WorldWideScience

Sample records for biaxial stress

  1. Analysis of Biaxially Stressed Bridge Deck Plates

    DEFF Research Database (Denmark)

    Jönsson, Jeppe; Bondum, Tommi HØjer

    2012-01-01

    The ultimate state analysis of bridge deck plates at the intersection zone between main girders and transverse beams is complicated by biaxial membrane stresses, which may be in compression or tension in either direction depending on the bridge configuration and the specific location. This paper presents a detailed investigation of the ultimate capacity of simply supported plates subjected to biaxial loads. The full interaction domain of combinations of compressive and tensile loads has been investigated including a large number of imperfections. It was found that non-standard imperfection modes in parts of the interaction domain lead to more critical and lower ultimate capacity than critical buckling mode imperfections.

  2. Stress Concentrations for Slotted Plates in Bi-Axial Stress

    Directory of Open Access Journals (Sweden)

    Bahai, S. Taylor

    2012-02-01

    Full Text Available The photo-elastic method has been employed to determine stress concentration factor (SCF for square plates containing holes and inclined slots when the plate edges are subjected to in-plane tension combined with compression. Analyses given of the isochromatic fringe pattern surrounding the hole provides the SCF conveniently. The model material is calibrated from the known solution to the stress raiser arising from a small circular hole in a plate placed under biaxial tension-compression. These results also compare well with a plane stress FE analysis. Consequently, photo-elasticity has enabled SCF’s to be determined experimentally for a biaxial stress ratio, nominally equal to –4, in plates containing a long, thin slot arranged to be in alignment with each stress axis. The two, principal stresses lying along axes of symmetry in the region surrounding the notch are separated within each isochromatic fringe by the Kuske method [1]. FE provides a comparable full-field view in which contours of maximum shear stress may be identified with the isochromatic fringe pattern directly. The principal stress distributions referred to the plate axes show their maximum concentrations at the notch boundary. Here up to a fourfold magnification occurs in the greater of the two nominal stresses under loads applied to the plate edges. Thus, it is of importance to establish the manner in which the tangential stress is distributed around the slot boundary. Conveniently, it is shown how this distribution is also revealed from an isochro-matic fringe pattern, within which lie the points of maximum tension and maximum compression.

  3. Effect of Increasing Speed on Stress of Biaxial Bogie Frames

    OpenAIRE

    Ali Ziaei Asl; Farid Vakili Tahami; Mohammad Zehsaz; Fatemeh Ahmadian

    2011-01-01

    Increasing the trains’ speed has always been one of the goals of any railway industry and train manufacturers. Also, the influence of the train speed on bogie’s dynamics has an immense importance. Therefore, it is important to analyze the effect of train speed on the stress distribution in different parts of train structure. In this study the result of the increasing speed on the applied stresses of a biaxial bogie frame has been examined. For this purpose, a biaxial bogie frame has been ...

  4. Cyclic Biaxial Stress Measurement Method Using the Grain Growth Direction in Electrodeposited Copper Foil

    OpenAIRE

    Ono Yuichi; Li Cheng; Hino Daisuke

    2010-01-01

    A method that uses grain growth direction in electrodeposited copper foil to measure cyclic biaxial stress is examined in this paper. The grain growth direction is measured by image processing software after a cyclic loading test for various biaxial stress ratios is carried out. Since the grain growth occurs in two directions and its directions correspond closely with the direction of maximum shearing stress when the biaxial stress ratio is negative, the principal stress can be measured usin...

  5. Mean stress effects in biaxial fatigue of Inconel 718

    International Nuclear Information System (INIS)

    Biaxial fatigue tests were conducted on Inconel 718 thin-walled tubular specimens to quantify the effect of mean stress. The specimens were loaded in combined tension and torsion in strain control at room temperature. Fatigue lives ranged from 3000 to 15,000 cycles depending on the mean stress. These data were correlated with a parameter based on the maximum plastic shear strain amplitude, normal strain amplitude and mean normal stress on the plane of maximum shear strain amplitude. This parameter was combined with the Coffin-Manson equation for estimating fatigue lives. Observations of the cracking behavior show that mean stress affects the rate of crack growth and distribution of cracks

  6. An apparatus for measuring bi-axial stresses

    International Nuclear Information System (INIS)

    The invention relates to an apparatus for measuring biaxial stresses in a metal test-piece submitted to severe environmental conditions. An apparatus according to the invention is characterized by an outer envelope, e.g. of stainless steel, with an inner coating and a high electrical conductivity, a moving piston fixed to the test-piece and a pressurizing conduct for forming a cavity capable of resonating according two frequency-modes, said cavity being coupled to a hyper-frequency source by means of a wave-guide, frequency variations being detected for obtaining a measurement of the test piece biaxial stress. An apparatus according to the invention is suitable in particular for testing materials for nuclear reactors and caustic environments

  7. Study on thermal fatigue endurance under biaxial stress state

    International Nuclear Information System (INIS)

    The design specifications for pressure vessels permit the yield point to be exceeded considerably in the case of secondary stresses. Pressure vessel components must therefore often be designed for fatigue endurance. Dimensioning in accordance with the ASME Code has hitherto been based on uniaxial mechanical tests with emphasis on high safety factors. The influence of a multi-axial stress on the number of load cycles and the effect of thermal cycles on the course of material fatigue remain largely unclear. The recent investigations described here are aimed at determining in suitable experiments to what extent actual stresses set up by thermal cycles in a biaxial stress field are covered by the simple approach hitherto used in practice. At the same time the limitations of the materials when exposed to these complex stresses are determined. The following experiments were carried out to solve the above questions: thermal biaxial load cycle tests with carbon and austenitic steels, determination of service life as a function of the constrained strains, determination of the stress/strain curve in the form of a Bauschinger loop. Establishing the stress/strain curve is especially important since from it is derived the tangent modulus introduced in the computation of the buckling stress of components subjected to such stresses. Results are given and discussed. (author)

  8. Creep fatigue interaction on biaxially loaded structures under compressive stresses

    International Nuclear Information System (INIS)

