~ sin2 ψ linear relation. But the method cannot be used in textured films due to nonlinear relation. In this paper, a novel method is proposed for measuring the multiaxial stresses in cubic films with any [hkl] fibre texture. As an example, a detailed analysis is given for measuring three-dimensional stresses in FCC films with [111] fibre texture.

  6. Residual stress in AlN films grown on sapphire substrates by molecular beam epitaxy

    Science.gov (United States)

    Rong, Xin; Wang, Xinqiang; Chen, Guang; Pan, Jianhai; Wang, Ping; Liu, Huapeng; Xu, Fujun; Tan, Pingheng; Shen, Bo

    2016-05-01

    Residual stress in AlN films grown by molecular beam epitaxy (MBE) has been studied by Raman scattering spectroscopy. A strain-free Raman frequency and a biaxial stress coefficient for E2(high) mode are experimentally determined to be 657.8 ± 0.3 cm-1 and 2.4 ± 0.2 cm-1 / GPa, respectively. By using these parameters, the residual stress of a series of AlN layers grown under different buffer layer conditions has been investigated. The residual compressive stress is found to be obviously decreased by increasing the Al/N beam flux ratio of the buffer layer, indicating the generation of tensile stress due to stronger coalescence of AlN grains, as also confirmed by the in-situ reflection high energy electron diffraction (RHEED) monitoring observation. The stronger coalescence does lead to improved quality of AlN films as expected.

  7. Strain mapping near a triple junction in strained Ni-based alloy using EBSD and biaxial nanogauges

    Energy Technology Data Exchange (ETDEWEB)

    Clair, A. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47870, 21078 Dijon Cedex (France); Foucault, M.; Calonne, O. [Areva ANP, Centre Technique Departement Corrosion-Chimie, 30 Bd de l' industrie, BP 181, 71205 Le Creusot (France); Lacroute, Y.; Markey, L.; Salazar, M.; Vignal, V. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47870, 21078 Dijon Cedex (France); Finot, E., E-mail: Eric.Finot@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47870, 21078 Dijon Cedex (France)

    2011-05-15

    Research highlights: > Surface strains measured using nanogauge were compared to the texture obtained by EBSD. > Statistics of the principal strain discern the grains according to the Schmid factor. > Strain hotspots were localized near a triple junction of alloy 600 under tensile loading. > Asymetrical profile of the GB strains is a criterion for surface cracking initiation. - Abstract: A key element for analyzing the crack initiation in strained polycrystalline alloys is the local quantification of the surface strain distribution according to the grain texture. Using electron backscattered diffraction, the local microstructure was determined to both localize a triple junction and deduce the local Schmid factors. Kernel average misorientation (KAM) was also used to map the areas of defect concentration. The maximum principal strain and the in-plane shear strain were quantified using the biaxial nanogauge. Distortions of the array of nanodots used as spot markers were analyzed near the triple junction. The crystallographic orientation and the surface strain were then investigated both statistically for each grain and locally at the grain boundaries. The superimposition of microstructure and strain maps allows the high strain gradient (reaching 3-fold the applied strain) to be localized at preferential grain boundaries near the triple junction. The Schmid factors and the KAM were compared to the maximum principal strain and the in-plane shear strain respectively. The polycrystalline deformation was attributable first to the rotation of some grains, followed by the elongation of all grains along their preferential activated slip systems.

  8. Fabrication of High Current YBa2Cu3O7-y Coated Conductors Using Rolling-Assisted Biaxially Textured Substrates

    International Nuclear Information System (INIS)

    High critical current YBa2Cu3O7-y (referred to as YBCO) coated conductors were fabricated with a layer sequence of YBCO/YSZ/CeO2/Ni. The cube (100) texture in the starting Ni substrates was obtained by cold rolling followed by recrystallization. A thin CeO2 (Cerium Oxide) layer with a thickness of 100-200 was grown epitaxially on the biaxially textured-Ni substrates using an e-beam evaporation technique. This was followed by the growth of a thick (2 film had a dense microstructure. The microstructure of the e-beam YSZ film was porous whereas the sputtered YSZ film was dense. The YBCO films were grown by pulsed laser deposition on both e-beam and sputtered YSZ layers. A transport critical current density of 1 x l06 A/cm2 at 77 K was obtained for 0.8 m thick YBCO Rims on both YSZ surfaces in zero field. To demonstrate the quality and compatibility of the e-beam CeO2 layers; YBCO films were also grown on CeO2-buffered YSZ (100) single crystal substrates using e-beam co-evaporated Y-BaF2-Cu precursors followed by a post-annealing process. A transport critical current density of over 1 x lO6A/cm2 at 77 K was obtained on a 0.3 m thick YBCO film in zero field

  9. Vector hysteresis measurements of not oriented grain SiFe steels by a biaxial hall sensors array

    Science.gov (United States)

    Cardelli, E.; Faba, A.

    2014-02-01

    This work discusses the vector measurement of the effective magnetic field inside a not oriented grain SiFe steel sample, taking into account the effect of the demagnetizing field. We propose an array of biaxial Hall sensors, placed up to the sample surface. The calibration of the system and a suitable extrapolation data strongly reduce the uncertainties of the direct measurement and provide an accurate evaluation of the magnetic field inside the material sample. Although the approach proposed can be also used for industrial frequencies, 50-60 Hz or more, the analysis is limited here to the static case, because we are mainly interested in static magnetic measurements. These measurements are especially useful for the vector characterization of soft magnetic materials and, in particular, for the identification and the experimental validation of vector hysteresis models. The experimental analysis presented in the paper deals with commercial not oriented grain SiFe steels. Experimental data about hysteresis loops and static power losses are given.

  10. Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression.

    Science.gov (United States)

    Sirry, Mazin S; Butler, J Ryan; Patnaik, Sourav S; Brazile, Bryn; Bertucci, Robbin; Claude, Andrew; McLaughlin, Ron; Davies, Neil H; Liao, Jun; Franz, Thomas

    2016-10-01

    Understanding the passive mechanical properties of infarcted tissue at different healing stages is essential to explore the emerging biomaterial injection-based therapy for myocardial infarction (MI). Although rats have been widely used as animal models in such investigations, the data in literature that quantify the passive mechanical properties of rat heart infarcts is very limited. MI was induced in rats and hearts were harvested immediately (0 day), 7, 14 and 28 days after infarction onset. Left ventricle anterioapical samples were cut and underwent equibiaxial and non equibiaxial tension followed by uniaxial compression mechanical tests. Histological analysis was conducted to confirm MI and to quantify the size of the induced infarcts. Infarcts maintained anisotropy and the nonlinear biaxial and compressive mechanical behaviour throughout the healing phases with the circumferential direction being stiffer than the longitudinal direction. Mechanical coupling was observed between the two axes in all infarct groups. The 0, 7, 14 and 28 days infarcts showed 438, 693, 1048 and 1218kPa circumferential tensile moduli. The 28 day infarct group showed a significantly higher compressive modulus compared to the other infarct groups (p=0.0060, 0.0293, and 0.0268 for 0, 7 and 14 days groups). Collagen fibres were found to align in a preferred direction for all infarct groups supporting the observed mechanical anisotropy. The presented data are useful for developing material models for healing infarcts and for setting a baseline for future assessment of emerging mechanical-based MI therapies. PMID:27434651

  11. Partial hydrophilic modification of biaxially oriented polypropylene film by an atmospheric pressure plasma jet with the allylamine monomer

    Science.gov (United States)

    Chen, W. X.; Yu, J. S.; Hu, W.; Chen, G. L.

    2016-11-01

    In this paper, the partial modification of the biaxially oriented polypropylene (BOPP) film for potential biological and packaging applications was achieved via hydrophilic modification using atmospheric pressure plasma jet (APPJ). In the APPJ system, the allylamine (ALA) monomer was polymerized on the BOPP surface by either the Ar/O2 or the He/O2 plasma. The results showed that plasmatic modification created many micro/nano sized holes on the BOPP film, which increased the surface roughness dramatically and the increased roughness enhanced the combining intensity between the BOPP film and the ALA polymer. However, such a plasmatic modification increased the water vapor permeability. The FTIR and XPS characterizations showed that the amine groups were grafted onto the BOPP film, and the contact angle of the BOPP film decreases from 98.5° to 8°. Compared with the BOPP films treated by the Ar or He plasma, the barrier property of the modified BOPP film increased significantly when the ALA polymer was incorporated. The bio-affinity/toxicity of ALA polymer was illustrated by the attachment of the cultured SMMC-7721 hepatoma cells on the modified BOPP film. The significant enhancement in the cell density indicated that modified BOPP film was highly bio-compatible and non-toxic, especially treated with the Ar/O2/ALA plasma.

  12. Wrinkle-to-fold transition in soft layers under equi-biaxial strain: A weakly nonlinear analysis

    Science.gov (United States)

    Ciarletta, P.

    2014-12-01

    Soft materials can experience a mechanical instability when subjected to a finite compression, developing wrinkles which may eventually evolve into folds or creases. The possibility to control the wrinkling network morphology has recently found several applications in many developing fields, such as scaffolds for biomaterials, stretchable electronics and surface micro-fabrication. Albeit much is known of the pattern initiation at the linear stability order, the nonlinear effects driving the pattern selection in soft materials are still unknown. This work aims at investigating the nature of the elastic bifurcation undertaken by a growing soft layer subjected to a equi-biaxial strain. Considering a skin effect at the free surface, the instability thresholds are found to be controlled by a characteristic length, defined by the ratio between capillary energy and bulk elasticity. For the first time, a weakly nonlinear analysis of the wrinkling instability is performed here using the multiple-scale perturbation method applied to the incremental theory in finite elasticity. The Ginzburg-Landau equations are derived for different superposing linear modes. This study proves that a subcritical pitchfork bifurcation drives the observed wrinkle-to-fold transition in swelling gels experiments, favoring the emergence of hexagonal creased patterns, albeit quasi-hexagonal patterns might later emerge because of an expected symmetry break. Moreover, if the surface energy is somewhat comparable to the bulk elastic energy, it has the same stabilizing effect as for fluid instabilities, driving the formation of stable wrinkles, as observed in elastic bi-layered materials.

  13. Molecular ordering in a biaxial smectic-A phase studied by scanning transmission X-ray microscopy (STXM).

    Science.gov (United States)

    Kaznacheev, Konstantin; Hegmann, Torsten

    2007-04-14

    Results of STXM investigations of a binary mixture (-TNF = 2 : 1; SmA(b) 140 M 180 Iso) known to form a SmA(b) phase [T. Hegmann, J. Kain, S. Diele, G. Pelzl and C. Tschierske, Angew. Chem. Int. Ed., 2001, 40, 887] are presented. Near edge X-ray absorption fine spectra (NEXAFS) of the -TNF board-like aggregates, in particular the intensity of the low energy peaks associated with aromatic ring pi* orbitals (284.5-286.5 eV), show that the molecular plane of these aggregates is very sensitive to the relative orientation of electric field vector E of linearly polarized light, which is used to determine the molecular orientation in the LC phase. The observed strong in-plane dichroic signal suggests the predominant orientation of the -TNF aggregates to be along the smectic layer normal as well as long-range ordering of the in-plane molecular orientation (biaxiality). Orientational maps derived from series of measurements at different sample rotation angles around the specimen normal clearly show a Schlieren-type texture, and permit a detailed examination of exclusive +/-(1/2) disclination theoretically predicted for the SmA(b) phase.

  14. The diverse electronic properties of C4N3 monolayer under biaxial compressive strain: a theoretical study

    Science.gov (United States)

    Wu, Haiping; Liu, Yuzhen; Kan, Erjun; Ma, Yanming; Xu, Wenjie; Li, Jie; Yan, Meichen; Lu, Ruifeng; Wei, Jianfeng; Qian, Yan

    2016-07-01

    Because of the observation of half-metallicity in graphitic carbon nitride C4N3 (g-C4N3), extensive research has recently been focused on this compound. Using density-functional calculations, herein diverse electronic properties of g-C4N3 were engineered by applying biaxial compressive strain. The calculated results demonstrate that g-C4N3 preserves ferromagnetic half-metallicity when the strain is lower than  ‑2%, accompanied by a decrease of the half-metallic gap. When the compressive strain ranges from  ‑5 to  ‑3%, the compound turns into nonmagnetic metal. By increasing the strain on the end, it becomes a nonmagnetic semiconductor. Further investigations show that all nonmagnetic semiconductors possess a direct band gap with a value of around 1.6 eV. This fact indicates that g-C4N3 can be applied in spintronic or photovoltaic fields under a strain environment.

  15. Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression.

    Science.gov (United States)

    Sirry, Mazin S; Butler, J Ryan; Patnaik, Sourav S; Brazile, Bryn; Bertucci, Robbin; Claude, Andrew; McLaughlin, Ron; Davies, Neil H; Liao, Jun; Franz, Thomas

    2016-10-01

    Understanding the passive mechanical properties of infarcted tissue at different healing stages is essential to explore the emerging biomaterial injection-based therapy for myocardial infarction (MI). Although rats have been widely used as animal models in such investigations, the data in literature that quantify the passive mechanical properties of rat heart infarcts is very limited. MI was induced in rats and hearts were harvested immediately (0 day), 7, 14 and 28 days after infarction onset. Left ventricle anterioapical samples were cut and underwent equibiaxial and non equibiaxial tension followed by uniaxial compression mechanical tests. Histological analysis was conducted to confirm MI and to quantify the size of the induced infarcts. Infarcts maintained anisotropy and the nonlinear biaxial and compressive mechanical behaviour throughout the healing phases with the circumferential direction being stiffer than the longitudinal direction. Mechanical coupling was observed between the two axes in all infarct groups. The 0, 7, 14 and 28 days infarcts showed 438, 693, 1048 and 1218kPa circumferential tensile moduli. The 28 day infarct group showed a significantly higher compressive modulus compared to the other infarct groups (p=0.0060, 0.0293, and 0.0268 for 0, 7 and 14 days groups). Collagen fibres were found to align in a preferred direction for all infarct groups supporting the observed mechanical anisotropy. The presented data are useful for developing material models for healing infarcts and for setting a baseline for future assessment of emerging mechanical-based MI therapies.

  16. Mechanics of Stabbing: Biaxial Measurement of Knife Stab Penetration of Skin Simulant

    CERN Document Server

    Gilchrist, Michael D; Curtis, Michael; Cassidy, Mary; Byrne, Greg; Destrade, Michel; 10.1016/j.forsciint.2007.10.010

    2008-01-01

    In medicolegal situations, the consequences of a stabbing incident are described in terms that are qualitative without being quantitative. Here, the mechanical variables involved in knife-tissue penetration events are used to determine the parameters needed to be controlled in a measurement device. They include knife geometry, in-plane mechanical stress state of skin, angle and speed of knife penetration, and underlying fascia. Four household knives with different geometries were used. Synthetic materials were used to simulate the response of skin, fat and cartilage: polyurethane, foam, and ballistic soap, respectively. The force and energy applied by the blade and the skin displacement were used to identify skin penetration. The skin tension is shown to have a direct effect on the force and energy for knife penetration and on the depth of displacement of the simulant prior to penetration: larger levels of in-plane tension in the skin are associated with lower penetration forces, energies and displacements. L...

  17. A criterion for high-cycle fatigue life and fatigue limit prediction in biaxial loading conditions

    Science.gov (United States)

    Pejkowski, Łukasz; Skibicki, Dariusz

    2016-08-01

    This paper presents a criterion for high-cycle fatigue life and fatigue strength estimation under periodic proportional and non-proportional cyclic loading. The criterion is based on the mean and maximum values of the second invariant of the stress deviator. Important elements of the criterion are: function of the non-proportionality of fatigue loading and the materials parameter that expresses the materials sensitivity to non-proportional loading. The methods for the materials parameters determination uses three S-N curves: tension-compression, torsion, and any non-proportional loading proposed. The criterion has been verified using experimental data, and the results are included in the paper. These results should be considered as promising. The paper also includes a proposal for multiaxial fatigue models classification due to the approach for the non-proportionality of loading.

  18. Manage Stress

    Science.gov (United States)

    ... Manage Stress Print This Topic En español Manage Stress Browse Sections The Basics Overview Signs and Health ... and Health Effects What are the signs of stress? When people are under stress, they may feel: ...

  19. 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...... θ has been chosen in order to obtain local multiaxial stress states in the off-axis plies similar to those in previous studies for biaxially loaded tubes. Results concerning damage initiation and growth for these two specimen configurations are shown to be consistent for similar local multiaxial...

  20. Evaluation of biaxial flexural strength and modulus of filled and unfilled adhesive systems = Avaliação da resistência flexural biaxial e módulo de flexão de sistemas adesivos

    Directory of Open Access Journals (Sweden)

    Liberti, Michele Santana

    2009-01-01

    Full Text Available Objetivo: O objetivo deste estudo foi avaliar a resistência flexural e o módulo de flexão de dois sistemas adesivos, através de ensaio de resistência flexural biaxial. Metodologia: Os adesivos (Pentron Clinical Technologies estudados foram: Bond 1 (B1 e NanoBond (NB. Treze discos de cada adesivo foram preparados com dimensões aproximadas de 6,1 mm de diâmetro e 0,6 mm de espessura. Os discos de adesivos foram confeccionados utilizando-se moldes de teflon e fotopolimerizados com aparelho XL 3000 (3M ESPE. Após armazenamento por 10 dias, os discos foram testados em máquina universal de ensaio (Instron 5844, com velocidade de 1,27 mm/min. Os dados foram submetidos à análise de variância (1 fator ao nível de significância de 0,05. Resultados: Os valores médios (±DP de resistência flexural para os adesivos foram (em MPa: B1- 89,7±7,6 e NB- 131,1±9,5. Os valores médios de módulo flexural (±DP foram (em MPa: B1- 1999,9±258,4 e NB- 2314,5±271,0. Conclusão: O adesivo contendo partículas de carga (NB mostrou maiores valores de resistência flexural e módulo de flexão que o adesivo B1

  1. Effect of Ceramic Surface Treatments After Machine Grinding on the Biaxial Flexural Strength of Different CAD/CAM Dental Ceramics

    Science.gov (United States)

    Bagheri, Hossein; Aghajani, Farzaneh

    2015-01-01

    Objectives: This study aimed to evaluate the effect of different ceramic surface treatments after machining grinding on the biaxial flexural strength (BFS) of machinable dental ceramics with different crystalline phases. Materials and Methods: Disk-shape specimens (10mm in diameter and 1.3mm in thickness) of machinable ceramic cores (two silica-based and one zirconia-based ceramics) were prepared. Each type of the ceramic surfaces was then randomly treated (n=15) with different treatments as follows: 1) machined finish as control, 2) machined finish and sandblasting with alumina, and 3) machined finish and hydrofluoric acid etching for the leucite and lithium disilicate-based ceramics, and for the zirconia; 1) machined finish and post-sintered as control, 2) machined finish, post-sintered, and sandblasting, and 3) machined finish, post-sintered, and Nd;YAG laser irradiation. The BFS were measured in a universal testing machine. Data based were analyzed by ANOVA and Tukey’s multiple comparisons post-hoc test (α=0.05). Results: The mean BFS of machined finish only surfaces for leucite ceramic was significantly higher than that of sandblasted (P=0.001) and acid etched surfaces (P=0.005). A significantly lower BFS was found after sandblasting for lithium disilicate compared with that of other groups (P<0.05). Sandblasting significantly increased the BFS for the zirconia (P<0.05), but the BFS was significantly decreased after laser irradiation (P<0.05). Conclusions: The BFS of the machinable ceramics was affected by the type of ceramic material and surface treatment method. Sandblasting with alumina was detrimental to the strength of only silica-based ceramics. Nd:YAG laser irradiation may lead to substantial strength degradation of zirconia. PMID:27148372

  2. Biaxial Flexural Strength of High-Viscosity Glass-Ionomer Cements Heat-Cured with an LED Lamp during Setting

    Directory of Open Access Journals (Sweden)

    Gustavo Fabián Molina

    2013-01-01

    Full Text Available Adding heat to glass ionomers during setting might improve mechanical properties. The aim was to compare the biaxial flexural strength (BFS between and within four glass ionomers, by time of exposure to a high-intensity LED light-curing unit. Materials and methods. Samples of Fuji 9 Gold Label, Ketac Molar Easymix, ChemFil Rock, and the EQUIA system were divided into three treatment groups (n=30: without heating (Group 1, heated with LED lamp of 1400 mW/cm2 for 30 s while setting (Group 2, and heated with LED lamp of 1400 mW/cm2 for 60 s while setting (Group 3. Samples were stored for 48 hours in distilled water at 37°C until tested. BFS was tested, using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed, using ANOVA test with the Bonferroni correction (α=0.05. Heating the glass-ionomer cements with an LED curing light of 1400 mW/cm2 during setting for 30 s increased the BFS value of all GICs. No statistically significant difference in mean BFS scores was found between the EQUIA system and ChemFil Rock at 30 s and 60 s. The mean BFS value was statistically significantly higher for the EQUIA system and ChemFil Rock than for Fuji 9 Gold Label and Ketac Molar Easymix at all exposure times.

  3. Biaxial bending of slender HSC columns and tubes filled with concrete under short- and long-term loads: I Theory

    Directory of Open Access Journals (Sweden)

    Jose A. Rodríguez-Gutiérrez

    2014-07-01

    Full Text Available An analytical method that calculates both the short- and long-term response of slender columns made of high-strength concrete (HSC and tubes filled with concrete with generalized end conditions and subjected to transverse loads along the span and axial load at the ends (causing a single or double curvature under uniaxial or biaxial bending is presented. The proposed method, which is an extension of a method previously developed by the authors, is capable of predicting not only the complete load-rotation and load-deflection curves (both the ascending and descending parts but also the maximum load capacity. The columns that can be analyzed include solid and hollow (rectangular, circular, oval, C-, T-, L-, or any arbitrary shape cross sections and columns made of circular and rectangular steel tubes filled with HSC. The fiber method is used to calculate the moment-curvature diagrams at different levels of the applied axial load (i.e., the M-P-φ curves, and the Gauss method of integration (for the sum of the contributions of the fibers parallel to the neutral axis is used to calculate the lateral rotations and deflections along the column span. Long-term effects, such as creep and shrinkage of the concrete, are also included. However, the effects of the shear deformations and torsion along the member are not included. The validity of the proposed method is presented in a companion paper and compared against the experimental results for over seventy column specimens reported in the technical literature by different researchers.