    Creep or relaxation damage criteria for creep-fatigue interaction are poorly defined; as a result, design codes generally use the von Mises criterion, which does not take into account the hydrostatic stress level and considers both tensile and compressive stresses in the same way. Investigation of this problem requires mock-up testing with multiaxial compressive loads. This is the objective of an experimental program described in this paper: a cylinder is cyclically subjected to a high radial temperature gradient that is maintained for about five hours, resulting in biaxial compression loading on the hot skin. The experimental program is completed by interpretative analysis. (orig./RF)

  9. Cyclic Biaxial Stress Measurement Method Using the Grain Growth Direction in Electrodeposited Copper Foil

    Directory of Open Access Journals (Sweden)

    Ono Yuichi

    2010-01-01

    Full Text Available A method that uses grain growth direction in electrodeposited copper foil to measure cyclic biaxial stress is examined in this paper. The grain growth direction is measured by image processing software after a cyclic loading test for various biaxial stress ratios is carried out. Since the grain growth occurs in two directions and its directions correspond closely with the direction of maximum shearing stress when the biaxial stress ratio is negative, the principal stress can be measured using Mohr's stress circle. On the other hand, when the biaxial stress ratio is positive, above-mentioned feature does not occur. Therefore, the first principal stress can be measured based on the grain growth density. The number of grains necessary to measure the biaxial stress is estimated by a statistical approach.

  10. Hierarchical folding of elastic membranes under biaxial compressive stress

    Science.gov (United States)

    Kim, Pilnam; Abkarian, Manouk; Stone, Howard A.

    2011-12-01

    Mechanical instabilities that cause periodic wrinkling during compression of layered materials find applications in stretchable electronics and microfabrication, but can also limit an application’s performance owing to delamination or cracking under loading and surface inhomogeneities during swelling. In particular, because of curvature localization, finite deformations can cause wrinkles to evolve into folds. The wrinkle-to-fold transition has been documented in several systems, mostly under uniaxial stress. However, the nucleation, the spatial structure and the dynamics of the invasion of folds in two-dimensional stress configurations remain elusive. Here, using a two-layer polymeric system under biaxial compressive stress, we show that a repetitive wrinkle-to-fold transition generates a hierarchical network of folds during reorganization of the stress field. The folds delineate individual domains, and each domain subdivides into smaller ones over multiple generations. By modifying the boundary conditions and geometry, we demonstrate control over the final network morphology. The ideas introduced here should find application in the many situations where stress impacts two-dimensional pattern formation.

  11. 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.

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

    International Nuclear Information System (INIS)

    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 Fx and Fy 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.

  13. Polarized-cathodoluminescence study of uniaxial and biaxial stress in GaAs/Si

    Science.gov (United States)

    Rich, D. H.; Ksendzov, A.; Terhune, R. W.; Grunthaner, F. J.; Wilson, B. A.; Shen, H.; Dutta, M.; Vernon, S. M.; Dixon, T. M.

    1991-01-01

    The strain-induced splitting of the heavy-hole (hh) and light-hole (lh) valence bands for 4-microns thick GaAs/Si is examined on a microscopic scale using linear polarized-cathodoluminescence imaging and spectroscopy. The energies and intensities of the hh- and lh-exciton luminescence are quantitatively analyzed to determine spatial variations in the stress tensor. The results indicate that regions near and far from the microcracks are primarily subject to uniaxial and biaxial tensile stresses, respectively. The transition region where biaxial stress gradually converts to uniaxial stress is analyzed, and reveals a mixing of lh and hh characters in the strain-split bands.

  14. Plastic Stress-strain Relations for 75S-T6 Aluminum Alloy Subjected to Biaxial Tensile Stresses

    Science.gov (United States)

    Marin, Joseph; Ulrich, B H; Hughes, W P

    1951-01-01

    In this investigation, the material tested was a 75S-T6 aluminum alloy and the stresses were essentially biaxial and tensile. The biaxial tensile stresses were produced in a specially designed testing machine by subjecting a thin-walled tubular specimen to axial tension and internal pressure. Plastic stress-strain relations for various biaxial stress conditions were obtained using a clip-type SR-4 strain gage. Three types of tests were made: Constant-stress-ratio tests, variable-stress-ratio tests, and special tests. The constant-stress-ratio test results gave control data and showed the influence of biaxial stresses on the yield, fracture, and ultimate strength of the material. By means of the variable-stress-ratio tests, it is possible to determine whether there is any significant difference between the flow and deformation type of theory. Finally, special tests were conducted to check specific assumptions made in the theories of plastic flow. The constant-stress-ratio tests show that the deformation theory based on the octahedral, effective; or significant stress-strain relations is in approximate agreement with the test results. The variable-stress-ratio tests show that both the deformation and flow theory are in equally good agreement with the test results.

  15. Experimental study on ultimate strength and strain behavior of concrete under biaxial compressive stresses

    International Nuclear Information System (INIS)

    The purpose of this investigation was to study the ultimate strength failure mode and deformation behavior of concrete under short-term biaxial compressive stresses, as an aid to design and analyze the concrete structures subjected to multiaxial compression such as prestressed or reinforced concrete vessel structures. The experimental work on biaxial compression was carried out on the specimens of three mix proportions and different ages with 10cm x 10cm x 10cm cubic shape in a room controlled at 200C. The results are summarized as follows. (1) To minimize the surface friction between specimens and loading platens, the pads of teflon sheets coated with silicone grease were used. The coefficient of friction was measured and was 3 percent on the average. (2) The test data showed that the strength of the concrete subjected to biaxial compression increased as compared to uniaxial compressive strength, and that the biaxial strength increase was mainly dependent on the ratio of principal stresses, and it was hardly affected by mix proportions and ages. (3) The maximum increase of strength, which occurred at the stress ratio of approximately sigma2/sigma1 = 0.6, was about 27 percent higher than the uniaxial strength of concrete. (4) The ultimate strength in case of biaxial compression could be approximated by the parabolic equation. (Kako, I.)

  16. A preliminary numerical stress analysis of a dynamic biaxial testing machine

    International Nuclear Information System (INIS)

    The paper concerns a set of 2 D and 3 D stress analysis carried out by ADINA code on a cruciform specimen under static and dynamic loads. The specimen is devoted to investigate material dynamic constitutive equation by biaxial loading devices. The stress distribution resulted constant in the central area of the specimen (constant thickness), while some stress concentrations resulted in external branch elements. (orig.)

  17. Stress biaxiality in high-burnup PWR fuel cladding under reactivity-initiated accident conditions

    International Nuclear Information System (INIS)

    In order to promote a better understanding of failure mechanisms of high-burnup pressurized water reactor (PWR) fuels under reactivity-initiated accident (RIA) conditions, stress biaxiality in cladding has been estimated for the pellet-cladding (PC) mechanical interaction (PCMI) phase. The estimation was based on an analysis of the transient elongations of a pellet stack and a cladding tube measured in RIA-simulating experiments in the nuclear safety research reactor (NSRR) using the RANNS code. Stress biaxiality in the high-burnup PWR fuel cladding during the PCMI phase has been estimated to be 0.7-0.8, on average, at the mid-wall of the cladding. A comparison with fresh fuel test results and a sensitivity analysis showed that the effects of burnup and pulse width on cladding stress biaxiality are less than 10% for the investigated range. The present analysis also indicated that PC friction is strong, and that the cladding constraint on pellet stack elongation is significant irrespective of burnup. Therefore, it is recommended that strong PC friction be assumed, which is similar to the mechanical bonding condition, and that fuel pellets be treated as deformable materials in models of fuel behavior during the PCMI phase. (author)

  18. Numerical analysis of interacting cracks in biaxial stress field

    International Nuclear Information System (INIS)

    The stress corrosion cracks as seen for example in PWR steam generator tubing made of Inconel 600 usually produce highly irregular kinked and branched crack patterns. Crack initialization and propagation depends on stress state underlying the crack pattern. Numerical analysis (such as finite element method) of interacting kinked and branched cracks can provide accurate solutions. This paper discusses the use of general-purpose finite element code ABAQUS for evaluating stress fields at crack tips of interacting complex cracks. The results obtained showed reasonable agreement with the reference solutions and confirmed use of finite elements in such class of problems.(author)

  19. A new analytical model about the relationship between nominal failure stresses and porosity for foamed metals under biaxial tension

    International Nuclear Information System (INIS)

    Foamed metals have been widely used as various engineering materials, and their mechanical properties have also been drawing extensive attention. In the present paper, a new mechanical and analytical model is established for these materials with isotropic three-dimensional reticulated structure under biaxial tension, and the mathematical equation about biaxial nominal stresses is deduced for the biaxial tension at the beginning of failure of the porous body. With the relevant experiment, the relation formula is proved to be very effective. Different from the relevant theoretical system of Gibson and Ashby, the present mathematical relationship can be conveniently achieved from directly using the 'beam theory' on this mechanical and analytical model. In addition, this relationship can be further expressed as the mathematical relationship among the nominal failure 'deviatoric stress', the nominal failure 'average stress' and porosity, but the concepts of both the 'deviatoric stress' and the 'average stress' can appear just from the mathematical treatment

  20. Estimation of low cycle fatigue life of elbows considering bi-axial stress effect

    International Nuclear Information System (INIS)

    Elbow pipes are commonly used in the piping systems of power plants and chemical plants. The stress states at elbow part are complex and quite different from those of the straight pipes. It is well known that the fatigue lives of metals under simple push-pull conditions were successfully predicted by the Manson's universal slope method. However, it have been pointed out by the several researchers that the low cycle fatigue lives of elbows under combined cyclic bending and inner pressure could not be predicted by the Manson's universal slope method. However, the reasons for this are not made clear. In this work, the low cycle fatigue tests and the finite element analysis of elbows under cyclic bending and inner pressures were carried out. It was found that the bi-axial stress ratio, which is a ratio of hoop stress and axial stress, at elbows are quite high. Considering the bi-axial stress ratio, the revised Manson's universal slope method was proposed in this paper. It was shown that the low cycle fatigue lives of elbows under combined cyclic bending and inner pressure were predicted conservatively by the proposed method. (author)

  1. Microcracking of High Performance Concrete Subjected to Biaxial Tension - Compression Stresses

    Scientific Electronic Library Online (English)

    José Marcio F., Calixto.

    2002-09-01

    Full Text Available SciELO Brazil | Language: English Abstract in english The results of an experimental investigation on the microcracking of high-performance concrete subjected to biaxial tension-compression stresses are presented. Short-term static tests and microcracking mapping were performed on 12.5 cm square by 1.25 cm thick plates. Strain controlled tests were exe [...] cuted in a biaxial testing machine constructed at the University of Texas. The primary variables studied were the deformations and the ultimate stress level at each stress ratio as well as the microcracking patterns and total crack lengths. For the microcracking study, the plates, after straining, were impregnated by an epoxy and then examined under a microscope. Microcracks were classified into simple and combined cracks, since this distinction allows for a much better representation of the microcracking process. A simple crack is either a bond or mortar crack where a combined crack contains both of these. For all stress ratios tested, the stress-strain behavior was directly related to the internal microcracking pattern. In all cases, the failure was directly related to the formation and propagation of the combined cracks.

  2. Microcracking of High Performance Concrete Subjected to Biaxial Tension - Compression Stresses

    Directory of Open Access Journals (Sweden)

    José Marcio F. Calixto

    2002-09-01

    Full Text Available The results of an experimental investigation on the microcracking of high-performance concrete subjected to biaxial tension-compression stresses are presented. Short-term static tests and microcracking mapping were performed on 12.5 cm square by 1.25 cm thick plates. Strain controlled tests were executed in a biaxial testing machine constructed at the University of Texas. The primary variables studied were the deformations and the ultimate stress level at each stress ratio as well as the microcracking patterns and total crack lengths. For the microcracking study, the plates, after straining, were impregnated by an epoxy and then examined under a microscope. Microcracks were classified into simple and combined cracks, since this distinction allows for a much better representation of the microcracking process. A simple crack is either a bond or mortar crack where a combined crack contains both of these. For all stress ratios tested, the stress-strain behavior was directly related to the internal microcracking pattern. In all cases, the failure was directly related to the formation and propagation of the combined cracks.