  4. Stress-strain relationship and XRD line broadening in [0001] textured hexagonal polycrystalline materials

    International Nuclear Information System (INIS)

    Stress analysis with X-ray diffraction (XRD) for hexagonal polycrystalline materials in the Laue classes 6/mmm and 6/m has been studied on the basis of the crystal symmetry of the constituent crystallites which was proposed by R. Yokoyama and J. Harada ['Re-evaluation of formulae for X-ray stress analysis in polycrystalline specimens with fibre texture', Journal of Applied Crystallography, Vol.42, pp.185-191 (2009)]. The relationship between the stress and strain observable by XRD in a hexagonal polycrystalline material with [0001] fibre texture was formulated in terms of the elastic compliance defined for its single crystal. As a result, it was shown that the average strains obtained in the crystallites for both symmetries of 6/mmm and 6/m are different from each other under the triaxial or biaxial stress field. Then, it turned out that the line width of XRD changes depending on the measurement direction. (author)

  5. Stress and structural damage sensing piezospectroscopic coatings validated with digital image correlation

    Directory of Open Access Journals (Sweden)

    Gregory Freihofer

    2015-03-01

    Full Text Available The piezospectroscopic effect, relating a material’s stress state and spectral signature, has recently demonstrated tailorable sensitivity when the photo-luminescent alpha alumina is distributed in nanoparticulate form within a matrix. Here, the stress-sensing behavior of an alumina-epoxy nanoparticle coating, applied to a composite substrate in an open hole tension configuration, is validated with the biaxial strain field concurrently determined through digital image correlation. The coating achieved early detection of composite failure initiation at 77% failure load, and subsequently tracked stress distribution in the immediate vicinity of the crack as it progressed, demonstrating non-invasive stress and damage detection with multi-scale spatial resolution.

  6. On the determination of Poisson's ratio of stressed monolayer and bilayer submicron thick films

    CERN Document Server

    Martins, P; Brida, S; Barbier, D

    2008-01-01

    In this paper, the bulge test is used to determine the mechanical properties of very thin dielectric membranes. Commonly, this experimental method permits to determine the residual stress (s0) and biaxial Young's modulus (E/(1-u)). Associating square and rectangular membranes with different length to width ratios, the Poisson's ratio (u) can also be determined. LPCVD Si3N4 monolayer and Si3N4/SiO2 bilayer membranes, with thicknesses down to 100 nm, have been characterized giving results in agreement with literature for Si3N4, E = 212 $\\pm$ 14 GPa, s0 = 420 $\\pm$ 8 and u = 0.29.

  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

    with a diameter of 5 mm is subsequently applied to the specimen and the released strains after drilling are measured using the Digital Image Correlation (DIC) technique. The material characterization of the utilized epoxy material is obtained from the experimental tests such as differential scanning calorimetry...... 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. Experimental evaluation of the pure configurational stress assumption in the flow dynamics of entangled polymer melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Bejenariu, Anca Gabriela; Hassager, Ole;

    2010-01-01

    A filament stretching rheometer was used for measuring the startup of uni-axial elongational flow followed by reversed bi-axial flow, both with a constant elongational strain rate. A narrow molecular mass distribution linear polyisoprene with a molecular weight of 483 kg/mole was subjected...... with the assumption of pure configurational stress was accurately able to predict the startup as well as the reversed flow behavior. This confirms that this commonly used theoretical picture for the flow of polymeric liquids is a correct physical principle to apply. c 2010 The Society of Rheology. [DOI: 10.1122/1.3496378]...

  9. Twist viscosities and flow alignment of biaxial nematic liquid crystal phases of a soft ellipsoid-string fluid studied by molecular dynamics simulation.

    Science.gov (United States)

    Sarman, Sten; Laaksonen, Aatto

    2012-09-14

    We have calculated the twist viscosity and the alignment angle between the director and the stream lines in shear flow of a liquid crystal model system, which forms biaxial nematic liquid crystals, as functions of the density, from the Green-Kubo relations by equilibrium molecular dynamics simulation and by a nonequilibrium molecular dynamics algorithm, where a torque conjugate to the director angular velocity is applied to rotate the director. The model system consists of a soft ellipsoid-string fluid where the ellipsoids interact according a repulsive version of the Gay-Berne potential. Four different length-to-width-to-breadth ratios have been studied. On compression, this system forms discotic or calamitic uniaxial nematic phases depending on the dimensions of the molecules, and on further compression a biaxial nematic phase is formed. In the uniaxial nematic phase there is one twist viscosity and one alignment angle. In the biaxial nematic phase there are three twist viscosities and three alignment angles corresponding to the rotation around the various directors and the different alignments of the directors relative to the stream lines, respectively. It is found that the smallest twist viscosity arises by rotation around the director formed by the long axes, the second smallest one arises by rotation around the director formed by the normals of the broadsides, and the largest one by rotation around the remaining director. The first twist viscosity is rather independent of the density whereas the last two ones increase strongly with density. One finds that there is one stable director alignment relative to the streamlines, namely where the director formed by the long axes is almost parallel to the stream lines and where the director formed by the normals of the broadsides is almost parallel to the shear plane. The relative magnitudes of the components of the twist viscosities span a fairly wide interval so this model should be useful for parameterisation

  10. Nuclear stress test

    Science.gov (United States)

    ... Persantine stress test; Thallium stress test; Stress test - nuclear; Adenosine stress test; Regadenoson stress test; CAD - nuclear stress; Coronary artery disease - nuclear stress; Angina - nuclear ...

  11. Voltage controlled biaxial strain in VO2 films grown on 0.72Pb(Mg1/3Nb2/3)-0.28PbTiO3 crystals and its effect on the transition temperature

    Science.gov (United States)

    Petraru, A.; Soni, R.; Kohlstedt, H.

    2014-09-01

    Vanadium oxide thin films (VO2) were deposited on 0.72Pb(Mg1/3Nb2/3)-0.28PbTiO3 (PMN-PT) crystalline substrates using pulsed laser deposition method. Due to their huge piezoelectric coefficients in the order of 2500 pm/V, the PMN-PT substrates are used to impose additional amount of biaxial strain to the VO2 films by applying an external bias to the substrates. The influence of the biaxial strain on the transition temperature and on the conductive properties of the VO2 films is investigated in this work. Thus, a change in the biaxial strain of -0.8 × 10-3 applied in the (110) plane of the rutile cell of the VO2 lowered the metal-to-insulator transition temperature by 1.35 °C.

  12. Fourier space method for calculating the propagation of laser radiation in biaxial crystals taking into account the angle between the eigenpolarisations

    International Nuclear Information System (INIS)

    We have proposed a technique for calculating the propagation of laser radiation in biaxial optical crystals in arbitrary directions. The technique is based on the use of the Fourier space method and takes into account both diffraction and angle beween the eigenpolarisations of the spatial spectrum components, phase shift differences for them with account for all orders of the spatial dispersion and also the features of the boundary conditions at the input and output facets. Using internal conical refraction as an example, we have compared the results of calculations with experimental data. (nonlinear optical phenomena)

  13. 1.9% bi-axial tensile strain in thick germanium suspended membranes fabricated in optical germanium-on-insulator substrates for laser applications

    Science.gov (United States)

    Gassenq, A.; Guilloy, K.; Osvaldo Dias, G.; Pauc, N.; Rouchon, D.; Hartmann, J.-M.; Widiez, J.; Tardif, S.; Rieutord, F.; Escalante, J.; Duchemin, I.; Niquet, Y.-M.; Geiger, R.; Zabel, T.; Sigg, H.; Faist, J.; Chelnokov, A.; Reboud, V.; Calvo, V.

    2015-11-01

    High tensile strains in Ge are currently studied for the development of integrated laser sources on Si. In this work, we developed specific Germanium-On-Insulator 200 mm wafer to improve tolerance to high strains induced via shaping of the Ge layers into micro-bridges. Building on the high crystalline quality, we demonstrate bi-axial tensile strain of 1.9%, which is currently the highest reported value measured in thick (350 nm) Ge layer. Since this strain is generally considered as the onset of the direct bandgap in Ge, our realization paves the way towards mid-infrared lasers fully compatible with CMOS fab technology.

  14. Edge wrinkling in elastically supported pre-stressed incompressible isotropic plates

    Science.gov (United States)

    Destrade, Michel; Fu, Yibin; Nobili, Andrea

    2016-09-01

    The equations governing the appearance of flexural static perturbations at the edge of a semi-infinite thin elastic isotropic plate, subjected to a state of homogeneous bi-axial pre-stress, are derived and solved. The plate is incompressible and supported by a Winkler elastic foundation with, possibly, wavenumber dependence. Small perturbations superposed onto the homogeneous state of pre-stress, within the three-dimensional elasticity theory, are considered. A series expansion of the plate kinematics in the plate thickness provides a consistent expression for the second variation of the potential energy, whose minimization gives the plate governing equations. Consistency considerations supplement a constraint on the scaling of the pre-stress so that the classical Kirchhoff-Love linear theory of pre-stretched elastic plates is retrieved. Moreover, a scaling constraint for the foundation stiffness is also introduced. Edge wrinkling is investigated and compared with body wrinkling. We find that the former always precedes the latter in a state of uni-axial pre-stretch, regardless of the foundation stiffness. By contrast, a general bi-axial pre-stretch state may favour body wrinkling for moderate foundation stiffness. Wavenumber dependence significantly alters the predicted behaviour. The results may be especially relevant to modelling soft biological materials, such as skin or tissues, or stretchable organic thin-films, embedded in a compliant elastic matrix.

  15. Film stresses and electrode buckling in organic solar cells

    KAUST Repository

    Brand, Vitali

    2012-08-01

    We investigate the film stresses that develop in the polymer films and metal electrodes of poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) bulk heterojunction (BHJ) organic solar cells. A compressive biaxial stress of ∼-36 MPa was measured in PEDOT:PSS while a tensile stress of ∼6 MPa was measured in the BHJ layer. We then analyze the effect of electrode deposition rate on the film stresses in the Al electrode. Compressive stresses of ∼-100 to -145 MPa in the Al electrode lead to a buckling instability resulting in undulating electrode surface topography. The BHJ layer was found to have the lowest cohesion (∼1.5-1.8 J/m 2) among the layers of the solar cell and dependent on the Al electrode deposition rate. The cohesive failure path in the BHJ layer exhibited the same periodicity and orientation of the Al electrode buckling topography. We discuss the implications of the film stresses on damage processes during device fabrication and operation. © 2012 Elsevier B.V. All rights reserved.

  16. Macroscopic biaxiality and electric-field-induced rotation of the minor director in the nematic phase of a bent-core liquid crystal

    Science.gov (United States)

    Nagaraj, Mamatha; Merkel, K.; Vij, J. K.; Kocot, A.

    2010-09-01

    Biaxiality in the nematic phase has been investigated for the bent-core liquid-crystal para-heptylbenzoate diester, using polarised IR spectroscopy. Anisotropic fluctuations of the nematic director are discussed in terms of the self-assembly of the chiral conformers. The ordering of the minor director for the homeotropicaly aligned sample is found to depend on the rubbing of the substrates of the cell and the amplitude of in-plane electric field. On increasing the in-plane electric field, the rotation of the minor director in the plane of the substrate is observed with an angle of approximately 45°, where initially the minor director is shown to lie along the rubbing direction. It is also shown that on the average the long axis of the molecules is normal to the substrate with surface treatment, with and without rubbing. The electric in-plane field combined with rubbing is shown to induce biaxial order in the nematic phase of a material with negative dielectic anisotropy for the first time.

  17. Multi-mode technique for the determination of the biaxial Y{sub 2}SiO{sub 5} permittivity tensor from 300 to 6 K

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, N. C., E-mail: natalia.docarmocarvalho@research.uwa.edu.au; Le Floch, J-M.; Tobar, M. E. [School of Physics, The University of Western Australia, Crawley 6009 (Australia); ARC Centre of Excellence for Engineered Quantum Systems (EQuS), 35 Stirling Hwy, Crawley 6009 (Australia); Krupka, J. [Instytut Mikroelektroniki i Optoelektroniki PW, Koszykowa 75, 00-662 Warsaw (Poland)

    2015-05-11

    The Y{sub 2}SiO{sub 5} (YSO) crystal is a dielectric material with biaxial anisotropy with known values of refractive index at optical frequencies. It is a well-known rare-earth (RE) host material for optical research and more recently has shown promising performance for quantum-engineered devices. In this paper, we report the first microwave characterization of the real permittivity tensor of a bulk YSO sample, as well as an investigation of the temperature dependence of the tensor components from 296 K down to 6 K. Estimated uncertainties were below 0.26%, limited by the precision of machining the cylindrical dielectric. Also, the electrical Q-factors of a few electromagnetic modes were recorded as a way to provide some information about the crystal losses over the temperature range. To solve the tensor components necessary for a biaxial crystal, we developed the multi-mode technique, which uses simultaneous measurement of low order whispering gallery modes. Knowledge of the permittivity tensor offers important data, essential for the design of technologies involving YSO, such as microwave coupling to electron and hyperfine transitions in RE doped samples at low temperatures.

  18. Distribution and viability of fetal and adult human bone marrow stromal cells in a biaxial rotating vessel bioreactor after seeding on polymeric 3D additive manufactured scaffolds

    Directory of Open Access Journals (Sweden)

    Anne eLeferink

    2015-10-01

    Full Text Available One of the conventional approaches in tissue engineering is the use of scaffolds in combination with cells to obtain mechanically stable tissue constructs in vitro prior to implantation. Additive manufacturing by fused deposition modeling is a widely used technique to produce porous scaffolds with defined pore network, geometry, and therewith defined mechanical properties. Bone marrow derived mesenchymal stromal cells (MSCs are promising candidates for tissue engineering based cell therapies due to their multipotent character. One of the hurdles to overcome when combining additive manufactured scaffolds with MSCs is the resulting heterogeneous cell distribution and limited cell proliferation capacity. In this study, we show that the use of a biaxial rotating bioreactor, after static culture of human fetal MSCs (hfMSCs seeded on synthetic polymeric scaffolds, improved the homogeneity of cell and extracellular matrix (ECM distribution and increased the total cell number. Furthermore, we show that the relative mRNA expression levels of indicators for stemness and differentiation are not significantly changed upon this bioreactor culture, whereas static culture shows variations of several indicators for stemness and differentiation. The biaxial rotating bioreactor presented here offers a homogeneous distribution of hfMSCs, enabling studies on MSCs fate in additive manufactured scaffolds without inducing undesired differentiation.

  19. Semicrystalline Structure-Dielectric Property Relationship and Electrical Conduction in a Biaxially Oriented Poly(vinylidene fluoride) Film under High Electric Fields and High Temperatures.

    Science.gov (United States)

    Yang, Lianyun; Ho, Janet; Allahyarov, Elshad; Mu, Richard; Zhu, Lei

    2015-09-16

    Poly(vinylidene fluoride) (PVDF)-based homopolymers and copolymers are attractive for a broad range of electroactive applications because of their high dielectric constants. Especially, biaxially oriented PVDF (BOPVDF) films exhibit a DC breakdown strength as high as that for biaxially oriented polypropylene films. In this work, we revealed the molecular origin of the high dielectric constant via study of a commercial BOPVDF film. By determination of the dielectric constant for the amorphous phase in BOPVDF, a high value of ca. 21-22 at 25 °C was obtained, and a three-phase (i.e., lamellar crystal/oriented interphase/amorphous region) semicrystalline model was proposed to explain this result. Meanwhile, electronic conduction mechanisms in BOPVDF under high electric fields and elevated temperatures were investigated by thermally stimulated depolarization current (TSDC) spectroscopy and leakage current studies. Space charge injection from metal electrodes was identified as a major factor for electronic conduction when BOPVDF was poled above 75 °C and 20 MV/m. In addition, when silver or aluminum were used as electrodes, new ions were generated from electrochemical reactions under high fields. Due to the electrochemical reactions between PVDF and the metal electrode, a question is raised for practical electrical applications using PVDF and its copolymers under high-field and high-temperature conditions. A potential method to prevent electrochemical degradation of PVDF is proposed in this study.

  20. On the Novel Biaxial Strain Relaxation Mechanism in Epitaxial Composition Graded La1−xSrxMnO3 Thin Film Synthesized by RF Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Yishu Wang

    2015-11-01

    Full Text Available We report on a novel method to fabricate composition gradient, epitaxial La1−xSrxMnO3 thin films with the objective to alleviate biaxial film strain. In this work, epitaxial, composition gradient La1−xSrxMnO3, and pure LaMnO3 and La0.67Sr0.33MnO3 thin films were deposited by radio frequency (RF magnetron sputtering. The crystalline and epitaxy of all films were first studied by symmetric θ–2θ X-ray diffraction (XRD and low angle XRD experiments. Detailed microstructural characterization across the film thickness was conducted by high-resolution transmission electron microscopy and electron diffraction. Four compositional gradient domains were observed in the La1−xSrxMnO3 film ranging from LaMnO3 rich to La0.67Sr0.33MnO3 at the surface. A continuous reduction in the lattice parameter was observed accompanied by a significant reduction in the out-of-plane strain in the film. Fabrication of the composition gradient La1−xSrxMnO3 thin film was found to be a powerful method to relieve biaxial strain under critical thickness. Besides, the coexistence of domains with a composition variance is opening up various new possibilities of designing new nanoscale structures with unusual cross coupled properties.

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

    International Nuclear Information System (INIS)

    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)

  2. Biaxially textured composite substrates

    Energy Technology Data Exchange (ETDEWEB)

    Groves, James R.; Foltyn, Stephen R.; Arendt, Paul N.

    2005-04-26

    An article including a substrate, a layer of a metal phosphate material such as an aluminum phosphate material upon the surface of the substrate, and a layer of an oriented cubic oxide material having a rock-salt-like structure upon the metal phosphate material layer is provided together with additional layers such as a HTS top-layer of YBCO directly upon a layer of a buffer material such as a SrTi.sub.x Ru.sub.1-x O.sub.3 layer.

  3. Contraction stress, elastic modulus, and degree of conversion of three flowable composites.

    Science.gov (United States)

    Cadenaro, Milena; Codan, Barbara; Navarra, Chiara O; Marchesi, Giulio; Turco, Gianluca; Di Lenarda, Roberto; Breschi, Lorenzo

    2011-06-01

    The aim of this study was to measure the contraction stress of three flowable resin composites and to correlate the stress with the elastic modulus and the degree of conversion. One low-shrinkage (Venus Diamond Flow) and two conventional (Tetric EvoFlow and X-Flow) flowable composites were polymerized for 40s with a light-emitting diode (LED) curing unit. Contraction force was continuously recorded for 300s using a stress-analyser, and stress values were calculated at 40s and at 300s. The maximum stress rate was also calculated for each specimen. The elastic modulus of each composite was assayed using a biaxial flexural test, and degree of conversion was analysed with Raman spectroscopy. X-Flow exhibited higher stress values than the other tested materials. Venus Diamond Flow showed the lowest stress values at 40s and at 300s, and the lowest maximum stress rate. Stress values were correlated with elastic modulus but not with degree of conversion, which was comparable among all tested materials.

  4. Heat Stress

    Science.gov (United States)

    ... Publications and Products Programs Contact NIOSH NIOSH HEAT STRESS Recommend on Facebook Tweet Share Compartir NEW Criteria ... hot environments may be at risk of heat stress. Exposure to extreme heat can result in occupational ...

  5. Cold Stress

    Science.gov (United States)

    ... Publications and Products Programs Contact NIOSH NIOSH COLD STRESS Recommend on Facebook Tweet Share Compartir Workers who ... cold environments may be at risk of cold stress. Extreme cold weather is a dangerous situation that ...

  6. Caregiver Stress

    Science.gov (United States)

    ... current/fahc.html/ Search Share Embed Caregiver stress Caregivers care for someone with an illness, injury, ... be rewarding, but it can also be challenging. Stress from caregiving is common. Women especially are at ...

  7. Application of a linear elastic - brittle interface model to the crack initiation and propagation at fibre-matrix interface under biaxial transverse loads

    CERN Document Server

    Mantič, V; Blázquez, A; Graciani, E; París, F

    2013-01-01

    The crack onset and propagation at the fibre-matrix interface in a composite under tensile/compressive remote biaxial transverse loads is studied by a new linear elastic - (perfectly) brittle interface model. In this model the interface is represented by a continuous distribution of springs which simulates the presence of a thin elastic layer. The constitutive law for the continuous distribution of normal and tangential of initially linear elastic springs takes into account possible frictionless elastic contact between fibre and matrix once a portion of the interface is broken. A brittle failure criterion is employed for the distribution of springs, which enables the study of crack onset and propagation. This interface failure criterion takes into account the variation of the interface fracture toughness with the fracture mode mixity. The main advantages of the present interface model are its simplicity, robustness and its computational efficiency when the so-called sequentially linear analysis is applied. Mo...

  8. The biaxial nonlinear crystal BiB3O6 as a polarization entangled photon source using non-collinear type-II parametric down-conversion

    CERN Document Server

    Halevy, A; Dovrat, L; Eisenberg, H S; Becker, P; Bohatý, L

    2011-01-01

    We describe the full characterization of the biaxial nonlinear crystal BiB3O6 (BiBO) as a polarization entangled photon source using non-collinear type-II parametric down-conversion. We consider the relevant parameters for crystal design, such as cutting angles, polarization of the photons, effective nonlinearity, spatial and temporal walk-offs, crystal thickness and the effect of the pump laser bandwidth. Experimental results showing entanglement generation with high rates and a comparison to the well investigated beta-BaB2O4 (BBO) crystal are presented as well. Changing the down-conversion crystal of a polarization entangled photon source from BBO to BiBO enhances the generation rate as if the pump power was increased by more than three times. Such an improvement is currently required for the generation of multiphoton entangled states.