  3. Numerical analysis of branched cracks in bi-axial stress fields

    International Nuclear Information System (INIS)

    The stress corrosion cracks as seen for example in PWR steam generator tubing made of Inconel 600 are usually found to be of highly irregular kinked and branched shapes. Numerical analysis of kinked and branched cracks in bi-axial plane stress fields using methods such as finite or boundary element method may provide useful and cost effective solutions. However, accurate analysis of complex shaped cracks requires very fine meshes and, consequently, excessively high computational efforts. This paper discusses some possible strategies of numerical modeling of kinked and branched cracks in general bi-axial stress field using the general-purpose finite element code ABAQUS. The strategies discussed include J-integral and stress intensity factor solutions with different mesh densities. The accuracy of the numerical results obtained is compared with reference solutions from the literature. The main result of the paper is an optimal numerical strategy, which maximizes the accuracy of the result at as low computational efforts as feasible. The selected optimal strategy is expected to be used in the future simulations of large networks of inter-granular stress corrosion cracks at the grain-size scale using incomplete random tessellation.(author)

  4. Structural, elastic and electronic properties of GaSe under biaxial and uniaxial compressive stress

    Science.gov (United States)

    Kosobutsky, A. V.; Sarkisov, S. Yu.; Brudnyi, V. N.

    2013-09-01

    The influence of anisotropic mechanical stresses preserving symmetry of the hexagonal lattice on the structural, elastic and electronic properties of layered GaSe crystal is studied from first principles. In this work we consider the biaxial compressive stress in the layer planes of GaSe and uniaxial compressive stress applied in the perpendicular direction (along the c axis). The deformation mechanism of GaSe is analyzed in terms of the calculated atomic displacements under load. The changes in the a and c lattice parameters are found to be basically determined by changes in the Ga-Ga-Se bond angle and interlayer distance. According to the obtained stress dependences of the interband transition energies, the band gap continuously decreases with increasing uniaxial pressure, while application of a biaxial load leads to the opposite effect. Calculations of the charge neutrality level (CNL) show that CNL is located in the lower part of the band gap in all the considered cases. Therefore, the dominant p-type conductivity of undoped GaSe crystals can be explained by Fermi level pinning in the lower part of the forbidden band near CNL as a consequence of material defectiveness.

  5. A new analytical method for stress intensity factors based on insitu measurement of crack deformation under biaxial tension

    International Nuclear Information System (INIS)

    A new approach for the calculation of stress intensity factors (SIF) for isotropic and orthotropic materials under biaxial tension loading was proposed in this paper. In order to determine SIF from the full-field displacement data, an asymptotic expansion of the crack tip displacement field was performed. The deforming shape and surface residual stress of the crack tip was obtained at the early extended stage of the loading process by using optical microscope and X-ray diffraction measurement. During this stage, a modified Dugdale Model, which takes into account the coupled effect at the crack tip, was proposed for the open displacement of the crack tip. In this paper, the SIFs of two types of silicon steel sheet with isotropic and orthotropic properties were calculated using the modified Dugdale Model based on the biaxial tension experimental data. From the results, it was found that analysis using the modified Dugdale Model is an effective way to evaluate SIF under biaxial stress.

  6. Biaxial residual stress states of plasma-sprayed hydroxyapatite coatings on titanium alloy substrate.

    Science.gov (United States)

    Yang, Y C; Chan, E; Hwang, B H; Lee, S Y

    2000-07-01

    Biaxial residual stress states of plasma-sprayed hydroxyapatite coatings (HACs) on titanium alloy substrate as a function of plasma power, powder feed rate and coating thickness were studied by X-ray 'sin2 psi' method. The Young's modulus of hydroxyapatite (HA), required for the stress analysis, was measured from the separated free coating by three-point bending test method. It was found that the directions of principal stresses were in proximity to and perpendicular to the spraying direction. The measured Young's moduli of HACs were much lower than the theoretical value reported. The denser, well-melted HAC exhibited a higher residual stress, as compared with the less dense, poor-melting HAC. The denser coatings could be effected by higher plasma power and lower powder feed rate. Significantly, the thicker 200 microm HAC exhibited higher residual stress than that of the thinner 50 microm HAC. The implications of residual stress in HAC for biomaterials are discussed in detail. PMID:10850926

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

    Energy Technology Data Exchange (ETDEWEB)

    Sablik, M.J.; Kwun, H.; Rollwitz, W.L.; Cadena, D.

    1992-01-01

    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.

  8. 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

  9. Measurement of Anisotropic Biaxial Stresses in Si1-xGex/Si Mesa Structures by Oil-Immersion Raman Spectroscopy

    Science.gov (United States)

    Kosemura, Daisuke; Tomita, Motohiro; Usuda, Koji; Tezuka, Tsutomu; Ogura, Atsushi

    2013-04-01

    Anisotropic biaxial stress states in Si1-xGex/Si mesa structures were evaluated by oil-immersion Raman spectroscopy. Using a high-numerical-aperture lens, the electrical field component perpendicular to the surface, i.e., z-polarization, can be obtained. The z-polarization enables the excitation of the forbidden optical phonon mode, i.e., the transverse optical (TO) phonon mode, even under the backscattering geometry from (001)-oriented diamond-type crystals. The anisotropic biaxial stress evaluation of Si1-xGex was considered difficult compared with that of Si, because many unknown parameters exist for Si1-xGex, e.g., phonon deformation potentials (PDPs), the Ge concentration x, and the factor of Raman shift on x. In this study, PDPs and the Ge concentration in Si1-xGex were investigated in detail. As a result, using precise PDPs and x, a clear dependence of anisotropic biaxial stress states in Si1-xGex on the mesa structure shape was observed.