  9. The biaxial nonlinear crystal BiB₃O₆ as a polarization entangled photon source using non-collinear type-II parametric down-conversion.

    Science.gov (United States)

    Halevy, A; Megidish, E; Dovrat, L; Eisenberg, H S; Becker, P; Bohatý, L

    2011-10-10

    We describe the full characterization of the biaxial nonlinear crystal BiB₃O₆ (BiBO) as a polarization entangled photon source using non-collinear type-II parametric down-conversion. We consider the relevant parameters for crystal design, such as cutting angles, polarization of the photons, effective nonlinearity, spatial and temporal walk-offs, crystal thickness and the effect of the pump laser bandwidth. Experimental results showing entanglement generation with high rates and a comparison to the well investigated β-BaB₂O₄ (BBO) crystal are presented as well. Changing the down-conversion crystal of a polarization entangled photon source from BBO to BiBO enhances the generation rate as if the pump power was increased by 2.5 times. Such an improvement is currently required for the generation of multiphoton entangled states.

  10. Effect of biaxial strain induced by piezoelectric PMN-PT on the upconversion photoluminescence of BaTiO₃:Yb/Er thin films.

    Science.gov (United States)

    Wu, Zhenping; Zhang, Yang; Bai, Gongxun; Tang, Weihua; Gao, Ju; Hao, Jianhua

    2014-11-17

    Thin films of Yb3+/Er3+ co-doped BaTiO3 (BTO:Yb/Er) have been epitaxially grown on piezoelectric Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) substrates. Biaxial strain can be effectively controlled by applying electric field on PMN-PT substrate. A reversible, in situ and dynamic modification of upconversion photoluminescence in BTO:Yb/Er film was observed via converse piezoelectric effect. Detailed analysis and in situ X-ray diffraction indicate that such modulations are possibly due to the change in the lattice deformation of the thin films. This result suggests an alternative method to rationally tune the upconversion emissions via strain engineering. PMID:25402140

  11. The biaxial nonlinear crystal BiB₃O₆ as a polarization entangled photon source using non-collinear type-II parametric down-conversion.

    Science.gov (United States)

    Halevy, A; Megidish, E; Dovrat, L; Eisenberg, H S; Becker, P; Bohatý, L

    2011-10-10

    We describe the full characterization of the biaxial nonlinear crystal BiB₃O₆ (BiBO) as a polarization entangled photon source using non-collinear type-II parametric down-conversion. We consider the relevant parameters for crystal design, such as cutting angles, polarization of the photons, effective nonlinearity, spatial and temporal walk-offs, crystal thickness and the effect of the pump laser bandwidth. Experimental results showing entanglement generation with high rates and a comparison to the well investigated β-BaB₂O₄ (BBO) crystal are presented as well. Changing the down-conversion crystal of a polarization entangled photon source from BBO to BiBO enhances the generation rate as if the pump power was increased by 2.5 times. Such an improvement is currently required for the generation of multiphoton entangled states. PMID:21997051

  12. Comparison of Some Mechanical and Physical Methods for Measurement of Residual Stresses in Brush-Plated Nickel Hardened Gold and Silver Coatings

    Directory of Open Access Journals (Sweden)

    Harri LILLE

    2016-05-01

    Full Text Available Hard gold and silver are applied in coating owing to their high hardness, good wear and corrosion resistance for engineering application (e.g. on generators slip rings, sliding contacts and small machine parts and are typically plated on copper (mostly, brass and bronze. The studied nickel-hardened gold and silver coatings were brush plated on open thin-walled copper ring substrates. Residual stresses in the coatings were calculated from the curvature changes of the substrates. Biaxial intrinsic residual stresses were also determined by nanoindentation testing and by the X-ray technique. The values of the residual stresses represented tensile stresses and when determined by the techniques used they were comparable within a maximum limit of measurement uncertainty. These stresses relax; the dependence of relaxation time was approximated by a linear-fractional function.DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7439

  13. Feeling Stressed

    Science.gov (United States)

    ... of depression, which needs treatment. Learn more about depression and how to get help. How does my body act when stressed? top Your body has a ... stress doesn't feel very good. When your body is hit by stress, try to calm it down. Taking some deep ... anxiety disorders , alcohol and drug abuse , smoking , and ...

  14. Development of Biaxially Textured YBa{sub 2}Cu{sub 3}O{sub 7} Coated Conductors in the U.S.

    Energy Technology Data Exchange (ETDEWEB)

    Christen, D.K.; Hawsey, R.A.; Kroeger, D.M.

    1999-11-13

    Two new processes have been under development since 1991 that promise a new, cost-effective way to manufacture flexible, high current density wires made from YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO). The key is to prepare a textured substrate, or ''template,'' on which the YBCO may be deposited as a biaxially aligned thick film. Ion beam assisted deposition (IBAD) of yttria stabilized zirconia or magnesium oxide on alloy tapes enables a final superconducting layer with grain-to-grain, in-plane alignment to within 3-5 degrees. Similar results are achieved on rolling-assisted, biaxially textured substrates (RABiTS) using a variety of oxide layers on textured nickel tapes. The performance of research lengths of prototype wires in strong magnetic fields at 65 K already exceeds that of NbTi and Nb{sub 3}Sn in liquid helium. A scalable, ex-situ process for the YBCO coating has been demonstrated on both types of substrates. Consistent values of critical current density (J{sub c }) greater than 1 x 10{sup 6} A/cm{sup 2} are now obtained on RABiTS, and J{sub c}'s in excess of 2 x 10{sup 6} A/cm{sup 2} have been obtained on both substrates. A nonmagnetic variation of RABiTS (Ni-13% Cr) has also been shown to yield Jc greater than 1.5 x 10{sup 6} A/cm{sup 2} . Six private companies in the U.S. are scaling up YBCO coated conductors for power and physics applications.

  15. 双轴压缩条件下碎石集料静力剪切特性研究%Static Shear Behavior of Crushed Rock Aggregate Subjected to Biaxial Compression

    Institute of Scientific and Technical Information of China (English)

    王鹏程; 刘建坤; 李旭; 房建宏

    2014-01-01

    基于离散单元法,利用PFC2D内置Fish语言编制碎石集料双轴实验条件,结合计算机语言与PFC2D中Clump命令编制将球形单元转化为随机多边形块体单元的程序。通过对比室内大型三轴试验对数值模型进行参数标定与验证,在此基础上分析3种典型粒径碎石集料的应力-应变特性以及抗剪强度特性。结果表明,围压对集料的应力-应变特性影响明显。对于不同粒径的碎石集料而言,随着围压的增加,偏应力峰值增加而应力比减小;在本文选定的围压范围内碎石集料均呈现出先压缩最终剪胀的特性,围压越大,压缩量大,最终的剪胀越不明显;碎石集料的强度包络线为非线性,相同围压条件下的抗剪强度随着粒径的增大而增加;表征摩擦角随围压的增加而减小,相同围压下,粒径越大,表征摩擦角也越大。%With the discrete element method(DEM ) ,biaxial compressions test conditions for crushed rock aggre-gate were established in the Fish language and the Clump logic commands in PFC 2D were incorporated into the computer language to simulate the crushed rock aggregate of irregular shapes .Compared with large-scale labo-ratory triaxial tests ,the parameters of the numerical model were calibrated and validated .The stress-deforma-tion and shearing strength of the crushed stone aggregate of three typical particle sizes were analyzed .The re-search results demonstrate as follws :The confining pressure influences the stress-strain characteristics of aggre-gate significantly ;for aggregate of different particle sizes ,along with adding of the confining pressure ,the peak deviatoric stress increases while the stress ratio decreases ;within the specified range of confining pressure initial compression and subsequent dilation are observed with the aggregate ,the higher the confining pressure ,the lar-ger the compression and the smaller the dilation ;the shear strength

  16. Cyclic uniaxial and biaxial hardening of type 304 stainless steel modeled by the viscoplasticity theory based on overstress

    Science.gov (United States)

    Yao, David; Krempl, Erhard

    1988-01-01

    The isotropic theory of viscoplasticity based on overstress does not use a yield surface or a loading and unloading criterion. The inelastic strain rate depends on overstress, the difference between the stress and the equilibrium stress, and is assumed to be rate dependent. Special attention is paid to the modeling of elastic regions. For the modeling of cyclic hardening, such as observed in annealed Type 304 stainless steel, and additional growth law for a scalar quantity which represents the rate independent asymptotic value of the equilibrium stress is added. It is made to increase with inelastic deformation using a new scalar measure which differentiates between nonproportional and proportional loading. The theory is applied to correlate uniaxial data under two step amplitude loading including the effect of further hardening at the high amplitude and proportional and nonproportional cyclic loadings. Results are compared with corresponding experiments.

  17. Modeling of delayed strains of concrete under biaxial loadings. Application to the reactor containment of nuclear power plants; Modelisation des deformations differees du beton sous sollicitations biaxiales. application aux enceintes de confinement de batiments reacteurs des centrales nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Benboudjema, F

    2002-12-15

    The prediction of delayed strains is of crucial importance for durability and long-term serviceability of concrete structures (bridges, containment vessels of nuclear power plants, etc.). Indeed, creep and shrinkage cause cracking, losses of pre-stress and redistribution of stresses, and also, rarely, the ruin of the structure. The objective of this work is to develop numerical tools, able to predict the long-term behavior of concrete structures. Thus, a new hydro mechanical model is developed, including the description of drying, shrinkage, creep and cracking phenomena for concrete as a non-saturated porous medium. The modeling of drying shrinkage is based on an unified approach of creep and shrinkage. Basic and drying creep models are based on relevant chemo-physical mechanisms, which occur at different scales of the cement paste. The basic creep is explicitly related to the micro-diffusion of the adsorbed water between inter-hydrates and intra-hydrates and the capillary pores, and the sliding of the C-S-H gel at the nano-porosity level. The drying creep is induced by the micro-diffusion of the adsorbed water at different scales of the porosity, under the simultaneous effects of drying and mechanical loadings. Drying shrinkage is, therefore, assumed to result from the elastic and delayed response of the solid skeleton, submitted to both capillary and disjoining pressures. Furthermore, the cracking behavior of concrete is described by an orthotropic elastoplastic damage model. The coupling between all these phenomena is performed by using effective stresses which account for both external applied stresses and pore pressures. This model has been incorporated into a finite element code. The analysis of the long-term behavior is also performed on concrete specimens and prestressed concrete structures submitted to simultaneous drying and mechanical loadings. (author)

  18. Effects of Stress and Void-Void Interactions on Current-Driven Void Surface Evolution in Metallic Thin Films

    Science.gov (United States)

    Cho, Jaeseol; Gungor, M. Rauf; Maroudas, Dimitrios

    2006-03-01

    We report results of electromigration- and stress-induced migration and morphological evolution of voids in metallic thin films based on self-consistent numerical simulations. The analysis reveals the complex nature of void-void interactions and their implications for the evolution of metallic thin-film electrical resistance, providing interpretation for experimental measurements in interconnect lines. Interestingly, for two voids migrating in the same direction under certain conditions, we find that a smaller void does not always approach and coalesce with a larger one, while a larger void may approach and coalesce with a smaller one. In addition, we find that under certain electromechanical conditions, biaxially applied mechanical stress can cause substantial retardation of void motion, as measured by the constant speed of electromigration-induced translation of morphologically stable voids. This effect suggests the possibility for complete inhibition of current-driven void motion under stress.

  19. Intrinsic stress in ZrN thin films: Evaluation of grain boundary contribution from in situ wafer curvature and ex situ x-ray diffraction techniques

    Energy Technology Data Exchange (ETDEWEB)

    Koutsokeras, L. E. [Departement Physique et Mecanique des Materiaux, Institut Pprime, CNRS-Universite de Poitiers-ENSMA, UPR 3346, SP2MI, Teleport 2, Bd M et P Curie, F 86962 Chasseneuil-Futuroscope (France); Department of Materials Science and Engineering, University of Ioannina, Ioannina 45110 (Greece); Abadias, G. [Departement Physique et Mecanique des Materiaux, Institut Pprime, CNRS-Universite de Poitiers-ENSMA, UPR 3346, SP2MI, Teleport 2, Bd M et P Curie, F 86962 Chasseneuil-Futuroscope (France)

    2012-05-01

    Low-mobility materials, like transition metal nitrides, usually undergo large residual stress when sputter-deposited as thin films. While the origin of stress development has been an active area of research for high-mobility materials, atomistic processes are less understood for low-mobility systems. In the present work, the contribution of grain boundary to intrinsic stress in reactively magnetron-sputtered ZrN films is evaluated by combining in situ wafer curvature measurements, providing information on the overall biaxial stress, and ex situ x-ray diffraction, giving information on elastic strain (and related stress) inside crystallites. The thermal stress contribution was also determined from the in situ stress evolution during cooling down, after deposition was stopped. The stress data are correlated with variations in film microstructure and growth energetics, in the 0.13-0.42 Pa working pressure range investigated, and discussed based on existing stress models. At low pressure (high energetic bombardment conditions), a large compressive stress is observed due to atomic peening, which induces defects inside crystallites but also promotes incorporation of excess atoms in the grain boundary. Above 0.3-0.4 Pa, the adatom surface mobility is reduced, leading to the build-up of tensile stress resulting from attractive forces between under-dense neighbouring column boundary and possible void formation, while crystallites can still remain under compressive stress.

  20. Application of heart coronary vascular biaxial rotation technique%心脏冠脉双轴旋转血管造影技术应用

    Institute of Scientific and Technical Information of China (English)

    崔永强

    2015-01-01

    目的:了解心脏冠脉双轴旋转血管造影技术的临床应用效果。方法对驻马店市中心医院2012年3月至2014年3月收治的接受冠脉造影检查的患者进行抽样,选取60例患者随机分成两组,对照组予以常规冠状动脉造影术,实验组行双轴旋转冠脉造影术,观察两组检查透视时间、心脏平均吸收剂量、图像质量评分及对比剂用量变化差异。结果实验组心脏平均吸收剂量为(30.38±13.38) D/mGy,明显低于对照组的(32.28±15.01)D/mGy,对比剂用量为(29.68±0.08)V/ml,显著低于对照组的(41.08±7.73)V/ml,差异有统计学意义(P<0.05);两组透视时间、图像质量评分比较差异均未见统计学意义(P>0.05)。结论冠脉双轴旋转血管造影技术与冠脉造影图像质量要求吻合,可有效减少冠脉造影的辐射剂量及对比剂用量,临床上应引起足够重视。%Objective To investigate the clinical application effect of coronary heart biaxial rotation angiography technique.Methods Sixty patients in Central Hospital of Zhumadian from March 2012 to March 2014 accepted coronary angiography for sampling.They were randomly divided into two groups, and the control group was given routine coronary angiography, the experiment group were given biaxial rotation coronary angiography, The cardiac fluoroscopy time, average absorbed dose, image quality scores and comparison dosage change of two groups were observed.Results In experiment group, the average absorbed dose to the heart ( 30.38 ±13.38 ) D/mGy was significantly lower than that of the control group (32.28 ±15.01) D/mGy, and dosage of contrast medium (29.68 ±0.08) V/ml was significantly lower than that of the control group (41.08 ±7.73) V/ml, the differences were significant (P0.05).Conclusions Coronary biaxial rotation angiography tech-nique meet coronary angiography image quality requirement, it can effectively reduce the

  1. Debriefing Stress.

    Science.gov (United States)

    Hill, Jonnie L.; Lance, Cynthia G.

    2002-01-01

    Discussion pf the stress associated with the educational use of games and simulations focuses on a study of graduate students that used the Myers-Briggs Type Indicator to determine that people with certain personality types experience stress at different intensities. Also found that all participants, regardless of personality type, needed…

  2. Geopotential Stress

    DEFF Research Database (Denmark)

    Schiffer, Christian; Nielsen, S.B.

    Density heterogeneity in the Earth’s lithosphere causes lateral pressure variations. Horizontal gradients of the vertically integrated lithostatic pressure, the Geopotential Energy (GPE), are a source of stresses (Geopotential Stress) that contribute to the Earth’s Stress Field. In theory the GPE...... is linearly related to the lithospheric part of the Geoid. The Geopotential Stress can be calculated if either the density structure and as a consequence the GPE or the lithospheric contribution to the Geoid is known. The lithospheric Geoid is usually obtained by short pass filtering of satellite Geoid...... are not entirely suitable for the stress calculations but can be compiled and adjusted. We present an approach in which a global lithospheric density model based on CRUST2.0 is obtained by simultaneously fitting topography and surface heat flow in the presence of isostatic compensation and long-wavelength lateral...

  3. Annealing induced coherent evolutions of biaxial strain and antiferromagnetic-insulator phase in La0.625Ca0.375MnO3 films

    Science.gov (United States)

    Han, Yunxin; Wu, Wenbin; Jiang, Guoshun; Zhu, Changfei

    2012-09-01

    La0.625Ca0.375MnO3 (LCMO) films with thicknesses between 7 and 54 nm were epitaxially grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) [LSAT (001)] substrates by using pulsed laser deposition. For this epitaxial system, antiferromagnetic-insulator (AFI) state can be controlled by changing the film thickness and annealing time with various epitaxial strain states, although this phenomenon is absent in the relatively thick films or bulk samples. The consistency between magnetization and resistivity data suggests all these interesting transport behaviors are attributed to the fluctuation of AFI volume fractions and their instability. Especially, there are huge low-field magnetoresistance over -54% (32 nm) at 0.1 T and enhanced magnetoresistance over a broad temperature range. Based on these above results, annealing induced coherent evolutions of biaxial strain and AFI phase in LCMO epitaxial films is a consequence of the strain-driven orbital ordered state, and this may make an approach for a possible application of strongly correlated electron devices.

  4. Analysis and optimization of oxide buffer layers related to YBCO films deposited by CSD and MOCVD on biaxially textured NiW substrates

    International Nuclear Information System (INIS)

    The studies based on epitaxial buffer layers of CeO2 and Yttria-stabilised ZrO2 (YSZ) having been deposited on biaxially textured nickel substrates using thermal reactive evaporation and rf sputtering in continuous deposition processes in reel-to-reel systems. Starting from the well known architecture of CeO2/YSZ/CeO2 the thickness of the different buffer layers was varied. Misorientation, porosity and roughness was analyzed and optimized for YBCO deposition by MOCVD und CSD. The grain morphology and the behavior of the grain boundary networks in YBCO coated conductors have been shown to depend on both the YBCO deposition method and the buffers layer. The possibility of using only one and two buffers layer and conductive layers of perovskite type was studied. X-ray-diffraction, SEM and TEM have been used to investigate the microstructure of both the buffer layers and the YBCO films. Optimal growth conditions of YBCO for the different buffer layers have been determined. YBCO films were deposited by CSD, MOCVD and for comparison by high pressure dc sputtering, resulting on CeO2/YSZ/CeO2 buffered substrates Jc values higher than 2 MA/cm2. The resulting superconducting properties were measured by inductive characterization and by Hall probe measurements of the magnetic field due to induced magnetization currents. (orig.)

  5. Three-Dimensional Packing Structure and Electronic Properties of Biaxially Oriented Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2- b ]thiophene) Films

    KAUST Repository

    Cho, Eunkyung

    2012-04-11

    We use a systematic approach that combines experimental X-ray diffraction (XRD) and computational modeling based on molecular mechanics and two-dimensional XRD simulations to develop a detailed model of the molecular-scale packing structure of poly(2,5-bis (3-tetradecylthiophene-2-yl) thieno[3,2-b]thiophene) (PBTTT-C 14) films. Both uniaxially and biaxially aligned films are used in this comparison and lead to an improved understanding of the molecular-scale orientation and crystal structure. We then examine how individual polymer components (i.e., conjugated backbone and alkyl side chains) contribute to the complete diffraction pattern, and how modest changes to a particular component orientation (e.g., backbone or side-chain tilt) influence the diffraction pattern. The effects on the polymer crystal structure of varying the alkyl side-chain length from C 12 to C 14 and C 16 are also studied. The accurate determination of the three-dimensional polymer structure allows us to examine the PBTTT electronic band structure and intermolecular electronic couplings (transfer integrals) as a function of alkyl side-chain length. This combination of theoretical and experimental techniques proves to be an important tool to help establish the relationship between the structural and electronic properties of polymer thin films. © 2012 American Chemical Society.

  6. Comparative Study on Tribological Behavior of Biaxial Glass Fiber/Al2O3/SiC Epoxy Journal Bearing Under Various Test Conditions

    Directory of Open Access Journals (Sweden)

    T. Narendiranath Babu

    2014-08-01

    Full Text Available Composite journal bearings are becoming more popular now a day because they eliminate the possibility of seizure failure to the bearings. The major drawback of the gun metal bearings is the seizure failure. To overcome this problem, the composite journal bearings are widely used by the industries. In this study, the fiber reinforced plastic composed of glass fiber with epoxy resin composite /Al2O3/SiC journal bearing having the composition of 10-20% are tested under various operating conditions and the results are compared with gun metal journal bearing. This study focuses on the dimensional stability, temperature, friction, surface roughness and surface topography behavior of biaxial glass fiber epoxy composite with and without lubrication at different speeds and loads. It has been observed that the friction and temperature increases with increase in load but it’s very less when compared to gun metal bearing. It is found that there is loss in weight due to increase in temperature and friction but the loss in weight is very less which is approximately 1 g. In the earlier research, most of the bearings are tested under very low speed with more catastrophic failure due to various loading conditions. Therefore in this study the composite journal bearing is tested from low speed to high speed with different loading conditions and their effects has been studied. This composite journal will save the significant cost to the industries by reducing the coefficient of friction, temperature, lubrication etc.

  7. Use of biaxially oriented polypropylene film for evaluating and cleaning contaminated atomic force microscopy probe tips: An application to blind tip reconstruction

    Science.gov (United States)

    Nie, H.-Y.; Walzak, M. J.; McIntyre, N. S.