  10. Influence of irradiation, load history, and stress bi-axiality on initiation and propagation of stress corrosion cracks induced by iodine in zirconium alloys

    International Nuclear Information System (INIS)

    The authors present a research study aimed at the modelling of iodine-induced stress corrosion cracking of zirconium alloys. The aim is to develop a damage model coupled with the material mechanical behaviour, and which takes irradiation effects, load history and stress bi-axiality into account. The study comprises iodine-induced stress corrosion cracking tests of a non irradiated material and of a proton-irradiated material, a study of the mechanical behaviour and of the stress corrosion cracking behaviour of the irradiated material, and then the numerical modelling

  11. 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.

  12. Fatigue crack growth under biaxial loading

    Science.gov (United States)

    Lam, Y. C.

    1993-04-01

    Fatigue crack growth under biaxial loading for long cracks subjected to low cyclic stress levels was investigated. The biaxial stress ratio lambda ranging from -0.5 to +1.0 was considered. The strain energy density factor range was used as the criterion for predicting the crack growth rates and crack path. The agreement between prediction and experimental results was reasonable for crack growth rates and marginal for crack paths. The investigation highlighted the inherent difficulties for crack path prediction and indicated the increased sensitivity to initial crack angle and biaxial stress ratio when the biaxial stress ratio approaches unity.

  13. 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.

  14. Effect of biaxial stress on single particle states and binding energies of charged excitons and biexciton in In(Ga)As/GaAs(001) self-assembled quantum dots

    International Nuclear Information System (INIS)

    We study the effect of an external biaxial stress on single particle states and binding energies of charged excitons and biexciton relative to that of neutral exciton in In(Ga)As/GaAs(001) quantum dots. We performed million-atom empirical pseudopotential calculations on realistic In(Ga)As/GaAs(001) quantum dots. We find that compressive biaxial stress increases the electron localization and hole delocalization. The binding energies of the positive trion and biexciton increase under compressive stress. Depending upon the value of binding energy of biexciton and available biaxial stress, the binding energy of biexciton can be tuned to zero which allows for the generation of entangled photon pairs across generations in biexciton cascade process in In(Ga)As/GaAs(001) self-assembled quantum dots.

  15. Influence of biaxial stress on the magnetic properties of cobalt nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Saranu, Srinivasa; Herr, Ulrich [Institut fuer Mikro- und Nanomaterialien, Universitaet Ulm, 89081 Ulm (Germany); Wiedwald, Ulf; Ziemann, Paul [Institut fuer Festkoerperphysik, Universitaet Ulm, 89069 Ulm (Germany)

    2008-07-01

    Co nanoparticles with an average diameter of 25 nm have been produced using an inert gas condensation technique. The particles were deposited on Si substrates and covered in situ with a 20 nm Cu film. When the substrate coverage exceeds 5 %, the remanent magnetization along the in-plane direction was larger than that along the out-of-plane direction which is attributed to the dipolar interaction between the particles. For Co particles on Ta substrates, the effect of stress on the magnetic properties of isolated particles was studied. A thin film of phospholipids (DOPC) on the Ta substrate was used to avoid the agglomeration of the particles during deposition. The lipid layer was removed in an oxygen plasma, afterwards the particles were reduced to metallic Co again using a hydrogen plasma and subsequently covered with 20nm of SiO{sub x}. The effect of stress on the magnetic properties of these particles was studied by loading the Ta substrate with hydrogen. For 0.6% of strain in the Ta substrate, out-of-plane magnetization measurements showed an increase of the saturation field H{sub s} and a reduction of the remanent magnetization. This indicates that 25 nm cobalt nanoparticles have a positive magnetostriction.

  16. NESC VII European project: demonstration of warm pre-stressing effect in biaxial loading conditions - Bending tests on 18MND5 cruciform specimens

    International Nuclear Information System (INIS)

    In the framework of NESC VII European project, a large experimental program has been dedicated to demonstrate the Warm Pre Stressing (WPS) effect in different testing configurations. One of the CEA (France) contributions to this project is the realization of five point bending tests on large cruciform specimens considering different WPS loading cycles. The five cruciform specimens, sponsored by EDF (France) and IRSN (France), are made of 18MND5 steel. Two of them have been tested on a same LCF (Load-Cool-Fracture) loading cycle, including an isothermal pre-loading at T-WPS = -30 degrees C followed by a cooling down to T-FRAC = -150 degrees C at a constant load before an isothermal reloading up to fracture at T-FRAC. The results presented in this paper give a successful demonstration of the Warm Pre Stressing effect in biaxial loading conditions on a LCF cycle. (authors)

  17. Engineering piezoresistivity using biaxially strained silicon

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Richter, Jacob

    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 to enhance the performance of ezoresistive stress sensors.

  18. Application of magnetomechanical hysteresis modeling to magnetic techniques for monitoring neutron embrittlement and biaxial stress. Progress report, June 1991--December 1991

    Energy Technology Data Exchange (ETDEWEB)

    Sablik, M.J.; Kwun, H.; Rollwitz, W.L.; Cadena, D.

    1992-01-01

    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.