    2002-11-01

    An atomic force microscopy (AFM) image of a surface is basically a convolution of the probe tip geometry and the surface features; it is important to know this tip effect to ensure that an image truly reflects the surface features. We have found that a biaxially oriented polypropylene (BOPP) film is suitable for checking tip performance and for cleaning contaminated tips, thus making it possible to collect images of the same area of a BOPP film surface before and after the tip was cleaned. Therefore, the difference between the two different images is solely due to the contamination of the tip. We took advantage of our ability to collect AFM images of the same area using the same tip, in one instance, contaminated and, in the other, after being cleaned. First we used blind reconstruction on the image collected using the contaminated tip. Blind tip reconstruction allows one to extract the geometry of the tip from a given image. Once we had estimated the geometry of the contaminated tip, we used it to simulate the tip effect using the image collected using the cleaned tip. By comparing the simulation result with the image collected using the contaminated tip we showed that the blind reconstruction routine works well. Prior to this, there was no de facto method for testing blind reconstruction algorithms.

  8. Effect of Low-Pressure Nitrogen DC Plasma Treatment on the Surface Properties of Biaxially Oriented Polypropylene, Poly (Methyl Methacrylate) and Polyvinyl Chloride Films

    Science.gov (United States)

    S. Hamideh, Mortazavi; Mahmood, Ghoranneviss; Soheil, Pilehvar; Sina, Esmaeili; Shamim, Zargham; S. Ebrahim, Hashemi; Hamzeh, Jodat

    2013-04-01

    In this study, commercial biaxially oriented polypropylene (BOPP), polyvinyl chloride (PVC) and poly (methyl methacrylate) (PMMA) films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemical changes that appeared on the surface of the samples were investigated using Fourier transform infrared (FT-IR) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy after treatment for 2 min, 4 min and 6 min in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy (AFM) and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.

  9. Highly reinforced, low magnetic and biaxially textured Ni-7 at.%W/Ni-12 at.%W multi-layer substrates developed for coated conductors

    International Nuclear Information System (INIS)

    Mechanically strengthened, highly cube textured Ni-7 at.%W/Ni-12 at.%W multi-layer substrates developed for coated conductors have been prepared by the advanced spark plasma sintering technique. The key innovation for developing this weakly magnetic and reinforced substrate was to use a new powder metallurgy and sintering route to bond multi-layers of Ni7W/Ni12W/Ni7W together in order to get an initial ingot, followed by the optimized cold working and annealing. Particular efforts were made in view of the optimization of the design, pressing as well as the heat treatment processes of the starting ingots to obtain a chemically gradient composite bulk, thus ensuring the subsequent cold deformation. The produced composite substrates have a strong {100} texture on Ni7W outer layers. The percentage of the biaxially orientated grains within a misorientation angle of 10 deg. is as high as 97.5%, while the length percentage of low-angle grain boundaries ranging from 2 deg. to 10 deg. in the composite substrate reaches 87.2%. Moreover, the yield strength σ0.2 of the tape approaches 333 MPa, and the saturation magnetization is substantially reduced by 81.6% at 77 K when compared to that of a commercial used Ni5W substrate

  10. Stressing academia?

    DEFF Research Database (Denmark)

    Opstrup, Niels; Pihl-Thingvad, Signe

    short of individual need while high degrees of fit will mitigate stress. The analysis is based on a stratified random sample including 2127 researchers at 64 Danish university departments and covering all main areas of research and all academic staff categories. The results show that fit with regard......Incongruences between the individual and the organizational work context are potential stressors. The present study focuses on the relationship between a complementary need-supply fit and Danish researchers’ self-perceived job stress. Strain is expected to increase as organizational supplies fall...... to “soft” dimensions as freedom and independence in the job, personal and professional development at work, and receiving peer recognition is highly significant for the researchers’ self-perceived stress-level. The better the fit is the lower stress-levels the researchers’ on average report. On the other...

  11. Approximation of properties of hyperelastic materials with use of energy-based models and biaxial tension data

    Science.gov (United States)

    Jamróz, Weronika

    2016-06-01

    The paper shows the way enrgy-based models aproximate mechanical properties of hiperelastic materials. Main goal of research was to create a method of finding a set of material constants that are included in a strain energy function that constitutes a heart of an energy-based model. The most optimal set of material constants determines the best adjustment of a theoretical stress-strain relation to the experimental one. This kind of adjustment enables better prediction of behaviour of a chosen material. In order to obtain more precised solution the approximation was made with use of data obtained in a modern experiment widely describen in [1]. To save computation time main algorithm is based on genetic algorithms.

  12. Imaging stress.

    Science.gov (United States)

    Brielle, Shlomi; Gura, Rotem; Kaganovich, Daniel

    2015-11-01

    Recent innovations in cell biology and imaging approaches are changing the way we study cellular stress, protein misfolding, and aggregation. Studies have begun to show that stress responses are even more variegated and dynamic than previously thought, encompassing nano-scale reorganization of cytosolic machinery that occurs almost instantaneously, much faster than transcriptional responses. Moreover, protein and mRNA quality control is often organized into highly dynamic macromolecular assemblies, or dynamic droplets, which could easily be mistaken for dysfunctional "aggregates," but which are, in fact, regulated functional compartments. The nano-scale architecture of stress-response ranges from diffraction-limited structures like stress granules, P-bodies, and stress foci to slightly larger quality control inclusions like juxta nuclear quality control compartment (JUNQ) and insoluble protein deposit compartment (IPOD), as well as others. Examining the biochemical and physical properties of these dynamic structures necessitates live cell imaging at high spatial and temporal resolution, and techniques to make quantitative measurements with respect to movement, localization, and mobility. Hence, it is important to note some of the most recent observations, while casting an eye towards new imaging approaches that offer the possibility of collecting entirely new kinds of data from living cells.

  13. What Is Stress Management?

    Science.gov (United States)

    ... Workplace Food and Beverage Toolkit What Is Stress Management? Updated:Jul 7,2016 What is Stress Management? ... FAQs About Stress Last reviewed - 6/2014 Stress Management • Home • How Does Stress Affect You? Introduction FAQs ...

  14. An improved exceedance theory for combined random stresses

    Science.gov (United States)

    Lester, H. C.

    1974-01-01

    An extension is presented of Rice's classic solution for the exceedances of a constant level by a single random process to its counterpart for an n-dimensional vector process. An interaction boundary, analogous to the constant level considered by Rice for the one-dimensional case, is assumed in the form of a hypersurface. The theory for the numbers of boundary exceedances is developed by using a joint statistical approach which fully accounts for all cross-correlation effects. An exact expression is derived for the n-dimensional exceedance density function, which is valid for an arbitrary interaction boundary. For application to biaxial states of combined random stress, the general theory is reduced to the two-dimensional case. An elliptical stress interaction boundary is assumed and the exact expression for the density function is presented. The equations are expressed in a format which facilitates calculating the exceedances by numerically evaluating a line integral. The behavior of the density function for the two-dimensional case is briefly discussed.

  15. Arbejdslivet - Stress

    OpenAIRE

    Abrahamian, Natalie; Bøgh Johansen, Katrine; Strand Henriksen, Nicoline; Schmidt, Cecilie; Møller, Michael; Atke Jakobsen, Simone; Fulgsig Simonsen, Mia My; Ceran, Gülcan

    2016-01-01

    The following report will evolve around the theme of stress. Our focus will be the work conditions for midwives based on the empirical data compiled by our interviews and an observation at the maternity ward at Nordsjællands Hospital in Hillerød. The academics of this report will be centered around the psychological theory by Richard S. Lazarus combined with other relevant theories regarding psychology, stress and the work conditions of the post-modernity. The purpose of this report is to exa...

  16. Stress Analysis

    DEFF Research Database (Denmark)

    Burcharth, Hans F.

    The following types of forces contribute to the stresses in a Dolos in a pack exposed to waves: 1)Gravity forces Compaction forces (mainly due to settlements, gravity and flow forces) 2) Flow forces 3) Impact forces (impacts between moving concrete blocks)......The following types of forces contribute to the stresses in a Dolos in a pack exposed to waves: 1)Gravity forces Compaction forces (mainly due to settlements, gravity and flow forces) 2) Flow forces 3) Impact forces (impacts between moving concrete blocks)...

  17. Non-linear analysis and the design of Pumpkin Balloons: stress, stability and viscoelasticity

    Science.gov (United States)

    Rand, J. L.; Wakefield, D. S.

    Tensys have a long-established background in the shape generation and load analysis of architectural stressed membrane structures Founded upon their inTENS finite element analysis suite these activities have broadened to encompass lighter than air structures such as aerostats hybrid air-vehicles and stratospheric balloons Winzen Engineering couple many years of practical balloon design and fabrication experience with both academic and practical knowledge of the characterisation of the non-linear viscoelastic response of the polymeric films typically used for high-altitude scientific balloons Both companies have provided consulting services to the NASA Ultra Long Duration Balloon ULDB Program Early implementations of pumpkin balloons have shown problems of geometric instability characterised by improper deployment and these difficulties have been reproduced numerically using inTENS The solution lies in both the shapes of the membrane lobes and also the need to generate a biaxial stress field in order to mobilise in-plane shear stiffness Balloons undergo significant temperature and pressure variations in flight The different thermal characteristics between tendons and film can lead to significant meridional stress Fabrication tolerances can lead to significant local hoop stress concentrations particularly adjacent to the base and apex end fittings The non-linear viscoelastic response of the envelope film acts positively to help dissipate stress concentrations However creep over time may produce lobe geometry variations that may

  18. Prediction of matrix-to-cell stress transfer in heart valve tissues.

    Science.gov (United States)

    Huang, Siyao; Huang, Hsiao-Ying Shadow

    2015-01-01

    Non-linear and anisotropic heart valve leaflet tissue mechanics manifest principally from the stratification, orientation, and inhomogeneity of their collagenous microstructures. Disturbance of the native collagen fiber network has clear consequences for valve and leaflet tissue mechanics and presumably, by virtue of their intimate embedment, on the valvular interstitial cell stress-strain state and concomitant phenotype. In the current study, a set of virtual biaxial stretch experiments were conducted on porcine pulmonary valve leaflet tissue photomicrographs via an image-based finite element approach. Stress distribution evolution during diastolic valve closure was predicted at both the tissue and cellular levels. Orthotropic material properties consistent with distinct stages of diastolic loading were applied. Virtual experiments predicted tissue- and cellular-level stress fields, providing insight into how matrix-to-cell stress transfer may be influenced by the inhomogeneous collagen fiber architecture, tissue anisotropic material properties, and the cellular distribution within the leaflet tissue. To the best of the authors' knowledge, this is the first study reporting on the evolution of stress fields at both the tissue and cellular levels in valvular tissue and thus contributes toward refining our collective understanding of valvular tissue micromechanics while providing a computational tool enabling the further study of valvular cell-matrix interactions.

  19. Tensile strength and internal stress determination in salt compacts by diametrical and axial compression tests

    International Nuclear Information System (INIS)

    Due to the brittle character of the material an indirect method (diametrical and axial compression testing) was adopted for tensile strength determination. Two lots of compacts were prepared from salt powder, by pressing it in steel dyes by means of a hydraulic press. For uniaxial tests, cylindrical compacts were used. Biaxial tests were done on disk-shaped compacts, each disk having a diametrical V-shaped cut on one of its plane areas. The punches used for compression tests, were designed to obtain a ratio of 1.2 between their curvature radius and sample radius. At the same time with the tensile strength, the stress intensity factor (KIC and KIIC values) has been obtained. The results obtained are in good agreement with the mechanical properties of the salt, previously reported. (Authors)

  20. Behavior of Three Metallic Alloys under Combined Axial-Shear Stresses at Elevated Temperature

    Science.gov (United States)

    Colaiuta, J. F.; Lissenden, C. J.; Lerch, B. A.

    2003-01-01

    Type 316 stainless steel, Haynes 188, and Inconel 718 samples were subjected to an axial-shear strain controlled loading history while the specimen temperature was held at 650 C to quantify the evolution of material state under a complex biaxial load path when the material is in the viscoplastic domain. Yield surfaces were constructed in the axial-shear stress plane using a sensitive, 30 x 10(exp -6)m/m, equivalent offset strain definition for the yield strain. Subsequent yield surfaces were constructed at various points along the strain path to define the material evolution. These subsequent yield surface translated, expanded, and distorted relative to the initial yield surface. Each of these very different materials exhibited components of isotropic, kinematic and distortional hardening. Furthermore, subsequent yield surfaces for each material have a very well defined front face and a poorly defined, flattened, back side.

  1. Is there a reliable and invariant set of muscle synergy during isometric biaxial trunk exertion in the sagittal and transverse planes by healthy subjects?

    Science.gov (United States)

    Sedaghat-Nejad, Ehsan; Mousavi, Seyed Javad; Hadizadeh, Maliheh; Narimani, Roya; Khalaf, Kinda; Campbell-Kyureghyan, Naira; Parnianpour, Mohamad

    2015-09-18

    It has been suggested that the central nervous system simplifies muscle control through basic units, called synergies. In this study, we have developed a novel target-matching protocol and used non-negative matrix factorization (NMF) technique to extract trunk muscle synergies and corresponding torque synergies. Isometric torque data at the L5/S1 level and electromyographic patterns of twelve abdominal and back muscles from twelve healthy participants (five females) were simultaneously recorded. Each participant performed a total number of 24 isometric target-matching tasks using 12 different angular directions and 2 levels of uniaxial and biaxial exertions. Within- and between-subject similarities were assessed by considering both the data of different pairs of participants, where the activation coefficients of one participant were used in the NMF analysis of another participant, and the Pearson's correlation coefficients (R) between muscle synergy vectors. The results showed that, for a healthy person, a set of four muscles (overall variance accounted for (VAF) of 97.9 ± 0.53%) and four corresponding torque synergies (overall VAF of 92.2 ± 3.03%) could efficiently decompose the sagittal and transverse torque planes into their main directions. Furthermore, the correlation coefficients were 0.77 ± 0.12, 0.86 ± 0.08, 0.78 ± 0.12, and 0.93 ± 0.04, for all synergies, reflecting the consistency of muscle synergies across participants. Overall, our results suggest that by taking advantage of muscle synergies we could potentially overcome the redundancy inherent to control strategies of the trunk neuromuscular system. In future studies, the synergies identified in patients with low back pain could be compared with those extracted from healthy participants towards various clinical and rehabilitation applications.

  2. Growth of thin Al{sub 2}O{sub 3} films on biaxially oriented polymer films by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Vaehae-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Kauppi, Emilia, E-mail: emilia.kauppi@vti.fi [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Sahagian, Khoren, E-mail: khoren@anasysinstruments.com [Anasys Instruments, 121 Gray Avenue, Suite 100, Santa Barbara, CA 93101 (United States); Johansson, Leena-Sisko, E-mail: leena-sisko.johansson@aalto.fi [Aalto University, School of Chemical Technology, Department of Forest Products Technology, P.O. Box 16100, FI-00076 AALTO (Finland); Peresin, Maria Soledad; Sievaenen, Jenni; Harlin, Ali [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland)

    2012-11-01

    The effects of thin film nucleation and initial growth on roughness, chemistry and thermomechanical properties of polymer film surfaces were studied. Al{sub 2}O{sub 3} was deposited onto commercial biaxially oriented polypropylene and polylactic acid films at 80 Degree-Sign C by using atomic layer deposition technique. Both substrates, especially the more hydrophobic polypropylene, showed initial growth through Al{sub 2}O{sub 3} clusters. There was a faster deposition of Al{sub 2}O{sub 3} on polylactic acid film than on polypropylene at the early stages of the Al{sub 2}O{sub 3} deposition. There were also indications of chemical interactions between polylactic acid and trimethyl aluminum used as a precursor for Al{sub 2}O{sub 3}. Changes in the thermo-mechanical properties of the polymer surfaces with Al{sub 2}O{sub 3} also evidenced the differences between the substrate polymer films. The near surface interphase formed in polylactic acid probably contributed to the strong increase and scattering in the softening temperature during the early thin film growth. - Highlights: Black-Right-Pointing-Pointer Growth of atomic layer deposited Al{sub 2}O{sub 3} at 80 Degree-Sign C was studied on commercial films. Black-Right-Pointing-Pointer Both substrate films showed early Al{sub 2}O{sub 3} growth through clusters. Black-Right-Pointing-Pointer Initial growth rate depends on the nature of the substrate film surface. Black-Right-Pointing-Pointer There were indications of chemical interactions between substrate and precursor. Black-Right-Pointing-Pointer Film thickness and chemical interactions affect thermo-mechanical properties.

  3. STRESS ECHOCARDIOGRAPHY

    OpenAIRE

    Salustri, Alessandro

    1994-01-01

    textabstractIn the studies reported in this thesis, stress echocardiography (either with exercise or with pharmacological agents) and myocardial perfusion scintigraphy have been performed in different groups of patients and in different clinical conditions. Some practical aspects on the protocols of echocardiographic tests are briefly reported

  4. Analysis of Automatic Crack Propagation Under Biaxial Loading Condition Based on Finite Element Method%基于有限元的双轴载荷状态下自动裂纹扩展分析

    Institute of Scientific and Technical Information of China (English)

    张志贤; 王生楠; 詹福宇

    2012-01-01

    利用Python脚本语言对Abaqus进行了二次开发,预测双轴载荷状态下裂纹扩展轨迹.对双轴载荷下中心带孔板的裂纹扩展进行了模拟,并与FRANC2D得到的计算结果进行比较.结果表明利用二次开发程序计算得到的裂纹扩展轨迹及其断裂参数与FRANC2D得到的结果基本一致,计算结果是可靠的;利用二次开发程序对双轴载荷状态下的进行裂纹扩展分析能够有效减少计算时间,提高计算效率.%This paper uses Python scripting language for second - development of Abaqus to predict crack propagation path under biaxial loading condition. The crack propagation of plane with a center hole under biaxial loading condition is analyzed using the second - development program and the results are compared with those obtained by FRANC2D. The conclusion is that the results based on Abaqus second- development are basically agreed with those by FRANC2D,which shows that the results by the secondary- development program are reliable. Using the program to analyze the crack propagation under biaxial loading condition can effectively reduce the computation time,improve calculation efficiency.

  5. Determination of global and local residual stresses in SOFC by X-ray diffraction

    Science.gov (United States)

    Villanova, Julie; Sicardy, Olivier; Fortunier, Roland; Micha, Jean-Sébastien; Bleuet, Pierre

    2010-02-01

    Solid Oxide Fuel Cell (SOFC) is a high-performance electrochemical device for energy conversion. A single cell is composed of five layers made of different ceramic materials: anode support, anode functional layer, electrolyte, cathode functional layer and cathode. The mechanical integrity of the cell is a major issue during its lifetime, especially for the electrolyte layer. Damage of the cells is mainly due to the high operating temperature, the "redox" behaviour of the anode and the brittleness of the involved materials. Since residual stresses are known to play a significant role in the damage evolution, it is important to determine them. For this purpose, residual stresses in an anode-supported planar SOFC were measured by X-ray diffraction. Firstly, macroscopic stresses in each phase of each layer were studied using the sin 2ψ method on a laboratory X-ray goniometer at room temperature. This technique enables the calculation of residual stress of the material from the measurement of the crystal lattice deformation. The electrolyte has been found under bi-axial compressive stress of -920 MPa. Secondly, X-ray measurements controlling depth penetration were made in the electrolyte using grazing incidence method. The results show that the stress is not homogenous in the layer. The first five micrometers of the electrolyte have been found less constrained (-750 MPa) than the complete layer, suggesting a gradient of deformation in the electrolyte from the interface with the Anode Functional Layer to the free surface. Finally, local stress measurements were made on the electrolyte layer by X-ray synchrotron radiation that allows high accuracy measurement on the (sub-) micrometer scale. Polychromatic and monochromatic beams are used to determine the complete strain tensor from grain to grain in the electrolyte. First results confirm the macroscopic stress trend of the electrolyte. These X-ray techniques at different scales will contribute to a better understanding of

  6. Comparison of computational analysis with clinical measurement of stresses on below-knee residual limb in a prosthetic socket.

    Science.gov (United States)

    Zhang, M; Roberts, C

    2000-11-01

    Interface pressures and shear stresses between a below-knee residual limb and prosthetic socket predicted using finite element analyses were compared with experimental measurements. A three-dimensional nonlinear finite element model, based on actual residual geometry and incorporating PTB socket rectification and interfacial friction/slip conditions, was developed to predict the stress distribution. A system for measuring pressures and bi-axial shear stresses was used to measure the stresses in the PTB socket of a trans-tibial amputee. The FE-predicted results indicated that the peak pressure of 226 kPa occurred at the patellar tendon area and the peak shear stress of 50 kPa at the anterolateral tibia area. Quantitatively, FE-predicted pressures were 11%, on average, lower than those measured by triaxial transducers placed at all the measurement sites. Because friction/slip conditions between the residual limb and socket liner were taken into consideration by using interface elements in the FE model, the directions and magnitudes of shear stresses match well between the FE prediction and clinical measurements. The results suggest that the nonlinear mechanical properties of soft tissues and dynamic effects during gait should be addressed in future work.

  7. Effect of stress-triaxiality on void growth in dynamic fracture of metals: a molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Seppala, E T; Belak, J; Rudd, R E

    2003-10-07

    The effect of stress-triaxiality on growth of a void in a three dimensional single-crystal face-centered-cubic (FCC) lattice has been studied. Molecular dynamics (MD) simulations using an embedded-atom (EAM) potential for copper have been performed at room temperature and using strain controlling with high strain rates ranging from 10{sup 7}/sec to 10{sup 10}/sec. Strain-rates of these magnitudes can be studied experimentally, e.g. using shock waves induced by laser ablation. Void growth has been simulated in three different conditions, namely uniaxial, biaxial, and triaxial expansion. The response of the system in the three cases have been compared in terms of the void growth rate, the detailed void shape evolution, and the stress-strain behavior including the development of plastic strain. Also macroscopic observables as plastic work and porosity have been computed from the atomistic level. The stress thresholds for void growth are found to be comparable with spall strength values determined by dynamic fracture experiments. The conventional macroscopic assumption that the mean plastic strain results from the growth of the void is validated. The evolution of the system in the uniaxial case is found to exhibit four different regimes: elastic expansion; plastic yielding, when the mean stress is nearly constant, but the stress-triaxiality increases rapidly together with exponential growth of the void; saturation of the stress-triaxiality; and finally the failure.