  19. NESC VII European project: demonstration of warm pre-stressing effect in biaxial loading conditions - Bending tests on 18MND5 cruciform specimens and their interpretation

    International Nuclear Information System (INIS)

    In the framework of the NESC VII European project, a large experimental program has been dedicated to characterize the Warm Pre-Stressing (WPS) effect in different testing configurations. One of the CEA (France) contributions to this project is the realization of five point bending tests on large cruciform specimens considering different WPS loading cycles. The five cruciform specimens, sponsored by EDF (France) and IRSN (France), are made of 18MND5 steel. Two of them have been tested on a same LCF (Load-Cool-Fracture) loading cycle and two others on the same LCTF (Load-Cool-Transient-Fracture) loading cycle. The experimental results presented in this paper give a successful demonstration of the WPS effect in biaxial loading conditions either on a LCF or on a LCTF cycle. During the test interpretations, different models have then been tested and compared in order to evaluate their ability to predict the cleavage fracture in the case of different WPS loading cycles. They all provide very conservative predictions whatever loading cycle is concerned. (authors)

  20. Biaxial media revisited

    International Nuclear Information System (INIS)

    A detailed review of the properties of optically anisotropic materials (both uniaxial and biaxial) is presented. Attention is particularly focused on the biaxial case, and some little-known features of these media are highlighted. Since the optic axes can be defined in two different ways, there are strictly speaking four optic axes in a biaxial medium rather than just two. And whereas an optic axis is normally defined as a direction in which double refraction (birefringence) does not occur, this statement is certainly incorrect for two of the four optic axes, and arguably incorrect for the other two as well. Interesting ‘avoided crossing’ behaviour of the index surfaces is also demonstrated. The paper provides a valuable resource for anyone preparing a course on the optical properties of crystals or involved in the design of optical systems incorporating biaxial media. (paper)

  1. BIAXIAL LOADING DEVICE FOR DYNAMIC CONCRETE RESPONSE

    OpenAIRE

    Weerheijm, J.; Reinhardt, H.

    1988-01-01

    At the Delft University of Technology the dynamic material response of concrete is being investigated, using the Split Hopkinson Bar technique (SHB). To gain more insight into the influence of initial stress conditions on the dynamic response, the SHB has been combined with a static compression loading device perpendicular to the SHB. The paper describes the test set-up, the monitoring techniques and the tests performed during the development of the biaxial loading device.

  2. Biaxial cyclic deformation behaviour of steels

    International Nuclear Information System (INIS)

    The cyclic stress-strain curves for 1% Cr-Mo-V steel and AISI 316 stainless steel were determined under biaxial loading conditions at various temperatures and strain rates. It is shown that these curves may be correlated in terms of the maximum shear stress and strain amplitudes. It is argued that, even though metals obey the von Mises yield criterion for monotonic leading, the micromechanisms of slip which produce the stabilized cyclic stress-strain behaviour are governed by the Tresca criterion. (author)

  3. Biaxial fracture test of silicon wafers

    Energy Technology Data Exchange (ETDEWEB)

    Funke, C.; Moeller, H.J. [Institut fuer Experimentelle Physik, TU-Bergakademie Freiberg, Silbermannstrasse 1, 09599 Freiberg (Germany); Kullig, E.; Kuna, M. [Institut fuer Mechanik und Fluiddynamik, TU-Bergakademie Freiberg, Lampadiusstr. 4, 09599 Freiberg (Germany)

    2004-07-01

    The statistical fracture stress distribution of silicon wafers was obtained by biaxial plate bending tests in combination with finite element calculations. For the correct interpretation of these tests it is important that the finite element calculations imply wafer thickness and elastic properties of the multicrystalline silicon wafer, otherwise the resulting stresses will be estimated to high. The Weibull distribution of fracture stresses yields different parameters for each test series of silicon, depending on the surface preparation and wafer manufacturing condition. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  4. Structures having enhanced biaxial texture

    Science.gov (United States)

    Goyal, Amit (Knoxville, TN); Budai, John D. (Oak Ridge, TN); Kroeger, Donald M. (Knoxville, TN); Norton, David P. (Knoxville, TN); Specht, Eliot D. (Knoxville, TN); Christen, David K. (Oak Ridge, TN)

    1999-01-01

    A biaxially textured alloy article includes a rolled and annealed biaxially textured base metal substrate characterized by an x-ray diffraction phi scan peak of no more than 20.degree. FWHM; and a biaxially textured layer of an alloy or another material on a surface thereof. The article further includes at least one of an electromagnetic device or an electro-optical device epitaxially joined to the alloy.

  5. Miniature biaxial strain transducer

    Science.gov (United States)

    Hoffman, I. S. (inventor)

    1976-01-01

    A reusable miniature strain transducer for use in the measurement of static or quasi-static, high level, biaxial strain on the surface of test specimens or structures was studied. Two cantilever arms, constructed by machining the material to appropriate flexibility, are self-aligning and constitute the transducing elements of the device. Used in conjunction with strain gages, the device enables testing beyond normal gage limits for high strains and number of load cycles. The device does not require conversion computations since the electrical output of the strain gages is directly proportional to the strain measured.

  6. Exciton dynamics in 121 angstrom GaAs and GaAsP QWs having different valence band structures arising from built-in biaxial stress

    International Nuclear Information System (INIS)

    Exciton dynamics in various 121 angstrom single quantum wells (QWs): a AlGaAs/GaAs QW and two AlGaAs/GaAsP QWs, under different built-in biaxial tension, has been investigated using time resolved photoluminescence (PL) spectroscopy at 5 K. Heavy-hole (hh) and light-hole (lh) exciton formation times from free electron-hole pair, hh (lh) exciton to lh (hh) exciton inter-subband relaxation times, exciton localization times to interface islands, and localized exciton annihilation decay times in the strained and nonstrained QWs have been determined by fitting the PL time profiles at the lowest emission energy with an analytical solution for the localized exciton population profile obtained by solving six level rate equations

  7. Analysis and experimental validation of through-thickness cracked large-scale biaxial fracture tests

    International Nuclear Information System (INIS)

    Since 1984 TWI has been involved in an extensive series of tests investigating the effects of biaxial loading on the fracture behaviour of A533B steel. Testing conditions have ranged from the lower to upper shelf regions of the transition curve and covered a range of biaxiality ratios. In an attempt to elucidate the trends underlying the experimental results, finite element-based mechanistic models were used to analyse the effects of biaxial loading. For ductile fracture, a modified Gunson model was used and important effects on tearing behaviour were found for through thickness cracked wide plates, as observed in upper shelf tests. For cleavage fracture, both simple T-stress methods and the Anderson-Dodds and Beremin models were used. Whilst the effect of biaxiality on surface cracked plates was small, a marked effect of biaxial loading was found for the through-thickness crack. To further validate the numerical predictions for cleavage fracture, TWI have performed an additional series of lower shelf through thickness cracked biaxial wide plate fracture tests. These tests were performed using various biaxiality loading conditions varying from simple uniaxial loading, through equibiaxial loading, to a biaxiality ratio equivalent to a circumferential crack in a pressure vessel. These tests confirmed the predictions that there is a significant effect of biaxial loading on cleavage fracture of through thickness cracked plate. (orig.)

  8. 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.

  9. Biaxial failure surfaces of 2020 and PGX graphites

    International Nuclear Information System (INIS)

    Graphite shows an increase in strength with an increase in temperature, and this characteristic makes graphite a prime candidate for structural applications in the high temperature gas-cooled reactors (HTGR). The core support structure in the HTGR uses high strength graphite. Its ultimate strength under a combined stress state is important for design use. A test program was therefore initiated to determine the multiaxial behavior of two specific types of graphites, in particular the biaxial failure surface which is to be correlated with various failure theories. The two candidate graphites are a fine-grain 2020 (of Stackpole Carbon Company) and a coarse-grain PGX (of Union Carbide Corp). Tubular specimens are used and are subjected axial loading and internal or external pressure. Various ratios of biaxial stresses are examined but emphasis is placed in the first and fourth stress quadrants. The tensile fracture pattern reveals a cleavage failure mode. Compressive failure occurs when a limiting value (equivalent to cohesion and internal friction) on any given plane is reached. The maximum stresses at the time of failure are calculated using the thick-wall cylinder formula. A modified Coulomb-Mohr theory with tension-cutoffs proposed by B. Paul (1961) fits the biaxial test data very well. The theory is consistent with the observed fracture patterns and mechanism. The theory appears to give a better correlation with the biaxial test data than the maximum normal stress, mest data than the maximum normal stress, maximum shear stress, maximum distortion energy and Tsai and Wu's strength tensor theories. The failure surfaces obtained are for thin tubular specimen configuration in which the stress state is relatively uniform. The volume and grain size effects are nearly the same. In the application of the failure surfaces to the core support component design, these factors, non-uniform stress state, the volume and grain size effects should be included. (orig.)

  10. Biaxial mechanical characterization of bat wing skin.

    Science.gov (United States)

    Skulborstad, A J; Swartz, S M; Goulbourne, N C

    2015-01-01

    The highly flexible and stretchable wing skin of bats, together with the skeletal structure and musculature, enables large changes in wing shape during flight. Such compliance distinguishes bat wings from those of all other flying animals. Although several studies have investigated the aerodynamics and kinematics of bats, few have examined the complex histology and mechanical response of the wing skin. This work presents the first biaxial characterization of the local deformation, mechanical properties, and fiber kinematics of bat wing skin. Analysis of these data has provided insight into the relationships among the structural morphology, mechanical properties, and functionality of wing skin. Large spatial variations in tissue deformation and non-negligible fiber strains in the cross-fiber direction for both chordwise and spanwise fibers indicate fibers should be modeled as two-dimensional elements. The macroscopic constitutive behavior was anisotropic and nonlinear, with very low spanwise and chordwise stiffness (hundreds of kilopascals) in the toe region of the stress-strain curve. The structural arrangement of the fibers and matrix facilitates a low energy mechanism for wing deployment and extension, and we fabricate examples of skins capturing this mechanism. We propose a comprehensive deformation map for the entire loading regime. The results of this work underscore the importance of biaxial field approaches for soft heterogeneous tissue, and provide a foundation for development of bio-inspired skins to probe the effects of the wing skin properties on aerodynamic performance. PMID:25895436

  11. Biaxial low-cycle fatigue failure of 316 stainless steel at elevated temperatures

    International Nuclear Information System (INIS)

    High-strain, biaxial fatigue tests between the limiting conditions of uniaxial push-pull and fully reversed pure torsional loading were repeated on two batches of AISI 316 stainless steel, one tested at 4000C, the other at 5500C. An equivalent plastic shear strain range was shown to be superior to the octahedral equivalent strain for correlating biaxial fatigue endurance data. The stable cyclic stress-strain behaviour for any biaxial state is best represented in terms of the maximum shear stress and shear strain. At 5500C dynamic strain aging has a significant effect on both plastic flow and endurance for certain strain rates. Both Stage I and Stage II cracks were identified in the biaxial tests. (author)

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

    OpenAIRE

    Gaur Vidit; Mbiakop-Ngassa Armel-Brice; Doquet Véronique; Roguet Eléonore; Persent Emmanuel

    2014-01-01

    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 a...

  13. 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)

  14. Biaxial mechanical properties of swine uterosacral and cardinal ligaments.

    Science.gov (United States)

    Becker, Winston R; De Vita, Raffaella

    2014-09-14

    Mechanical alterations to pelvic floor ligaments may contribute to the development and progression of pelvic floor disorders. In this study, the first biaxial elastic and viscoelastic properties were determined for uterosacral ligament (USL) and cardinal ligament (CL) complexes harvested from adult female swine. Biaxial stress-stretch data revealed that the ligaments undergo large strains. They are orthotropic, being typically stiffer along their main physiological loading direction (i.e., normal to the upper vaginal wall). Biaxial stress relaxation data showed that the ligaments relax equally in both loading directions and more when they are less stretched. In order to describe the experimental findings, a three-dimensional constitutive law based on the Pipkin-Rogers integral series was formulated. The model accounts for incompressibility, large deformations, nonlinear elasticity, orthotropy, and stretch-dependent stress relaxation. This combined theoretical and experimental study provides new knowledge about the mechanical properties of USLs and CLs that could lead to the development of new preventive and treatment methods for pelvic floor disorders. PMID:25218641

  15. Plastic behaviour and forming limit during biaxial compressions of magnesium alloy AZ31 at room temperature

    Directory of Open Access Journals (Sweden)

    Shimizu I.