  8. Effect of Zirconia Thickness on the Tensile Stress of Zirconia Based All-Ceramic Restorations

    Directory of Open Access Journals (Sweden)

    Masood Shiezadeh

    2015-09-01

    Full Text Available Introduction: The purpose of the presented study was to evaluate the effect of zirconia thickness on the tensile stress of zirconia based all-ceramic restorations. Methods: Twenty zirconia disks with 10mm diameter were prepared in two groups using CAD/CAM system. The thickness of zirconia was 0.5mm in first group and 0.3mm in second group. After sintering, 0.4mm glass ceramic porcelain was applied to each disk. Then, sintering and glazing of porcelain carried out. Instron testing machine with 1mm/min crosshead speed used to evaluate the failure load of the samples. Biaxial Flexural strength standard formula employed to calculate tensile stress of specimens. Statistical analysis performed using SPSS software. Results: Although data analysis showed more maximum tensile stress in 1st group, no significant differences were found between two groups. Conclusion: Zirconia with 0.5mm and 0.3mm thicknesses cause similar tensile stress in all-ceramic restorations and thickness of these laminates could be reduced to 0.7mm.

  9. AE characteristics during stress corrosion cracking of sensitized type 304 stainless steel pipes

    International Nuclear Information System (INIS)

    The objective of this study was to get a better understanding on acoustic emission (AE) characteristics during stress corrosion cracking (SCC) processes of Type 304 stainless steel, to apply AE techniques to detection and monitoring of SCC of the type experienced with stainless steel boiling water reactor piping. SCC tests were performed on pipe specimens with 20 mm inner diameter. Before testing, all pipe specimens were solution-treated and then sensitized. The SCC tests were conducted in the circulating corrosion test equipment containing the pipe specimen under three kinds of bi-axial stresses, of which Mises equivalent stresses were kept at 172 MNm (17.5 kg/mm2). The test conditions were: the test temperature: 2250C; the concentration of chloride ion: approximately 50 ppm; the concentration of dissolved oxygen: approximately 10 ppm; the flow rate of water: 10 l/hr. Main results were: (1) the failure was caused mainly by intergranular stress corrosion cracking; (2) AE characteristics during the SCC test may be divided into three stages; (3) the most probable AE sources in the 3rd stage may be the phenomena due to the propagation of intergranular stress corrosion cracks; (4) the propagation velocity of intergranular stress corrosion cracks seems to become higher, as the hoop stress applied to the pipe specimens increases, even in the cases of the same value of Mises' equivalent stress; and (5) at the leakage due to SCC, cumulative counts, signal waveforms and peak-amplitude distributions shows a great change and the leakage is readily detectable by standard AE techniques. (author)

  10. Repetitive Stress Injuries

    Science.gov (United States)

    ... Can I Help a Friend Who Cuts? Repetitive Stress Injuries KidsHealth > For Teens > Repetitive Stress Injuries Print ... t had any problems since. What Are Repetitive Stress Injuries? Repetitive stress injuries (RSIs) are injuries that ...

  11. Stress and Mood

    Science.gov (United States)

    ... Relaxation Emotions & Relationships HealthyYouTXT Tools Home » Stress & Mood Stress & Mood Many people who go back to smoking ... story: Time Out Times 10 >> share What Causes Stress? Read full story: What Causes Stress? >> share The ...

  12. Stress and your heart

    Science.gov (United States)

    Coronary heart disease - stress; Coronary artery disease - stress ... Your body responds to stress on many levels. First, it releases stress hormones that make you breathe faster. Your blood pressure goes up. Your muscles ...

  13. Research and Test on Technology of Teamwork Biaxial Rototilling, Fertilizing and Seeding%双轴旋耕施肥播种复式作业技术研究与试验

    Institute of Scientific and Technical Information of China (English)

    朱松; 金亦富; 张瑞宏; 缪宏; 张剑峰; 陶德清

    2015-01-01

    针对秸秆全量还田对耕深的要求,分析了双轴分层旋耕技术的可行性,设计了一种双轴旋耕施肥播种复式作业机。该机采用双轴Z形阶梯状立体空间布置结构和双轴分层旋耕切土工艺,实现了深旋耕及秸秆深埋技术的突破,平均耕深大于20 cm,耕深稳定性约为90%。该机实现了深旋耕、碎土、施肥播种一次性作业,大大节省了耕作能耗和成本。%To the depth requirement in straw returning, the feasibility of biaxial rototilling is analyzed and a teamwork machine biaxial rototilling, fertilizing and seeding is designed.Two-axis adopts Z shaped and ladder three-dimensional structure, the technology of double layered cutting is adopted, the technical breakthrough of deep tillage and deep straw-buried is actualized.The average depth is more than 20 centimeters and the stability of the tilling depth is about 90%. Deep tillage, crushing soil, fertilizing and seeding are accomplished by one time, the energy consumption and the cost of farming are greatly saved.

  14. Oxidative stress

    Directory of Open Access Journals (Sweden)

    Stevanović Jelka

    2012-01-01

    Full Text Available The unceasing need for oxygen is in contradiction to the fact that it is in fact toxic to mammals. Namely, its monovalent reduction can have as a consequence the production of short-living, chemically very active free radicals and certain non-radical agents (nitrogen-oxide, superoxide-anion-radicals, hydroxyl radicals, peroxyl radicals, singlet oxygen, peroxynitrite, hydrogen peroxide, hypochlorous acid, and others. There is no doubt that they have numerous positive roles, but when their production is stepped up to such an extent that the organism cannot eliminate them with its antioxidants (superoxide-dismutase, glutathione-peroxidase, catalase, transferrin, ceruloplasmin, reduced glutathion, and others, a series of disorders is developed that are jointly called „oxidative stress.“ The reactive oxygen species which characterize oxidative stress are capable of attacking all main classes of biological macromolecules, actually proteins, DNA and RNA molecules, and in particular lipids. The free radicals influence lipid peroxidation in cellular membranes, oxidative damage to DNA and RNA molecules, the development of genetic mutations, fragmentation, and the altered function of various protein molecules. All of this results in the following consequences: disrupted permeability of cellular membranes, disrupted cellular signalization and ion homeostasis, reduced or loss of function of damaged proteins, and similar. That is why the free radicals that are released during oxidative stress are considered pathogenic agents of numerous diseases and ageing. The type of damage that will occur, and when it will take place, depends on the nature of the free radicals, their site of action and their source. [Projekat Ministarstva nauke Republike Srbije, br. 173034, br. 175061 i br. 31085

  15. The effect of stress state on zirconium hydride reorientation

    Science.gov (United States)

    Cinbiz, Mahmut Nedim

    correlating the finite element stress-state results with the spatial distribution of hydride microstructures observed within the optical micrographs for each sample. Experiments showed that the hydride reorientation was enhanced as the stress biaxiality increased. The threshold stress decreased from 150 MPa to 80 MPa when stress biaxiality ratio increased from uniaxial tension to near-equibiaxial tension. This behavior was also predicted by classical nucleation theory based on the Gibbs free energy of transformation being assisted by the far-field stress. An analysis of in situ X-ray diffraction data obtained during a thermo-mechanical cycle typical of vacuum drying showed a complex lattice-spacing behavior of the hydride phase during the dissolution and precipitation. The in-plane hydrides showed bilinear lattice expansion during heating with the intrinsic thermal expansion rate of the hydrides being observed only at elevated temperatures as they dissolve. For radial hydrides that precipitate during cooling under stress, the spacing of the close-packed {111} planes oriented normal to the maximum applied stress was permanently higher than the corresponding {111} plane spacing in the other directions. This behavior is believed to be a result of a complex stress state within the precipitating plate-like hydrides that induces a strain component within the hydrides normal to its "plate" face (i.e., the applied stress direction) that exceeds the lattice spacing strains in the other directions. During heat-up, the lattice spacing of these same "plate" planes actually contract due to the reversion of the stress state within the plate-like hydrides as they dissolve. The presence of radial hydrides and their connectivity with in-plane hydrides was shown to increase the ductile-to-brittle transition temperature during tensile testing. This behavior can be understood in terms of the role of radial hydrides in promoting the initiation of a long crack that subsequently propagates under

  16. The influence of deformation-induced residual stresses on the post-forming tensile stress/strain behavior of dual-phase steels

    Science.gov (United States)

    Hance, Brandon Michael

    It was hypothesized that, in dual-phase (DP) steels, strain partitioning between ferrite (alpha) and martensite (alpha') during deformation results in a distribution of post-deformation residual stresses that, in turn, affects the subsequent strength, work hardening behavior and formability when the strain path is changed. The post-forming deformation-induced residual stress state was expected to depend upon the microstructure, the amount of strain and the prestrain path. The primary objective of this research program was to understand the influence of deformation-induced residual stresses on the post-forming tensile stress/strain behavior of DP steels. Three commercially produced sheet steels were considered in this analysis: (1) a DP steel with approximately 15 vol. % martensite, (2) a conventional high-strength, low-alloy (HSLA) steel, and (3) a conventional, ultra-low-carbon interstitial-free (IF) steel. Samples of each steel were subjected to various prestrain levels in various plane-stress forming modes, including uniaxial tension, plane strain and balanced biaxial stretching. Neutron diffraction experiments confirmed the presence of large post-forming deformation-induced residual stresses in the ferrite phase of the DP steel. The deformation-alphainduced residual stress state varied systematically with the prestrain mode, where the principal residual stress components are proportional to the principal strain components of the prestrain mode, but opposite in sign. For the first time, and by direct experimental correlation, it was shown that deformation-induced residual stresses greatly affect the post-forming tensile stress/strain behavior of DP steels. As previously reported in the literature, the formability (residual tensile ductility) of the IF steel and the HSLA steel was adversely affected by strain path changes. The DP steel presents a formability advantage over the conventional IF and HSLA steels, and is expected to be particularly well suited for

  17. Formaldehyde stress

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Formaldehyde,one of the most toxic organic compounds,is produced and processed in human cells.The level of human endogenous formaldehyde is maintained at a low concentration(0.01-0.08 mmol L-1 in blood) under physiological conditions,but the concentration increases during ageing(over 65 years old).Clinical trials have shown that urine formaldehyde concentrations are significantly different between elderly Alzheimer’s patients(n=91) and normal elderly volunteers(n=38)(P<0.001).Abnormally high levels of intrinsic formaldehyde lead to dysfunction in cognition such as learning decline and memory loss.Excess extracellular and intracellular formaldehyde could induce metabolic response and abnormal modifications of cellular proteins such as hydroxymethylation and hyperphosphorylation,protein misfolding,nuclear translocation and even cell death.This cellular response called formaldehyde stress is dependent upon the concentration of formaldehyde.Chronic impairments of the brain resulted from formaldehyde stress could be one of the mechanisms involved in the process of senile dementia during ageing.

  18. Apparatus for measuring local stress of metallic films, using an array of parallel laser beams during rapid thermal processing

    International Nuclear Information System (INIS)

    The novel apparatus described here was developed to investigate the thermo-mechanical behavior of metallic films on a substrate by acquiring the wafer curvature. It comprises an optical module producing and measuring an array of parallel laser beams, a high resolution scanning stage, a rapid thermal processing (RTP) chamber and several accessorial gas control modules. Unlike most traditional systems which only calculate the average wafer curvature, this system has the capability to measure the curvature locally in 30 ms. Consequently, the real-time development of biaxial stress involved in thin films can be fully captured during any thermal treatments such as temperature cycling or annealing processes. In addition, the multiple parallel laser beam technique cancels electrical, vibrational and other random noise sources that would otherwise make an in situ measurement very difficult. Furthermore, other advanced features such as the in situ acid treatment and active cooling extend the experimental conditions to provide new insights into thin film properties and material behavior

  19. Apparatus for measuring local stress of metallic films, using an array of parallel laser beams during rapid thermal processing

    Science.gov (United States)

    Huang, R.; Taylor, C. A.; Himmelsbach, S.; Ceric, H.; Detzel, T.

    2010-05-01

    The novel apparatus described here was developed to investigate the thermo-mechanical behavior of metallic films on a substrate by acquiring the wafer curvature. It comprises an optical module producing and measuring an array of parallel laser beams, a high resolution scanning stage, a rapid thermal processing (RTP) chamber and several accessorial gas control modules. Unlike most traditional systems which only calculate the average wafer curvature, this system has the capability to measure the curvature locally in 30 ms. Consequently, the real-time development of biaxial stress involved in thin films can be fully captured during any thermal treatments such as temperature cycling or annealing processes. In addition, the multiple parallel laser beam technique cancels electrical, vibrational and other random noise sources that would otherwise make an in situ measurement very difficult. Furthermore, other advanced features such as the in situ acid treatment and active cooling extend the experimental conditions to provide new insights into thin film properties and material behavior.

  20. Stress and Reliability Analysis of a Metal-Ceramic Dental Crown

    Science.gov (United States)

    Anusavice, Kenneth J; Sokolowski, Todd M.; Hojjatie, Barry; Nemeth, Noel N.

    1996-01-01

    Interaction of mechanical and thermal stresses with the flaws and microcracks within the ceramic region of metal-ceramic dental crowns can result in catastrophic or delayed failure of these restorations. The objective of this study was to determine the combined influence of induced functional stresses and pre-existing flaws and microcracks on the time-dependent probability of failure of a metal-ceramic molar crown. A three-dimensional finite element model of a porcelain fused-to-metal (PFM) molar crown was developed using the ANSYS finite element program. The crown consisted of a body porcelain, opaque porcelain, and a metal substrate. The model had a 300 Newton load applied perpendicular to one cusp, a load of 30ON applied at 30 degrees from the perpendicular load case, directed toward the center, and a 600 Newton vertical load. Ceramic specimens were subjected to a biaxial flexure test and the load-to-failure of each specimen was measured. The results of the finite element stress analysis and the flexure tests were incorporated in the NASA developed CARES/LIFE program to determine the Weibull and fatigue parameters and time-dependent fracture reliability of the PFM crown. CARES/LIFE calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/Or proof test loading. This program is an extension of the CARES (Ceramics Analysis and Reliability Evaluation of Structures) computer program.

  1. Research opportunities and facilities at ORNL`s residual stress user center

    Energy Technology Data Exchange (ETDEWEB)

    Hubbard, C.R.; Watkins, T.R.; Kozaczek, K.; Wang, X.-L.; Spooner, S.

    1994-09-01

    The High Temperature Materials Laboratory (HTML) User Program at ORNL was established to help solve high-temperature materials problems that limit the efficiency and reliability of advanced energy-conversion systems. Both proprietary and nonproprietary research can be conducted within the user program. The facilities are open to researchers in US industry, universities, and federal laboratories. The Residual Stress User Center (RSUC), one of the six HTML user centers, was recently established and consists of two high precision x-ray diffraction systems for measurement of residual strain and texture. Both biaxial and triaxial residual strain data can be collected. Attachments to the diffraction system include a position sensitive detector and a laser specimen positioning system. The RSUC has capabilities for electropolishing and strain measurement with strain gauges. A complementary neutron diffraction facility has recently been developed and demonstrated at the High Flux Isotope Reactor at ORNL. The neutron diffraction facility enables mapping of macro residual stresses throughout the volume of a component, complementing the near surface stress measurements available by x-ray diffraction. The neutron facility has been proposed as an addition to the RSUC.

  2. Managing Leadership Stress

    CERN Document Server

    Bal, Vidula; McDowell-Larsen, Sharon

    2011-01-01

    Everyone experiences stress, and leaders face the additional stress brought about by the unique demands of leadership: having to make decisions with limited information, to manage conflict, to do more with less . . . and faster! The consequences of stress can include health problems and deteriorating relationships. Knowing what signs of stress to look for and having a strategy for increasing your resources will help you manage leadership stress and be more effective over a long career.Table of ContentsThe Stress of Leadership 7Why Is Leadership Stressful? 8Stress Assessment 13When Stress Is Wh

  3. STUDY ON BIAXIAL BENDING BEHAVIOR OF STEEL-CONCRETE COMPOSITE SHEAR WALLS%双钢板混凝土组合剪力墙双向压弯性能研究

    Institute of Scientific and Technical Information of China (English)

    可飞; 郭全全; 赵唯以; 周耀

    2016-01-01

    Based on the fiber section analysis, a biaxial bending nonlinear analysis program for steel-concrete shear walls was developed.The accuracy of the program was verified by comparisons of the existing experimental results with the finite element analysis results.Based on the nonlinear analysis method, the biaxial bending bearing capacity of steel-concrete shear walls was calculated, and the results indicated that the in-plane bearing capacity of steel-concrete shear walls decreased obviously due to the effects of external bending moment.Only considering the in-plane bearing capacity would overestimate the bearing capacity when steel-concrete shear walls was under biaxial bending state.Besides, the nonlinear analysis program was employed to study the effects of eccentric angle, eccentricity, concrete compressive strengths and steel ratios on the bearing capacity of steel-concrete shear walls.%基于纤维模型法,编制双钢板混凝土组合剪力墙(以下简称组合剪力墙)的双向压弯非线性分析程序,通过与已有试验结果、有限元计算结果的对比,验证分析程序的准确性.基于分析程序重点对组合剪力墙的双向压弯承载力进行数值计算,计算结果表明:面外弯矩的存在将显著降低组合剪力墙的面内承载能力,当组合剪力墙处于双向压弯受力状态时,完全按照面内承载进行设计将严重高估构件的承载能力.同时,利用分析程序对组合剪力墙进行参数分析,讨论荷载偏心角、荷载偏心距、混凝土强度和含钢率对组合剪力墙承载力的影响.

  4. Phase transformations and residual stresses in environmental barrier coatings

    Science.gov (United States)

    Harder, Bryan J.

    Silicon-based ceramics (SiC, Si3N4) are promising materials for high-temperature structural applications in turbine engines. However, the silica layer that forms on these materials is susceptible to attack from water vapor present in combustion environments. To protect against this degradation, environmental barrier coatings (EBCs) were developed to protect the underlying substrate. In the case of silicon carbide (SiC), multilayer coating systems consist of a Ba1-xSrxAl2Si 2O8 (BSAS) topcoat, a mullite or mullite + SrAl2Si 2O8 (SAS) interlayer, and a silicon bond coat. In this work, biaxial strains were measured on as-sprayed and heat-treated samples to analyze the stress and phase evolution in the coating system as a function of depth and temperature. Models were used to compare the results with an ideal coating system. In the assprayed state, tensile stresses as high as 175 MPa were measured, and cracking was observed. After thermally cycling the samples, stresses were significantly reduced and cracks in the topcoat had closed. The addition of SAS to the interlayer increased the compressive stress in the BSAS topcoat in thermally-cycled samples, which was desirable for EBC applications. The BSAS topcoat transformed from the as-deposited hexacelsian state to the stable celsian above 1200°C. This phase transformation is accompanied by a CTE reduction. The kinetics of the hexacelsian-to-celsian transformation were quantified for freestanding plasma-sprayed BSAS. Activation energies for bulk bars and crushed powder were determined to be ˜340 kJ/mol and ˜500 kJ/mol, respectively. X-ray diffraction and electron backscatter diffraction were used to establish how microstructural constraints reduce the transformation energy. Barrier coating lifetime and stability are also influenced by exposure to reactive, low-melting point calcium-magnesium-aluminosilicate (CMAS) deposits formed from dust and sand. Multilayer doped aluminosilicate coatings and bulk BSAS material were

  5. Stress and Heart Health

    Science.gov (United States)

    ... Recognition & Awards Healthy Workplace Food and Beverage Toolkit Stress and Heart Health Updated:Jun 13,2014 When ... Health and Heart Health Last reviewed 6/2014 Stress Management • Home • How Does Stress Affect You? Introduction ...

  6. Stress urinary incontinence

    Science.gov (United States)

    ... of urine - stress incontinence; Urinary leakage - stress incontinence; Pelvic floor - stress incontinence ... The bladder and urethra are supported by the pelvic floor muscles. Urine flows from your bladder through your ...

  7. Stress and Migraine

    Science.gov (United States)

    ... disabling headaches . Home > Stress and Migraine Print Email Stress and Migraine ACHE Newsletter Sign up for our newsletter by entering your e-mail address below. Stress and Migraine Mia Minen, MD MPH Key Points: ...

  8. Stress and Coping with Stress in Adolescence

    OpenAIRE

    Petra Dolenc

    2015-01-01

    Because of the many developmental changes in adolescence, young people are exposed to greater likelihood of experiencing stress. On the other hand, this period is critical for developing effective and constructive coping strategies. In the contribution, we summarize part of what is known about stress, stress responses and coping. Throughout, we focus on common stressful events among adolescents and emphasize the importance of dealing successfully with stressors in their daily lives. Finally, ...

  9. Stress Management

    OpenAIRE

    Prof.Univ. Dr. Paul Marinescu

    2007-01-01

    Η παρούσα διατριβή ασχολείται με το stress management και κατ’ επέκταση με το ρόλο που αναλαμβάνει να παίξει το τμήμα της Διοίκησης Ανθρωπίνων Πόρων (HRM), το πλέον υπεύθυνο τμήμα για την διεκπεραίωση τέτοιων καταστάσεων, όταν διάφοροι παράγοντες, εντός και εκτός εργασιακού χώρου, προκαλούν stress στους εργαζόμενους μιας επιχείρησης / ενός οργανισμού. Επικεντρώνει την προσοχή στην συμβολή του τμήματος HR σε μια επιχείρηση, ενώ γίνεται μια αναφορά στους διάφορους ρόλους που καλείται να αναλάβ...

  10. Teacher Wellness: Too Stressed for Stress Management?

    Science.gov (United States)

    Kipps-Vaughan, Debi; Ponsart, Tyler; Gilligan, Tammy

    2012-01-01

    Healthier, happier teachers promote healthier, happier, and more effective learning environments. Yet, many teachers experience considerable stress. Studies have found that between one fifth and one fourth of teachers frequently experience a great deal of stress (Kyriacou, 1998). Stress in teaching appears to be universal across nations and…

  11. Prenatal Maternal Stress Programs Infant Stress Regulation

    Science.gov (United States)

    Davis, Elysia Poggi; Glynn, Laura M.; Waffarn, Feizal; Sandman, Curt A.

    2011-01-01

    Objective: Prenatal exposure to inappropriate levels of glucocorticoids (GCs) and maternal stress are putative mechanisms for the fetal programming of later health outcomes. The current investigation examined the influence of prenatal maternal cortisol and maternal psychosocial stress on infant physiological and behavioral responses to stress.…

  12. Stress Management in Organizations

    OpenAIRE

    Roxana Capotescu

    2008-01-01

    Employee stress has increasingly become a concern for many organizations. Although it is not possible to eliminate stress entirely, people can learn to manage it. Many organizations have adopted occupational stress management programs to try and reduce the stress levels of their workforce. The high cost of work stress related problems highlights the need to spend more time evaluating work stress interventions and publishing the findings so that other organizations can gain insight into progra...

  13. The effect of academic stress and attachment stress on stress-eaters and stress-undereaters.

    Science.gov (United States)

    Emond, Michael; Ten Eycke, Kayla; Kosmerly, Stacey; Robinson, Adele Lafrance; Stillar, Amanda; Van Blyderveen, Sherry

    2016-05-01

    It is well established that stress is related to changes in eating patterns. Some individuals are more likely to increase their overall food intake under conditions of stress, whereas others are more likely to consume less food when stressed. Attachment style has been linked to disordered eating and eating disorders; however, comparisons of eating behaviors under attachment versus other types of stress have yet to be explored. The present laboratory study examined the eating patterns in self-identified stress-undereaters and stress-eaters under various types of stress. More specifically, the study examined the effects of academic and attachment stress on calorie, carbohydrate and sugar consumption within these two groups. Under the guise of critiquing student films, university students viewed either one of two stress-inducing videos (academic stress or attachment stress, both designed to be emotionally arousing) or a control video (designed to be emotionally neutral), and their food intake was recorded. Results demonstrated that the video manipulations were effective in inducing stress. Differential patterns of eating were noted based on group and stress condition. Specifically, stress-undereaters ate fewer calories, carbohydrates and sugars than stress-eaters in the academic stress condition, but not in the attachment stress or control condition. Findings suggest that specific types of stressors may influence eating behaviors differently.

  14. Stress og insomni

    DEFF Research Database (Denmark)

    Jennum, Poul; Zachariae, Bobby

    2012-01-01

    Insomnia and stress are two conditions, which are strongly associated and appear to be pathophysiologically integrated: the occurrence of stress increases the risk of insomnia, insomnia exacerbates stress, and coexistence of both factors has a negative influence on their prognosis. Stress...

  15. Fact Sheet on Stress

    Science.gov (United States)

    ... items) NIMH (7 items) Share Fact Sheet on Stress Download PDF Download ePub Q&A on Stress for Adults: How it affects your health and ... to avoid more serious health effects. What is stress? Stress can be defined as the brain's response ...

  16. STRESS MANAGEMENT PRACTICES & TIPS

    OpenAIRE

    UDAYSINH MANEPATIL

    2013-01-01

    Everyday, in every walk of life, We come across stress. As much as people wishfor stress free life. Such a task would be impossible to achieve. Stress is part and parcel ofour lives. Contemporary stress tends to be even more pervasive, persistence andinsidious.

  17. Stress in Bangladeshi Bengoli.

    Science.gov (United States)

    Alam, Samsul

    This report discusses the stress patterns of Bengali as spoken in Bangladesh. One of the findings indicate that every word has stress in the first syllable, with additional stress in the first syllable of the first word of the phrase. The Bengali language does not have penultimate and antepenultimate stress. Because there is no rule for changing…

  18. Stress and eating behavior

    OpenAIRE

    Peters, Achim; Langemann, Dirk

    2010-01-01

    How stress, the stress response, and the adaptation of the stress response influence our eating behavior is a central question in brain research and medicine. In this report, we highlight recent advances showing the close links between eating behavior, the stress system, and neurometabolism.

  19. Stress Management in Organizations

    Directory of Open Access Journals (Sweden)

    Roxana Capotescu

    2008-01-01

    Full Text Available Employee stress has increasingly become a concern for many organizations. Although it is not possible to eliminate stress entirely, people can learn to manage it. Many organizations have adopted occupational stress management programs to try and reduce the stress levels of their workforce. The high cost of work stress related problems highlights the need to spend more time evaluating work stress interventions and publishing the findings so that other organizations can gain insight into programs of merit. This article explore the three major approaches in stress management – primary, secondary and tertiary prevention and outline the importance of an evidence-based approach to stress management interventions. It is argued that an evidencebased approach will lead to advances in intervention practices. We also outline recommendations regarding planning and interpreting occupational stress management research in order to improve stress management interventions.

  20. Stress and work performance

    OpenAIRE

    Pajer, Zdeněk

    2011-01-01

    The thesis focuses on questions of stress and its boundless consequences on individuals and society. The theoretical part helps us to understand and to become familiar with the topic. This part is based on literature review of new studies in the field of stress , studies of coping with stress, on physiological and chemical processes during a stress situation ,on the influence of individuality of certain individual on stress load, on the society and the impact on workers' performance. Subchapt...

  1. Stress og aldring

    DEFF Research Database (Denmark)

    Jørgensen, Anders; Jørgensen, Martin Balslev; Poulsen, Henrik Enghusen

    2012-01-01

    Accumulating evidence supports the popular notion that psychological stress states may accelerate aging. Stress has been shown to influence cellular systems known to be involved in the aging process. Furthermore, stress is associated with an increased risk of various age-related medical disorders....... These effects are likely mediated by the secretion of stress hormones. In this short review we focus on biochemical and epidemiological evidence for a link between stress and aging....

  2. Stress removal and stress addition in Spanish

    OpenAIRE

    Hualde, José Ignacio

    2007-01-01

    In Spanish function words and expressions can be classified as lexically stressed or unstressed. Unstressed function words are usually realized without word-level prominence. There is also a contrast between compounds with stress on all their components and compound with a single stress, on the last member. Both in the case of function words and in the case of compounds, the facts are idiosyncratic in some respects. In this paper, these facts are presented in some detail and an analysis along...

  3. Effect of laser shock peening on residual stress and fatigue life of clad 2024 aluminium sheet containing scribe defects

    Energy Technology Data Exchange (ETDEWEB)

    Dorman, M. [Department of Aerospace Engineering, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom); Toparli, M.B. [Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Smyth, N.; Cini, A. [Department of Materials, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom); Fitzpatrick, M.E. [Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Irving, P.E., E-mail: p.e.irving@cranfield.ac.uk [Department of Materials, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom)

    2012-06-30

    Highlights: Black-Right-Pointing-Pointer Effect of laser peen intensity on local residual stress fields in 2024 aluminium. Black-Right-Pointing-Pointer Peening induces significant changes in surface topography and local hardness. Black-Right-Pointing-Pointer Residual stress at peen spot centre in tension, spot overlap in compression. Black-Right-Pointing-Pointer Notched fatigue lives increased; crack morphology correlated to residual stress field. Black-Right-Pointing-Pointer Large peening power densities can cause fatigue life reduction in notched samples. - Abstract: Laser peening at a range of power densities has been applied to 2 mm-thick sheets of 2024 T351 aluminium. The induced residual stress field was measured using incremental hole drilling and synchrotron X-ray diffraction techniques. Fatigue samples were subjected to identical laser peening treatments followed by scribing at the peen location to introduce stress concentrations, after which they were fatigue tested. The residual stresses were found to be non-biaxial: orthogonal to the peen line they were tensile at the surface, moving into the desired compression with increased depth. Regions of peen spot overlap were associated with large compression strains; the centre of the peen spot remaining tensile. Fatigue lives showed moderate improvement over the life of unpeened samples for 50 {mu}m deep scribes, and slight improvement for samples with 150 {mu}m scribes. Use of the residual stress intensity K{sub resid} approach to calculate fatigue life improvement arising from peening was unsuccessful at predicting the relative effects of the different peening treatments. Possible reasons for this are explored.

  4. Stress and Coping with Stress in Adolescence

    Directory of Open Access Journals (Sweden)

    Petra Dolenc

    2015-12-01

    Full Text Available Because of the many developmental changes in adolescence, young people are exposed to greater likelihood of experiencing stress. On the other hand, this period is critical for developing effective and constructive coping strategies. In the contribution, we summarize part of what is known about stress, stress responses and coping. Throughout, we focus on common stressful events among adolescents and emphasize the importance of dealing successfully with stressors in their daily lives. Finally, we highlight the most frequently used instruments to measure coping behaviour in youth and present an overview of the research findings on differences in coping among adolescents according to age and gender.

  5. Inelastic stress-strain response of 2[1]/[4]Cr-1Mo steel under combined tension-torsion at 600 C

    International Nuclear Information System (INIS)

    The results of the third-phase activity of the Subcommittee on Inelastic Analysis and Life Prediction of High Temperature Materials, JSMS, are summarized in this series of papers.As the first part, the evaluation of inelastic constitutive models under plasticity-creep interaction conditions is presented in extension of the previous report of the phase 2 activity. Seven types of experiment were performed under multiaxial loading of tension and torsion with normalized and tempered 2[1]/[4]Cr-1Mo steel at 600 C: (i) step-up/down creep, (ii) uniaxial tension with strain rate change, (iii) cruciform stressing, (iv) biaxial mechanical ratcheting, (v) cyclic torsion, (vi) in-phase cyclic straining and (vii) out-of-phase cyclic straining. The experimental results of these benchmark tests are compared with the simulated results by seven types of constitutive models to evaluate their accuracy in simulating the experimental behaviour of the material. ((orig.))

  6. Stress at Work Place

    OpenAIRE

    Mohammad A. Shahrour

    2010-01-01

    One of hardest forms of stresses to avoid is that work place or job stress Job stress refers to stress experienced by an individual at or because of issues at their work place The term work related stress has many meanings and it causes different levels of anxiety. Not all challenges at work can be called stress as some of these challenges drive employees upward, and empower them to learn new skills or push them to work harder to achieve a certain goal. So, this type of challenges cannot be c...

  7. Voltage controlled biaxial strain in VO{sub 2} films grown on 0.72Pb(Mg{sub 1∕3}Nb{sub 2∕3})-0.28PbTiO{sub 3} crystals and its effect on the transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Petraru, A., E-mail: apt@tf.uni-kiel.de; Soni, R.; Kohlstedt, H. [Nanoelektronik, Technische Fakultät, Christian-Albrechts-Universität zu Kiel, Kiel 24143 (Germany)

    2014-09-01

    Vanadium oxide thin films (VO{sub 2}) were deposited on 0.72Pb(Mg{sub 1∕3}Nb{sub 2∕3})-0.28PbTiO{sub 3} (PMN-PT) crystalline substrates using pulsed laser deposition method. Due to their huge piezoelectric coefficients in the order of 2500 pm/V, the PMN-PT substrates are used to impose additional amount of biaxial strain to the VO{sub 2} films by applying an external bias to the substrates. The influence of the biaxial strain on the transition temperature and on the conductive properties of the VO{sub 2} films is investigated in this work. Thus, a change in the biaxial strain of −0.8 × 10{sup −3} applied in the (110) plane of the rutile cell of the VO{sub 2} lowered the metal-to-insulator transition temperature by 1.35 °C.

  8. Determination of global and local residual stresses in SOFC by X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Villanova, Julie, E-mail: julie.villanova@cea.f [CEA Grenoble, LITEN/DTH/LCPEM, 17, rue des Martyrs, F-38054 Grenoble Cedex 9 (France); Ecole des Mines de Saint-Etienne, Centre SMS, UMR CNRS 5146, 158 cours Fauriel, F-42023 Saint-Etienne Cedex 2 (France); Sicardy, Olivier [CEA Grenoble, LITEN/DTH/LCPEM, 17, rue des Martyrs, F-38054 Grenoble Cedex 9 (France); Fortunier, Roland [Ecole des Mines de Saint-Etienne, Centre SMS, UMR CNRS 5146, 158 cours Fauriel, F-42023 Saint-Etienne Cedex 2 (France); Micha, Jean-Sebastien [CEA Grenoble/INAC/UMR5819/SprAM, 17, rue des Martyrs, F-38054 Grenoble Cedex 9 (France); Bleuet, Pierre [CEA Grenoble/INAC/SP2M, 17, rue des Martyrs, F-38054 Grenoble Cedex 9 (France)

    2010-02-15

    Solid Oxide Fuel Cell (SOFC) is a high-performance electrochemical device for energy conversion. A single cell is composed of five layers made of different ceramic materials: anode support, anode functional layer, electrolyte, cathode functional layer and cathode. The mechanical integrity of the cell is a major issue during its lifetime, especially for the electrolyte layer. Damage of the cells is mainly due to the high operating temperature, the 'redox' behaviour of the anode and the brittleness of the involved materials. Since residual stresses are known to play a significant role in the damage evolution, it is important to determine them. For this purpose, residual stresses in an anode-supported planar SOFC were measured by X-ray diffraction. Firstly, macroscopic stresses in each phase of each layer were studied using the sin{sup 2}psi method on a laboratory X-ray goniometer at room temperature. This technique enables the calculation of residual stress of the material from the measurement of the crystal lattice deformation. The electrolyte has been found under bi-axial compressive stress of -920 MPa. Secondly, X-ray measurements controlling depth penetration were made in the electrolyte using grazing incidence method. The results show that the stress is not homogenous in the layer. The first five micrometers of the electrolyte have been found less constrained (-750 MPa) than the complete layer, suggesting a gradient of deformation in the electrolyte from the interface with the Anode Functional Layer to the free surface. Finally, local stress measurements were made on the electrolyte layer by X-ray synchrotron radiation that allows high accuracy measurement on the (sub-) micrometer scale. Polychromatic and monochromatic beams are used to determine the complete strain tensor from grain to grain in the electrolyte. First results confirm the macroscopic stress trend of the electrolyte. These X-ray techniques at different scales will contribute to a better

  9. Stress in childhood

    Science.gov (United States)

    ... for children. Medical treatments produce even greater stress. Recognition of parental stress (such as divorce or financial ... ask questions) Anger Crying Whining Inability to control emotions Aggressive behavior Stubborn behavior Regression to behaviors that ...

  10. Metatarsal stress fractures - aftercare

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/patientinstructions/000553.htm Metatarsal stress fractures - aftercare To use the sharing features on ... that connect your ankle to your toes. A stress fracture is a break in the bone that ...

  11. Understanding Child Traumatic Stress

    Science.gov (United States)

    ... Public Awareness Sustainability Policy Issues Understanding Child Traumatic Stress Page Contents: Responding to Danger When Danger Turns ... malevolence, and human accountability. Back to Top Posttraumatic Stress Responses For reasons that are basic to survival, ...

  12. Coping with College Stress

    Science.gov (United States)

    ... gov/news/fullstory_160792.html Coping With College Stress Parents can help make the transition easier for ... 5, 2016 MONDAY, Sept. 5, 2016 (HealthDay News) -- Stress and anxiety are common among new college students, ...

  13. Cultural Stress Revisited

    Institute of Scientific and Technical Information of China (English)

    Hastings; K; Shula; Aizhong; Liu

    2011-01-01

    Cultural stress is no longer a rare phenomenon because the world has been reduced to the size of a village due to modern technology and advancements. It is a concept that grows in magnitude each year. More and more people are affected. In this paper, we discuss the assessment of cultural stress by combining some instruments like the Perceived Stress Scale, the Depression Anxiety, and Stress Scale with the Cultural Stress Scale. They appear to be valid and can be used across different cultures. We discuss the need to come up with a standard instrument for measuring cultural stress as opposed to having so many. We also outline ways of coping with cultural stress as it occurs at different stages. There is need for more research to counter the negative effects of cultural stress.

  14. The Nucleolus under Stress

    OpenAIRE

    Boulon, Séverine; Westman, Belinda J.; Hutten, Saskia; Boisvert, François-Michel; Lamond, Angus I

    2010-01-01

    Cells typically respond quickly to stress, altering their metabolism to compensate. In mammalian cells, stress signaling usually leads to either cell-cycle arrest or apoptosis, depending on the severity of the insult and the ability of the cell to recover. Stress also often leads to reorganization of nuclear architecture, reflecting the simultaneous inhibition of major nuclear pathways (e.g., replication and transcription) and activation of specific stress responses (e.g., DNA repair). In thi...

  15. Prenatal stress in pigs

    OpenAIRE

    Kranendonk, Godelieve

    2006-01-01

    Studies in many species, including humans, have demonstrated that stress during gestation can have long-term developmental, neuroendocrine, and behavioural effects on the offspring. Because pregnant sows can be subjected to regular stressful situations, it is relevant to study whether prenatal stress also affects their piglets. Glucocorticoids play an important role in affecting the fetus during prenatal stress, and therefore, a model to elevate maternal cortisol concentrations during gestati...

  16. Stress, Inflammation and Aging

    OpenAIRE

    Lavretsky, Helen; Newhouse, Paul A.

    2012-01-01

    This editorial provides a summary of the state of research on stress-related changes associated with aging and discuss how factors such as inflammation and sex steroid alterations may interact with psychosocial stress to affect the risk for mood and cognitive disturbance in older individuals. The authors provide an integrated summary of four studies reported in this issue of the journal and views on future direction in stress and aging research and interventions targeting resilience to stress.

  17. Stress og insomni

    DEFF Research Database (Denmark)

    Jennum, Poul; Zachariae, Bobby

    2012-01-01

    Insomnia and stress are two conditions, which are strongly associated and appear to be pathophysiologically integrated: the occurrence of stress increases the risk of insomnia, insomnia exacerbates stress, and coexistence of both factors has a negative influence on their prognosis. Stress...... and insomnia thus share complex interactions and the mechanisms involved are insufficiently understood but involve both psychological and physiological processes. First choice interventions involve behavioural and cognitive strategies and, to a lesser extent, pharmacological treatment....

  18. Stress, norepinephrine and depression.

    OpenAIRE

    Leonard, B E

    2001-01-01

    Stress is an important precipitant factor in depression, and the changes in various body systems that occur in depression are similar to those observed in response to stress. This paper discusses the interactions among the immune, endocrine and norepinephrine systems that are evident in patients with depression, as well as those affected by stress. Many of the stress-induced changes can be reversed by antidepressants, particularly norepinephrine reuptake inhibitors.

  19. Stress and Protists: No life without stress.

    Science.gov (United States)

    Slaveykova, Vera; Sonntag, Bettina; Gutiérrez, Juan Carlos

    2016-08-01

    We report a summary of the symposium "Stress and Protists: No life without stress", which was held in September 2015 on the VII European Congress of Protistology in partnership with the International Society of Protistologists (Seville, Spain). We present an overview on general comments and concepts on cellular stress which can be also applied to any protist. Generally, various environmental stressors may induce similar cell responses in very different protists. Two main topics are reported in this manuscript: (i) metallic nanoparticles as environmental pollutants and stressors for aquatic protists, and (ii) ultraviolet radiation - induced stress and photoprotective strategies in ciliates. Model protists such as Chlamydomonas reinhardtii and Tetrahymena thermophila were used to assess stress caused by nanoparticles while stress caused by ultraviolet radiation was tested with free living planktonic ciliates as well as with the symbiont-bearing model ciliate Paramecium bursaria. For future studies, we suggest more intensive analyses on protist stress responses to specific environmental abiotic and/or biotic stressors at molecular and genetic levels up to ecological consequences and food web dynamics. PMID:27365178

  20. Optimization of Bolt Stress

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    2013-01-01

    The state of stress in bolts and nuts with ISO metric thread design is examined and optimized. The assumed failure mode is fatigue so the applied preload and the load amplitude together with the stress concentrations define the connection strength. Maximum stress in the bolt is found at, the fillet...

  1. The price of stress

    NARCIS (Netherlands)

    Groot, W.; Maassen, van den H.

    1999-01-01

    In this paper an economic approach is taken to the analysis of work-related stress. This economic approach not only allows us to infer the monetary equivalent of stress, it also enables us to test some of the psychological theories on stress, such as the demand/control theory. Evidence is found that

  2. Control and Data Acquisition System for R500B Biaxial Centrifuge Shaker%R500B大型土工离心机双向振动台控制及数据采集系统

    Institute of Scientific and Technical Information of China (English)

    宋献慧; 侯瑜京; 梁建辉

    2012-01-01

    介绍了中国水利水电科学研究院建成的大型土工离心机双向(水平+垂直)振动台控制和数据采集系统,介绍了系统采用控制软件的基本功能、控制原理,以及操作程序等.目前已成功实现了在高速旋转的离心机中进行振动台的控制和数据采集,但随着各类不同试验的具体要求,系统功能仍需要进一步开发和完善.%The authors introduce the control and data acquisition system for the R500B biaxial (horizontal and vertical) shaker table of the IWHR (China Institute of Water Resources and Hydropower Research) Geotechnical Centrifuge. The control theory, the function of the software and the working procedures of the system are presented in this paper. This system has been successfully operated at 80 g centrifugal acceleration, and is needed to be improved to meet different requirements of experiments in the future.

  3. Analytic study of plastic instabilities during tension or compression tests on a metallic plate bi-axially loaded in its plane: symmetric and antisymmetric modes with respect to the median plane

    International Nuclear Information System (INIS)

    This report is a continuation of the thesis [23], devoted to the onset of necking plastic instabilities during tension tests on metallic plates bi-axially loaded in their plane. We are also interested here in compression tests, and in the development of antisymmetric defects with respect to the median plane of the plate. As in the thesis, we search for the dominant mode, i.e. the most unstable pair of wavelengths (λ1, λ2) in the loading plane. An approximate analytical formulation for the growth rate is proposed, especially for plane-strain tests in the absence of viscous effects, and for static tests in tension in the x1 and x2 loading directions. In that latter case, we retrieve published results [14][15]. For plane-strain tests, we show that infinitely dense networks of shear bands inclined at 45 deg. with respect to the loading direction instantaneously occur when heat softening prevails over work-hardening. (author)

  4. Flexión biaxial de las columnas esbeltas de concreto en alta resistencia y los tubos llenos de concreto bajo cargas a corto y largo plazo: II Verificación

    Directory of Open Access Journals (Sweden)

    Jose A. Rodríguez-Gutiérrez

    2014-12-01

    Full Text Available En un artículo adjunto se presenta el método analítico para calcular las respuestas, a corto y largo plazo, de las columnas esbeltas de concreto en alta resistencia (HSC y de los tubos rellenos de hormigón; con condiciones de apoyo generalizados, sometidos a cargas transversales de luz y a cargas axiales excéntricas en los extremos (causando curvatura simple o doble bajo flexión uniaxial o biaxial.Los tipos de columnas que pueden ser analizadas son: ovaladas, rectangulares, circulares, C, T, L o de cualquier sección transversal arbitraria, sólida o hueca, además, las que están hechas de tubos de acero circulares y rectangulares llenos de concreto en alta resistencia. En esta publicación se presenta la validez del método y los resultados obtenidos son comparados con otros, que han sido reportados por diferentes investigadores en la literatura técnica, con más de setenta muestras de columnas.

  5. 十字形试件双向拉深试验系统建立及加载精度分析%ESTABLISHMENT OF BIAXIAL TENSILE TEST OF CRUCIFORM SPECIMEN AND ANALYSIS OF LOADING ACCURACY

    Institute of Scientific and Technical Information of China (English)

    万敏; 洪强; 吴向东; 周贤宾

    2001-01-01

    The hardware and software systems of biaxial tensile test of cruciform specimen are built in order to study the plastic deformation behavior of sheet metal under complex loading paths. The key techniques, such as the displacement synchronous control of the same axial jaws, the proportion and non-proportion loading control for displacement and load, loading stop control based on load variation, and so on, are realized. The experiment shows that the test system has well accurate and reliable and provides the experimental basis for further research.%为了研究复杂加载路径下板料塑性变形行为,建立了十字形试件双向拉深试验硬件与软件系统,实现了同 轴两夹头的位移同步控制,位移和载荷的比例加载与非比例加载控制,以及根据载荷变化判断加载停止的控制等 关键技术。试验验证表明,所建系统具有较好的准确性和可靠性,为进一步研究提供了试验基础。

  6. A Servo-Control System for Biaxial Wheel Indoor Service Robots%一种双轴轮室内服务机器人小车伺服控制系统

    Institute of Scientific and Technical Information of China (English)

    李硕明; 陈越; 吴雄英

    2016-01-01

    基于32位ARM7微型处理器LPC2119开发移动机器人伺服控制系统,设计了适应于双轴独立驱动的移动小车伺服控制PI算法,采用PWM脉宽调速技术结合光电编码反馈来构成闭环电机伺服系统.系统方案在自主设计的室内移动机器人小车XMU-3上进行了验证,实验结果能达到室内服务机器人平台应用的控制精度要求.%This paper designs a servo-control system for mobile robots based on 32-bit ARM7 micro-proces-ser.The approach designs PI algorithm which suits biaxial wheel mobile robots servo-control system,adopting PWM speed control and utilizing light-electronic devices for feed-backing components to set up a closed motor servo-con-trol system.The system is tested on the self-designed XMU-3 indoor intelligent mobile robots vehicle,which proves to be able to match the control accuracy requirements and meet the potential application platform needs of indoor service robot.

  7. Neuropeptide Y and Stress

    Directory of Open Access Journals (Sweden)

    Murat Gulsun

    2012-03-01

    Full Text Available The neurobiological aspects of stress and coping skills has been the focus of interest for many researchers. Some of the studies has shown that there is a significant relationship among genetically variables, stress response and life events. Neuropeptide Y is one of the systems regulating the stress response. Under the prolonged or repeated trauma neuropeptide Y is released from the brain's key areas. This system shows different levels of functioning in individuals with different levels of resilience. There is particular interest in the variations of genes that encode stress-sensitive signaling molecules during gene-environment interaction. This condition may contribute to susceptibility of stress or stress resilience. Neuropeptide Y system plays a key role in the adaptation to behavioral stress. The reduced levels of neuropeptide Y have also been observed in treatment-resistant depression and posttraumatic stress disorder. Lower level of neuropeptide Y expression and dysfunctional neuropeptide Y system in response to stress and resulting decreased stress resilience could increase susceptibility to stress-related disorders.

  8. Oxidative Stress in Neurodegeneration

    Directory of Open Access Journals (Sweden)

    Varsha Shukla

    2011-01-01

    Full Text Available It has been demonstrated that oxidative stress has a ubiquitous role in neurodegenerative diseases. Major source of oxidative stress due to reactive oxygen species (ROS is related to mitochondria as an endogenous source. Although there is ample evidence from tissues of patients with neurodegenerative disorders of morphological, biochemical, and molecular abnormalities in mitochondria, it is still not very clear whether the oxidative stress itself contributes to the onset of neurodegeneration or it is part of the neurodegenerative process as secondary manifestation. This paper begins with an overview of how oxidative stress occurs, discussing various oxidants and antioxidants, and role of oxidative stress in diseases in general. It highlights the role of oxidative stress in neurodegenerative diseases like Alzheimer's, Parkinson's, and Huntington's diseases and amyotrophic lateral sclerosis. The last part of the paper describes the role of oxidative stress causing deregulation of cyclin-dependent kinase 5 (Cdk5 hyperactivity associated with neurodegeneration.

  9. Stress Literacy in Australian Adolescents

    Science.gov (United States)

    Varlow, Megan; Wuthrich, Viviana; Murrihy, Rachael; Remond, Louise; Tuqiri, Rebekka; van Kessel, Jacobine; Wheatley, Anna; Dedousis-Wallace, Anna; Kidman, Antony

    2009-01-01

    Stress literacy is a term that refers to knowledge about stress and stress management techniques. Levels of stress literacy were examined in more than nine hundred Australian adolescents by providing a short stress-management education session and assessing stress literacy using a pre-post survey design. It was found that while adolescents had a…

  10. Stress Management and Gifted Children

    Science.gov (United States)

    Patel, Vidisha A.

    2009-01-01

    Stress can affect anyone, and gifted children are no exception. Giftedness can sometimes be the cause of the stress. Perfectionism, sensitivity, and intensity are characteristics of gifted children that may exacerbate stress. Stress can be constructive. Prolonged stress, however, with no time to recover becomes detrimental. Continued stress upsets…

  11. Interoception and Stress

    Directory of Open Access Journals (Sweden)

    André eSchulz

    2015-07-01

    Full Text Available Afferent neural signals are continuously transmitted from visceral organs to the brain. Interoception refers to the processing of visceral-afferent neural signals by the central nervous system, which can finally result in the conscious perception of bodily processes. Interoception can, therefore, be described as a prominent example of information processing on the ascending branch of the brain-body axis. Stress responses involve a complex neuro-behavioral cascade, which is elicited when the organism is confronted with a potentially harmful stimulus. As this stress cascade comprises a range of neural and endocrine pathways, stress can be conceptualized as a communication process on the descending branch of the brain-body axis. Interoception and stress are, therefore, associated via the bi-directional transmission of information on the brain-body axis. It could be argued that excessive and/or enduring activation (e.g. by acute or chronic stress of neural circuits, which are responsible for successful communication on the brain-body axis, induces malfunction and dysregulation of these information processes. As a consequence, interoceptive signal processing may be altered, resulting in physical symptoms contributing to the development and/or maintenance of body-related mental disorders, which are associated with stress. In the current paper, we summarize findings on psychobiological processes underlying acute and chronic stress and their interaction with interoception. While focusing on the role of the physiological stress axes (HPA axis and autonomic nervous system, psychological factors in acute and chronic stress are also discussed. We propose a feed-forward model involving stress (in particular early life or chronic stress, as well as major adverse events, the dysregulation of physiological stress axes, altered perception of bodily sensations, and the generation of physical symptoms, which may in turn facilitate stress.

  12. Stress transmission in soil

    DEFF Research Database (Denmark)

    Lamandé, Mathieu; Schjønning, Per

    the principle behind the elasticity theory. However, if fitting the Söhne model to stress measurements in all three depths, the stresses were underestimated at 0.3 and 0.6 m depth, and overestimated at 0.9 m depth. A fit of the model based on data only at 0.3 m depth indicated that stresses were transmitted......We urgently need increased quantitative knowledge on stress transmission in real soils loaded with agricultural machinery. 3D measurements of vertical stresses under tracked wheels were performed in situ in a Stagnic Luvisol (clay content 20 %) continuously cropped with small grain cereals......). Seven load cells were inserted horizontally from a pit with minimal disturbance of soil in each of three depths (0.3, 0.6 and 0.9 m), covering the width of the wheeled area. The position of the wheel relative to the transducers was recorded using a laser sensor. Finally, the vertical stresses near...

  13. The World Stress Map

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Knowledge of the stress field in the Earth's crust is a key issue for the understanding of geodynamic processes,seismic hazard assessment, and stability of underground openings such as waste disposals, tunnels, mines or wells, and reservoir management. The World Stress Map project is a collaborative project of academia,industry and governmental organizations that aims to understand the states and sources of tectonic stresses in the Earth's crust. We present the Worm Stress Map at 1:46,000,000 scale as a result of more than two decades of international collaboration. The map reveals that the first-order pattern of stress is of plate-wide scale, indicating that plate boundary forces are the major control of the stress orientations and the tectonic regime.

  14. [Psychosocial stress and cardiology].

    Science.gov (United States)

    Houppe, Jean-Pierre

    2013-06-01

    Psychosocial stress is a major independent risk and prognostic factor of cardiovascular events. It includes psychological, sociological and socioeconomic factors. Cardiovascular diseases are important providers of psychosocial stress. The knowledge of the cerebral development throughout the time allows to a better understanding of the relationship between psychosocial stress and cardiovascular risk. Psychosocial stress leads, on top of traditional cardiovascular risk factors, to the development or to the worsening of an endothelial dysfunction, of an inflammatory response and prothrombotic phenomenon. Anxiolytics and antidepressors are not very effective against psychosocial stress. Physical activity and psychotherapy are much more indicated, particularly cognitve-behavioral therapy. The ESC recommends an evaluation of psychosocial stress through a short questionnaire.

  15. Stresses in Dolosse

    DEFF Research Database (Denmark)

    Burcharth, Hans F.; Liu, Zhou; Howell, Gary L.;

    1991-01-01

    Failures of rubble mound breakwaters armoured with complex types of unreinforced concrete armour units are often due to breakage. This happens when the stresses exceed the material strength. Sufficient parametric studies of the stresses are not yet available to produce design diagrams for structu......Failures of rubble mound breakwaters armoured with complex types of unreinforced concrete armour units are often due to breakage. This happens when the stresses exceed the material strength. Sufficient parametric studies of the stresses are not yet available to produce design diagrams...... for structural integrity. The paper presents the results and the analyses of model tests with 200 kg and 200 g load-cell instrumented Dolosse. Static stresses and wave generated stresses were studied as well as model and scale effects. A preliminary design diagram for Dolosse is presented as well....

  16. Role of contact couples and couple stress in the behaviour of granular media

    International Nuclear Information System (INIS)

    This paper analyses the interest of taking into account contact couples in the granular material description as well as considering the inadequacy of the micropolar description. The study is made on two types of samples: one which takes into account contact couples, and the other which does not. The response of these two media, which are submitted to a biaxial test, is analysed from both the micromechanic and macroscopic viewpoints. A numerical study which is performed on these two samples shows the influence of the presence of couples on the local static variables as well as on the macroscopic behaviour. A statistical homogenization approach is analysed to simulate the effects of couples. Due to the presence of an internal variable, a numerical study proves that this approach is relevant. This internal variable allows the taking into consideration of the influence of contact couples. A first step in the description of couples versus contact orientation is made by the introduction of the standard deviation. Finally, the inadequacy of the micropolar description which takes into account micropolar stresses is pointed out. (orig.)

  17. A three dimensional elastoplastic cyclic constitutive law with a semi discrete variable and a ratchetting stress

    International Nuclear Information System (INIS)

    The study of cyclic elastoplastic constitutive law is, at the moment, focused on non proportional loadings, but for uniaxial loadings some problems remain, as for example the ability for a law to describe simultaneously ratcheting (constant increment of strain) in non symmetrical ones. We propose a law with a discrete memory variable, the plastic strain at the last unloading, and a ratchetting stress which, in addition to previous phenomena, describes the other hand the choice of all macroscopic variables is justified by a microscopic analysis. The extension to 3D situations of this law is proposed. The discrete nature of the memory leads to discontinuity problems for some loading paths, a modification is then proposed which uses a differential evolution law. For large enough uniaxial cycles, the uniaxial law is nevertheless recovered. An incremental form of he implicit evolution problem is given, and we describe the implementation of this model in the Code Aster a thermomechanical structural software using the f.e.m. developed at Electricite de France. For a 316 stainless steel we present comparisons between experiments and numerical results in uniaxial and biaxial ratchetting and non proportional strain controlled test (circular, square, stair loading). (authors). 13 refs., 10 figs

  18. Thermal stresses in pipes

    OpenAIRE

    Al-Zaharnah, Iyad

    2002-01-01

    This study presents results about thermal stresses in externally heated pipes that are subjected to different flow types: laminar flow, turbulent flow, and pulsating flow. The effect o f flow Reynolds number on thermal stresses in the pipe is studied. To investigate the influence o f fluid and solid properties on the resulting thermal stresses in pipes, two solids namely; steel and cooper and three fluids namely; water, coolanol-25, and mercury are used in the study. Pipes with different diam...

  19. Pediatric stress fractures

    OpenAIRE

    de la Cuadra, P.; Albiñana, J.

    2000-01-01

    Stress fractures in children are uncommon. This report describes the findings of 8 cases in 6 children. One patient had 3 stress fractures: 2 consecutive midshaft stress fractures of the same tibia associated with one of the fibula. Signs and symptoms may be misdiagnosed as malignant tumors or osteomyelitis. Serial radiographs and computed tomography scans are the key to the diagnosis, although bone scan and magnetic resonance imaging can be helpful. Biopsy is unnecessary and might even be mi...

  20. The teacher under stress

    OpenAIRE

    Krnjajić Stevan B.

    2003-01-01

    Empirical records consistently point to the fact that the phenomenon of stress is characteristic of service professions, especially of teacher’s. Although stress in teachers is a problem of public interest, it is still a relatively new field of empirical investigations. Data available show that stress in teachers can have negative effects on school as an organization teacher professional achievement, his/her and his/her family psychosocial status. The most frequent symptoms of a prolonged pro...

  1. Neuropeptide Y and Stress

    OpenAIRE

    Murat Gulsun; Lut Tamam; Fatih Ozcelik

    2012-01-01

    The neurobiological aspects of stress and coping skills has been the focus of interest for many researchers. Some of the studies has shown that there is a significant relationship among genetically variables, stress response and life events. Neuropeptide Y is one of the systems regulating the stress response. Under the prolonged or repeated trauma neuropeptide Y is released from the brain's key areas. This system shows different levels of functioning in individuals with different levels of re...

  2. Stress and childhood epilepsy

    OpenAIRE

    Campen, J.S. van

    2015-01-01

    Epilepsy is one of the most common chronic diseases in childhood, characterized by the enduring predisposition to generate epileptic seizures. Children with epilepsy and their parents often report seizures precipitated by stress. In order to increase our understanding of the pathophysiological mechanisms underlying the effects of stress on seizures in childhood epilepsy, we performed a variety of studies, which are described in this thesis. In part I we evaluate the extent of stress sensitivi...

  3. Stress Among Dental Students

    OpenAIRE

    Alzahem, Abdullah

    2015-01-01

    markdownabstractAbstract Dental students are facing many stressors in dental education, causing many negative outcomes. The most common are the exams and the clinical requirements. We suggest exposing the dental students to patient care as early as possible in their curriculum. This can help to balance stress across the different years of the curriculum, and maybe reduce the stress levels in the later years of the curriculum. A study into the new Dental Education Stress Management (DESM) prog...

  4. Stress Influences on Anoikis

    OpenAIRE

    Sood, Anil K; Lutgendorf, Susan K.

    2011-01-01

    It long has been suspected that psychosocial factors affect cancer development and progression. Although the connections between stress and cancer causation are not strong, epidemiological and clinical studies have provided strong links between cancer progression and several stress-related factors including chronic stress, depression, and social isolation. Recent molecular and biological studies have identified specific signaling pathways that influence cancer growth and metastasis. In partic...

  5. Stress, Sleep, and Allergy

    OpenAIRE

    Jernelöv, Susanna

    2010-01-01

    Allergic diseases have recently increased dramatically in the western world, now affecting about 30% of the Swedish population. The reasons for this increase are unclear, but some of the suspects are behavioral factors, such as stress and sleep. Problems with stress are also common today, and stress may change the set-points for the functioning of the body, for instance in the immune system. Sleep, on the other hand, is important for recuperation, and disturbed sleep acts a ...

  6. The teacher under stress

    Directory of Open Access Journals (Sweden)

    Krnjajić Stevan B.

    2003-01-01

    Full Text Available Empirical records consistently point to the fact that the phenomenon of stress is characteristic of service professions, especially of teacher’s. Although stress in teachers is a problem of public interest, it is still a relatively new field of empirical investigations. Data available show that stress in teachers can have negative effects on school as an organization teacher professional achievement, his/her and his/her family psychosocial status. The most frequent symptoms of a prolonged professional stress are anxiety, depression, frustration, unfriendly behavior towards students and colleagues, emotional weariness, and extreme tension. Health and psychological problems cause, most frequently, the reduction of self-esteem job dissatisfaction, job resignation, absenteeism, and wrong decision-making. In an attempt to call professional public attention to negative effects of stress on the outcomes of teacher work, we have analyzed four important aspects of stress teachers experience in their everyday work (a definition and measurement of stress, (b distribution and sources of stress (problem behaviors in students, poor working conditions, lack of time, poor school ethos, (c teacher personality traits (sex, age, work experience, locus of control, job satisfaction, intention to resign absenteeism, (d strategies for overcoming and reducing negative effects of stress (direct action techniques, palliative techniques.

  7. Stress: Concepts and applications

    International Nuclear Information System (INIS)

    The stress theorem determines the stress from the electronic ground state of any quantum system with arbitrary strains and atomic displacements. We derive this theorem in reciprocal space, within the local-density-functional approximation. The evaluation of stress, force and total energy permits, among other things, the determination of complete stress-strain relations including all microscopic internal strains. We describe results of ab-initio calculations for Si, Ge, and GaAs, giving the equilibrium lattice constant, all linear elastic constants cij and the internal strain parameter ζ. (orig.)

  8. Stress and hormones

    Directory of Open Access Journals (Sweden)

    Salam Ranabir

    2011-01-01

    Full Text Available In the modern environment one is exposed to various stressful conditions. Stress can lead to changes in the serum level of many hormones including glucocorticoids, catecholamines, growth hormone and prolactin. Some of these changes are necessary for the fight or flight response to protect oneself. Some of these stressful responses can lead to endocrine disorders like Graves′ disease, gonadal dysfunction, psychosexual dwarfism and obesity. Stress can also alter the clinical status of many preexisting endocrine disorders such as precipitation of adrenal crisis and thyroid storm.

  9. Stress at Work Place

    Directory of Open Access Journals (Sweden)

    Mohammad A. Shahrour

    2010-06-01

    Full Text Available One of hardest forms of stresses to avoid is that work place or job stress Job stress refers to stress experienced by an individual at or because of issues at their work place The term work related stress has many meanings and it causes different levels of anxiety. Not all challenges at work can be called stress as some of these challenges drive employees upward, and empower them to learn new skills or push them to work harder to achieve a certain goal. So, this type of challenges cannot be considered as true stress True job stress is a condition that not only destroys employee desire to work, but also his or her energy, getting them to suffer both emotionally and physically. Warning signs of stress at work when people feel overwhelmed they feel lacking confidence, become irritated or withdrawn, less productive, less effective and their work less rewarding if these warning passed unnoticed then signs and symptoms of stress will appear. Signs and Symptoms of Excessive 4. Personal conflicts with supervisors Workplace Stress or other employees 5. Feeling insecure at work ( 1. Feeling anxious, agitated, constantly threatened with criticism depressed or apathetic or job loss 2. Loss of interest at work 6. Discrimination ( race, sex or age 3. Difficulty in attention and 7. Discouragement (to feel concentration incompetent and worthless 4. Insomnia and sleep problems 8. Sexual harassment 5. Feeling fatigue 9. Lack of flexibility in work hours 6. Muscle tension and headaches 10. Poor work environment 7. Stomach problems or different 11. Developments in technology body aches 8. Social withdrawal How to Deal with Work Place Stress 9. Loss of sex drive 10. Using alcohol or drugs to cope Fortunately, there is a lot that you can do to manage and reduce stress at work. Different Causes of Job Stress General Guidelines: 1. Poor work conditions and having no say over such conditions A. Taking responsibility for 2. Unreasonable demands from improving your

  10. STRESS IN ORGANIZATIONS

    Directory of Open Access Journals (Sweden)

    Maria-Elena, GHEORDUNESCU

    2014-11-01

    Full Text Available Taking into account the changes that are currently taking place in our country, it is clear that these changes, which occur in almost all companies, lead to new stress factors for both employees and the organization. Occupational stress is a major problem for employees and managers, but also for the whole society. The issue of stress in organizations has given birth to many debates and studies. It is a common theme that is addressed by managers, employees and consultants from different perspectives. According to a study by the European Agency for Safety and Health at Work, in the European Union, work-related stress is the second work-related health issue after dorsal disorders. It affects 28% of EU employees. The European Parliament is fully involved in addressing issues related to the psychological support of the staff. Preventing work-related stress is one of the objectives set out in the Communique of the European Commission for Employment and Social Affairs regarding their new health and safety at work strategy. Manifestations of stress in organizations are easily observable, being manifested by behaviors such as: difficulties in adapting to the changes required to work or the dramatic drop in labor productivity. Also a double action is met: both the person who passes through the stressful situation and at the organization level on which it is reflected the existence of a stressful environment. This paper aims to address the implications of workplace stress, symptoms of stress in the workplace and strategies to eliminate and prevent stress at work This paper represents an exploratory research based on qualitative methods, being consulted various sources of information: the literature, case studies, media articles, reports of relevant organizations, etc.

  11. Cyclic Testing on Rectangular Hollow Bridge Piers Under Axial Load and Biaxial Bending%双向压弯状态下矩形空心桥墩循环试验

    Institute of Scientific and Technical Information of China (English)

    韩强; 杜修力; 赵彦; 王利辉

    2013-01-01

    To investigate the seismic performance of reinforced concrete (RC) rectangular hollow bridge piers, cyclic testing on five well-confined specimens was performed under constant axial load and biaxial bending. The test variables included axial load ratio, longitudinal reinforcement ratio and lateral reinforcement ratio. The results show that these specimens are flexural failure modes; biaxial force and displacement hysteretic loops show significant stiffness and strength degradation, pinching effect and coupling interaction of the structural seismic resistances in both directions; the ductility coefficient, varying from 3. 5 to 5. 7, and the equivalent viscous damping ratio, varying from 0. 19 to 0. 26, can meet the requirements of seismic design; RC rectangular hollow bridge piers with configurations of lateral reinforcement subject to bi-directional earthquake components have excellent earthquake resistance, and can substitute for current hollow RC rectangular section configurations described in the Chinese Guideline for Seismic Design of Highway Bridges (JTG/T B02-01-2008); and the length of the plastic hinge region is found to approach one sixth of the the hollow RC rectangular bridge pier height for all specimen piers, which is far less than the currently specified minimum value in Chinese Guideline, so the length of plastic hinge region is more concentrated for RC rectangular hollow bridge piers.%为了研究水平双向地震作用下矩形空心桥墩的抗震性能,对约束良好但轴压比和纵向、横向配筋率不同的5个钢筋混凝土(RC)矩形空心桥墩在轴力和双向弯曲作用下的性能进行了循环试验研究.结果表明:试件破坏形态为桥墩底部形成塑性铰的弯曲形破坏,桥墩双向力-位移滞回曲线显示了双向压弯状态下RC矩形空心桥墩刚度和强度退化、捏拢效应以及2个水平方向抗震性能的相互影响;试件桥墩的延性系数在3.5~5.7之间,等效粘滞阻尼系数在0

  12. Experimental study on seismic behavior of Z-shaped reinforced concrete columns subjected to biaxial shearing%钢筋混凝土Z形截面双向受剪柱抗震性能试验研究

    Institute of Scientific and Technical Information of China (English)

    崔钦淑; 杨俊杰; 康谷贻

    2013-01-01

    为研究钢筋混凝土Z形截面双向受剪柱的抗震性能,对4个缩尺比为1/2的试件进行拟静力试验,分析不同水平加载方向(加载角α分别取0°、45°、90°、135°)对其抗震性能的影响,研究Z形截面柱的破坏形态,得到试件的荷载-位移滞回曲线、骨架曲线、承载力、位移延性系数、刚度退化和耗能能力等力学性能指标.研究结果表明:试件在水平反复荷载作用下的破坏形态为弯剪破坏、弯曲破坏、剪切黏结破坏和剪切斜压破坏,其中剪切破坏的试件延性较差;双向水平荷载作用方向对Z形截面柱受剪承载力的影响近似符合椭圆规律,在加载角为45°时,试件的耗能能力最强,当加载角为0°和135°时,试件的耗能能力相差不大.提出钢筋混凝土Z形截面柱双向受剪承载力的计算方法,按该方法对本次试验和已有试验共22个试件进行计算,计算结果与试验值吻合较好.%In order to study the seismic performance of Z-shaped reinforced concrete columns subjected to biaxial shearing,quasi-static tests were carried out on four 1/2 scale specimens.The effects of the horizontal loading directions (α =0°,45°,90°,135°) were studied.And the failure characteristics,mechanical behaviors of Z-shaped columns were researched.The loading-displacement hysteretic loops and skeleton curves,load bearing capacity,displacement ductility,rigidity degradation and energy dissipation capacity were analyzed.Test results indicate four types of failure patterns can be seen from the test specimens,including shear-bending failure,bending failure,shearbond failure,shear compression failure,and the shear failure ductility is very poor.It shows that the influences of the lateral bevel loads on the shear strength of Z-shaped RC frame columns can be approximately described by ellipse law.The capacity of energy dissipation is maximized in the case of 45° loading angle,and the variation is small when the

  13. Stress of stoicism

    DEFF Research Database (Denmark)

    Doan, Stacey N.; Dich, Nadya; Evans, Gary W.

    2016-01-01

    The present longitudinal study examined the combined effects of task persistence and negative emotionality (NE) on allostatic load (AL), a physiological indicator of chronic stress. In line with John Henryism theory, we hypothesized that high persistence combined with low NE may be indicative...... persistence was associated with higher physiological stress. Our results have implications for both clinical and intervention contexts....

  14. Foster Parent Stress.

    Science.gov (United States)

    Jones, Graham; Morrissette, Patrick J.

    1999-01-01

    Research findings regarding foster-parent stress and implications for counselors and counselor educators are discussed. Eleven significant themes are reported from a qualitative and quantitative study of rural foster parents (N=156). Stressful events that affect the well-being of foster parents and their relationships with children and…

  15. Videnarbejde og stress

    DEFF Research Database (Denmark)

    Buch, Anders; Andersen, Vibeke; Sørensen, Ole Henning

    . Videnarbejde kan for den enkelte være vejen til selvrealisering og begejstring, men rummer også i sig kimen til stress og udbrændthed. Og det er netop i spændingsfeltet - i kampen - mellem begejstring og belastning, at bogen ser stress i det moderne arbejdsliv, som en uoverensstemmelse mellem ydre krav og...

  16. Reynolds Stress Turbulence Model

    Directory of Open Access Journals (Sweden)

    Shuichi Torii

    1995-01-01

    the Reynolds stress in the inner wall region is substantially diminished due to the inner core movement, resulting in a decrease in the heat transfer performance, and (iii an increase in the velocity ratio of the moving inner core of the fluid flow induces a decrease in the Nusselt number as well as the Reynolds stress in the region near the inner core.

  17. Stress and Your Health

    Science.gov (United States)

    ... releasing stress hormones . These hormones make blood pressure, heart rate, and blood sugar levels go up. Long-term stress can help cause a variety of health problems, including: Mental health disorders, like depression and anxiety Obesity Heart disease High blood pressure Abnormal heart beats ...

  18. Neuropathology of stress

    NARCIS (Netherlands)

    P.J. Lucassen; J. Pruessner; N. Sousa; O.F.X. Almeida; A.M. van Dam; G. Rajkowska; D.F. Swaab; B. Czéh

    2014-01-01

    Environmental challenges are part of daily life for any individual. In fact, stress appears to be increasingly present in our modern, and demanding, industrialized society. Virtually every aspect of our body and brain can be influenced by stress and although its effects are partly mediated by powerf

  19. Leveraging Stress Level

    OpenAIRE

    Mitali PATHAK

    2011-01-01

    Stress is a costly business expense that affects both employee health and company profits. At the backdrop of this, the present research study is an attempt to explore and analysis the findings of the research studies which have been concluded in resolving and managing conflict arising through variances in stress level at the organizational hierarchy.

  20. Prenatal stress in pigs

    NARCIS (Netherlands)

    Kranendonk, Godelieve

    2006-01-01

    Studies in many species, including humans, have demonstrated that stress during gestation can have long-term developmental, neuroendocrine, and behavioural effects on the offspring. Because pregnant sows can be subjected to regular stressful situations, it is relevant to study whether prenatal stres

  1. Leveraging Stress Level

    Directory of Open Access Journals (Sweden)

    Mitali PATHAK

    2011-01-01

    Full Text Available Stress is a costly business expense that affects both employee health and company profits. At the backdrop of this, the present research study is an attempt to explore and analysis the findings of the research studies which have been concluded in resolving and managing conflict arising through variances in stress level at the organizational hierarchy.

  2. Stress, arousal, and sleep

    NARCIS (Netherlands)

    Sanford, Larry D.; Suchecki, Deborah; Meerlo, Peter; Meerlo, Peter; Benca, Ruth M.; Abel, Ted

    2015-01-01

    Stress is considered to be an important cause of disrupted sleep and insomnia. However, controlled and experimental studies in rodents indicate that effects of stress on sleep-wake regulation are complex and may strongly depend on the nature of the stressor. While most stressors are associated with

  3. Hvad er Stress?

    DEFF Research Database (Denmark)

    Strøbæk, Pernille Solveig

    2007-01-01

    I artiklen gennemgås de mest centrale historiske udviklinger inden for stressforskning og stressforståelse. Ad den historiske vej vises der frem imod stress som et righoldigt begreb med mange betydninger. Men måske har stress udviklet sig til i dag at udtrykke alt det, der opleves som galt med...

  4. Reassess the stress.

    Science.gov (United States)

    Wright, Stephen; Sayre-Adams, Jean

    The second article in our series on leadership examines stress and burnout. Nurses who are burnt out need to reassess work and relationships. Stress will pass when its cause is removed, but burnout is a 'spiritual crisis'. Self-aware, contemplative leaders are able to prevent burnout and recognise it in others.

  5. Voice Stress Analysis

    NARCIS (Netherlands)

    Rothkrantz, L.J.M.; Wiggers, P.; Wees, J.W.A. van; Vark, R.J. van

    2005-01-01

    The non-verbal content of speech carries information about the physiological and psychological condition of the speaker. Psychological stress is a pathological element of this condition, of which one of the causes is accepted to be workload. Objective, quantifiable correlates of stress are searched

  6. An all chemical solution deposition approach for the growth of highly textured CeO2 cap layers on La2Zr2O7-buffered long lengths of biaxially textured Ni-W substrates for YBCO-coated conductors

    International Nuclear Information System (INIS)

    A reel-to-reel, dip coating process has been developed to continuously deposit epitaxial La2Zr2O7 (LZO) and CeO2 on 5 m long cube-textured {100} (001)Ni tapes. Recent results for La2Zr2O7 and CeO2 buffer layers deposited on long lengths of Ni substrate for the realization of YBa2Cu3O7-x (YBCO)-coated conductors are presented. The major achievement is the development of a new all chemical solution deposition (CSD) process leading to the formation of highly textured buffer layers at moderate annealing temperatures. Reproducible highly textured, dense and crack-free LZO buffer layers and CeO2 cap layers were obtained for annealing temperatures as low as 900 deg. C in a reducing atmosphere (Ar-5 at.%-H2). The thickness of the LZO buffer layers was determined to be (200 ± 10) nm per single coating; prepared cerium oxide layers showed a thickness of 60 nm ± 10 nm. Pulsed laser deposition (PLD) was used to grow YBCO films on these substrates. A Tc0 of T = 90.5 K and ΔTc = 1.4 K was obtained on PLD-YBCO/CSD-CeO2 /CSD-LZO/Ni-5 at.% W, which shows the outstanding features of this new buffer layer architecture processed by CSD. The large layer thickness combined with low annealing temperatures is the main advantage of this new process for low-cost buffer layer deposition on Ni-RABiTS (rolling-assisted biaxially textured substrates)

  7. Overall bolt stress optimization

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    2013-01-01

    The state of stress in bolts and nuts with International Organization for Standardization metric thread design is examined and optimized. The assumed failure mode is fatigue, so the applied preload and the load amplitude together with the stress concentrations define the connection strength....... Maximum stress in the bolt is found at the fillet under the head, at the thread start, or at the thread root. To minimize the stress concentration, shape optimization is applied. Nut shape optimization also has a positive effect on the maximum stress. The optimization results show that designing a nut...... change to the bolt head and the nut has the positive indirect effect of increasing the member stiffness, all leading to a smaller joint stiffness factor....

  8. Stress corrosion cracks initiation of recrystallized Zircaloy-4 in iodine-methanol solutions

    International Nuclear Information System (INIS)

    During the pellet-cladding interaction, Zirconium-alloy fuel claddings might fail when subjected to incidental power transient in nuclear Pressurized Water Reactors, by Iodine-induced Stress Corrosion Cracking (I-SCC). This study deals with the intergranular initiation of I-SCC cracks in fully recrystallized Zircaloy-4, in methyl alcohol solution of iodine at room temperature, with the focus on critical mechanical parameters and iodine concentration. It was carried out with an approach mixing experiments and numerical simulations. An anisotropic and viscoplastic mechanical behavior model was established and validated over a wide range of loadings. With numerous constant elongation rate tensile tests and four points bending creep tests, the existence of a threshold iodine concentration I0 close to 10-6 g.g-1 was highlighted, necessary to the occurrence of I-SCC damage, along with a transition concentration I1 close to 2.10-4 g.g-1. Above I1 the mechanism changes, leading to a sped up crack initiation and a loss of sensitivity towards mechanical parameters. The importance of concentration on parameters such as crack density, crack average length and intergranular and transgranular crack velocities was evidenced. Experimental results show that plastic strain is not required for I-SCC crack initiation, if the test time is long enough in the presence of stress. Its main influence is to rush the occurrence of cracking by creating initiation sites, by way of breaking the oxide layer and building up intergranular stress. Below I1, the critical strains at initiation show a substantial strain rate sensitivity. In this domain, a threshold stress of 100 MPa was found, well below the yield stress. Thanks to the combined use of notched specimens and numerical simulations, a strong protective effect of an increasing stress bi-axiality ratio was found, both in the elastic and plastic domains. Proton-irradiated samples, up to a dose of 2 dpa, were tested in the same conditions as

  9. Effect of temperature and film thickness on microstructure and residual stress for YbBCO-coated conductors

    International Nuclear Information System (INIS)

    The rare-earth mixed oxide (Gd1-xHox)2O3 and the superconductor YbBa2Cu3O7-x were prepared by sol-gel synthesis using metal-organic precursors. Textured Gd1.802Ho0.198O3 buffer layers were grown on biaxially textured Ni (1 0 0) substrates. YbBa2Cu3O7-x layers were epitaxially grown on the Gd1.802Ho0.198O3-coated Ni substrates using the reel-to-reel sol-gel dip coating system. Different thicknesses of superconducting layers, annealed at various temperatures, were tried to observe the effects of thickness and temperature on residual stress and microstructure properties. Residual stress in the YbBCO/Gd1.802Ho0.198O3/Ni was calculated analytically. The results showed that variation of residual stress along the thickness of structure (Ni substrate, buffer layer and YbBCO film) was constant. We also observed that the Ni substrate is under tension while buffer layer was under compression in the case of without YbBCO layer. However the residual stress was under compression in the case of YbBCO in all layers. The surface morphologies and microstructure of all samples were characterized by environmental scanning electron microscope (ESEM), atomic force microscope (AFM) and X-ray diffraction (XRD). The pole figure texture analyses of Ni substrate, Gd1.802Ho0.198O3 buffer layers and YbBCO film have shown a single cube-on-cube textured structure

  10. Bolt Stress Monitor

    Science.gov (United States)

    1978-01-01

    In photo, an engineer is using a new Ultrasonic Bolt Stress Monitor developed by NASA's Langley Research Center to determine whether a bolt is properly tightened. A highly accurate device, the monitor is an important tool in construction of such structures as pressure vessels, bridges and power plants, wherein precise measurement of the stress on a tightened bolt is critical. Overtightened or undertightened bolts can fail and cause serious industrial accidents or costly equipment break-downs. There are a number of methods for measuring bolt stress. Most widely used and least costly is the torque wrench, which is inherently inaccurate; it does not take into account the friction between nut and bolt, which has an influence on stress. At the other end of the spectrum, there are accurate stress-measuring systems, but they are expensive and not portable. The battery-powered Langley monitor fills a need; it is inexpensive, lightweight, portable and extremely accurate because it is not subject to friction error. Sound waves are transmitted to the bolt and a return signal is received. As the bolt is tightened, it undergoes changes in resonance due to stress, in the manner that a violin string changes tone when it is tightened. The monitor measures the changes in resonance and provides a reading of real stress on the bolt. The device, patented by NASA, has aroused wide interest and a number of firms have applied for licenses to produce it for the commercial market.

  11. Assessment of Workplace Stress: Occupational Stress, Its Consequences, and Common Causes of Teacher Stress.

    Science.gov (United States)

    Hansen, Jo-Ida; Sullivan, Brandon A.

    This chapter introduces teachers and other education professionals to the assessment of occupational stress. It begins with a brief discussion of what occupational stress is, and overview of the consequences of prolonged stress, and a review of the common causes of teacher stress. Next, it presents methods for reducing occupational stress through…

  12. Exercise for Stress and Anxiety

    Science.gov (United States)

    ... stimulate anti-anxiety effects. Relationship of Exercise to Anxiety Disorders Stress and anxiety are a normal part of life, ... Tips Severe Storms: How to Reduce Your Anxiety Anxiety and Stress in the Workplace Exercise for Stress and Anxiety ...

  13. [Stress and allergy].

    Science.gov (United States)

    Radosević-Vidacek, Biserka; Macan, Jelena; Kosćec, Adrijana

    2004-06-01

    Stress is one of the components in the complex interaction of environmental, genetic, physiological, psychological, behavioural and social factors that can influence the body's ability to remain healthy or become healthy, to resist or overcome a disease. Stress can alter neuroendocrine and immune mechanisms of health and disease through various psychosocial processes. In addition, it can affect health through the impact on health-impairing behaviours and on compliance with medical regimens. At the same time, the relationship between stress and health is not unidirectional but bi-directional. Current views on the relation between stress and allergy vary from the denial of any relationship that could fundamentally help in allergy treatment to the widespread opinion that psychological stress can exacerbate some skin symptoms and precipitate asthma. The role of stress in the genesis, incidence and symptomatology of allergy still remains a controversial issue since the mechanisms of that relationship are not well understood. Starting from the biopsychosocial model of disease, we introduced the Social Readjustment Rating Scale which measures stressful life events, and the WHOQOL-BREF which measures subjective quality of life, into an extensive multidisciplinary study of immunotoxic effects of indoor bioaerosols and lifestyle. This paper describes the characteristics of those two questionnaires and discusses the relationship between stress and various domains of the quality of life. The Social Readjustment Rating Scale proved to be a reliable predictor for quality of life in the domains of physical health and environment. Future analyses will examine the role of stress and subjective quality of life in allergy.

  14. Indutores do stress parental

    OpenAIRE

    Costa, Catarina Andreia Campos

    2011-01-01

    Dissertação de Mestrado apresentada à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Psicologia, especialização em Clínica e da Saúde. A presente investigação tem como objectivo aprofundar o tema do stress parental, averiguando quais são os indutores do mesmo. Segundo Abdin (1992) o stress parental depende de um conjunto de factores, que funcionam como indutores de stress. Este autor considera que estes são compostos pelas característi...

  15. Basic stress analysis

    CERN Document Server

    Iremonger, M J

    1982-01-01

    BASIC Stress Analysis aims to help students to become proficient at BASIC programming by actually using it in an important engineering subject. It also enables the student to use computing as a means of learning stress analysis because writing a program is analogous to teaching-it is necessary to understand the subject matter. The book begins by introducing the BASIC approach and the concept of stress analysis at first- and second-year undergraduate level. Subsequent chapters contain a summary of relevant theory, worked examples containing computer programs, and a set of problems. Topics c

  16. Pacing stress echocardiography

    Directory of Open Access Journals (Sweden)

    Agrusta Marco

    2005-12-01

    Full Text Available Abstract Background High-rate pacing is a valid stress test to be used in conjunction with echocardiography; it is independent of physical exercise and does not require drug administration. There are two main applications of pacing stress in the echo lab: the noninvasive detection of coronary artery disease through induction of a regional transient dysfunction; and the assessment of contractile reserve through peak systolic pressure/ end-systolic volume relationship at increasing heart rates to assess global left ventricular contractility. Methods The pathophysiologic rationale of pacing stress for noninvasive detection of coronary artery disease is obvious, with the stress determined by a controlled increase in heart rate, which is a major determinant of myocardial oxygen demand, and thereby tachycardia may exceed a fixed coronary flow reserve in the presence of hemodynamically significant coronary artery disease. The use of pacing stress echo to assess left ventricular contractile reserve is less established, but promising. Positive inotropic interventions are mirrored by smaller end-systolic volumes and higher end-systolic pressures. An increased heart rate progressively increases the force of ventricular contraction (Bowditch treppe or staircase phenomenon. To build the force-frequency relationship, the force is determined at different heart rate steps as the ratio of the systolic pressure (cuff sphygmomanometer/end-systolic volume index (biplane Simpson rule. The heart rate is determined from ECG. Conclusion Two-dimensional echocardiography during pacing is a useful tool in the detection of coronary artery disease. Because of its safety and ease of repeatability noninvasive pacing stress echo can be the first-line stress test in patients with permanent pacemaker. The force-frequency can be defined as up- sloping (normal when the peak stress pacing systolic pressure/end-systolic volume index is higher than baseline and intermediate stress

  17. Stress and Health

    DEFF Research Database (Denmark)

    Rod, Naja Hulvej

    2014-01-01

    cancer. The combined evidence does not support the hypothesis of stress being an important risk factor for breast cancer incidence or recurrence. Parkinson’s disease is one of the most common neurodegenerative disorders in the elderly population, but the hypothesis that stress increases the risk...... of Parkinson’s disease is not supported in the dissertation. The experience of major life events appears, on the other hand, to be strongly associated with onset of depression, which is a common non-motor symptom of Parkinson’s disease progression. Mechanisms linking stress to health include a combination...

  18. Life Event, Stress and Illness

    OpenAIRE

    Salleh, Mohd. Razali

    2008-01-01

    The relationship between stress and illness is complex. The susceptibility to stress varies from person to person. Among the factors that influenced the susceptibility to stress are genetic vulnerability, coping style, type of personality and social support. Not all stress has negative effect. Studies have shown that short-term stress boosted the immune system, but chronic stress has a significant effect on the immune system that ultimately manifest an illness. It raises catecholamine and sup...

  19. Overcoming job stress

    Science.gov (United States)

    Job stress may be a problem for you if you have any of these signs: Frequent headaches Upset stomach Trouble sleeping Problems in your personal relationships Feeling unhappy in your job Feeling angry often ...

  20. Psychological Stress and Cancer

    Science.gov (United States)

    ... neoadjuvant chemotherapy were asked about their use of beta blockers, which are medications that interfere with certain stress ... before and during chemotherapy. Women who reported using beta blockers had a better chance of surviving their cancer ...