    2010-06-01

    Full Text Available The plastic behaviour and compressive fracture of AZ31 magnesium alloy were examined at room temperature. The uniaxial compression tests and biaxial compression tests along linear and nonlinear strain paths were carried out until fracture using a unique biaxial compression testing machine developed by author. The results revealed the evolution of plastic anisotropy in biaxial compressions, that is the strain path dependency of work hardening. The adaptability of several forming limit criteria to the compressive fracture of AZ31 alloy was discussed. It was found that the uniform estimation of compressive forming limits by uniaxial and biaxial compressions was difficult by Freudenthal criterion and Oyane criterion. The result of Tresca energy criterion suggested that the criterion based on shear stress has possibility to predict the compressive forming limits at room temperature of AZ31 alloy.

  16. Plastic behaviour and forming limit during biaxial compressions of magnesium alloy AZ31 at room temperature

    Science.gov (United States)

    Shimizu, I.; Tada, N.

    2010-06-01

    The plastic behaviour and compressive fracture of AZ31 magnesium alloy were examined at room temperature. The uniaxial compression tests and biaxial compression tests along linear and nonlinear strain paths were carried out until fracture using a unique biaxial compression testing machine developed by author. The results revealed the evolution of plastic anisotropy in biaxial compressions, that is the strain path dependency of work hardening. The adaptability of several forming limit criteria to the compressive fracture of AZ31 alloy was discussed. It was found that the uniform estimation of compressive forming limits by uniaxial and biaxial compressions was difficult by Freudenthal criterion and Oyane criterion. The result of Tresca energy criterion suggested that the criterion based on shear stress has possibility to predict the compressive forming limits at room temperature of AZ31 alloy.

  17. 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.

  18. In situ characterization of martensite variant formation in nickel-titanium shape memory alloy under biaxial loading

    International Nuclear Information System (INIS)

    Martensite morphology in a NiTi alloy under uni- and biaxial loading was studied in situ using high-resolution microscopy, electron backscatter diffraction and local strain analyses. The results obtained clearly indicate that a different martensite morphology, including a higher number of martensite variants, evolved in NiTi under biaxial stress states. However, the phase transformation was still triggered by shear stresses, eventually affecting deformation and fatigue-related phenomena.

  19. Biaxially textured articles formed by plastic deformation

    Science.gov (United States)

    Goyal, Amit (Knoxville, TN)

    2001-01-01

    A method of preparing a biaxially textured article comprises the steps of providing a metal preform, coating or laminating the preform with a metal layer, deforming the layer to a sufficient degree, and rapidly recrystallizing the layer to produce a biaxial texture. A superconducting epitaxial layer may then be deposited on the biaxial texture. In some embodiments the article further comprises buffer layers, electromagnetic devices or electro-optical devices.

  20. Rolling process for producing biaxially textured substrates

    Science.gov (United States)

    Goyal, Amit

    2004-05-25

    A method of preparing a biaxially textured article includes the steps of: rolling a metal preform while applying shear force thereto to form as-rolled biaxially textured substrate having an a rotated cube texture wherein a (100) cube face thereof is parallel to a surface of said substrate, and wherein a [100] direction thereof is at an angle of at least 30.degree. relative to the rolling direction; and depositing onto the surface of the biaxially textured substrate at least one epitaxial layer of another material to form a biaxially textured article.

  1. 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

  2. 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.

  3. Buffer layers on biaxially textured metal substrates

    Science.gov (United States)

    Shoup, Shara S. (Woodstock, GA); Paranthamam, Mariappan (Knoxville, TN); Beach, David B. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Goyal, Amit (Knoxville, TN)

    2001-01-01

    A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.

  4. 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

  5. A proposal of parameter to predict biaxial fatigue life for CF8M cast stainless steels

    International Nuclear Information System (INIS)

    Biaxial low cycle fatigue test was carried out to predict fatigue life under combined axial-torsional loading condition which is that of in-phase and out-of-phase for CF8M cast stainless steels. Fatemi Socie(FS) parameter which is based on critical plane approach is not only one of methods but also the best method that can predict fatigue life under biaxial loading condition. But the result showed that, biaxial fatigue life prediction by using FS parameter with several different parameters for the CF8M cast stainless steels is not conservative but best results. So in this present research, we proposed new fatigue life prediction parameter considering effective shear stress instead of FS parameter which considers the maximum normal stress acting on maximum shear strain and its effectiveness was verified

  6. Shape recovery characteristics of biaxially prestrained Fe-Mn-Si-based shape memory alloy

    International Nuclear Information System (INIS)

    Fe-Mn-Si-based shape memory alloy has already been used practically for steel pipe joints. In most of the applications including the steel pipe joints, it is possible to estimate the reduction of diameter from the experimental data of the shape recovery after uniaxial stretching of the alloy materials. However, studies on shape recovery effects after biaxial stretching are important for the extensive applications of the alloy. In this study, we investigated the shape recovery strain after uniaxial and biaxial stretching and the microstructures of the alloy in order to see the effects of uniaxial and biaxial prestrain on the stress-induced martensitic transformation. Amounts of shape recovery strain in the biaxially prestrained specimens are smaller than those in the uniaxially prestrained specimens. Transmission electron microscopy revealed that reverse transformations of stress-induced martensitic ?-phase are prevented by slip bands formed at the same time in the biaxially prestrained specimens, but not in the uniaxially prestrained specimens. The technological data and interpretations presented in this study should be useful in forming design guidelines for promoting the extensive applications of Fe-Mn-Si-based shape memory alloy

  7. Biaxial low cycle fatigue behavior and martensite formation of a metastable austenitic cast TRIP steel under proportional Loading

    Energy Technology Data Exchange (ETDEWEB)

    Kulawinski, D.; Ackermann, S.; Glage, A.; Henkel, S.; Biermann, H. [Institute of Materials Engineering, Technische Universitaet Bergakademie Freiberg (Germany)

    2011-09-15

    In this paper the biaxial low cycle fatigue behavior under proportional loading of a recently developed metastable austenitic stainless cast steel is presented. Total strain controlled tests were carried out on a 250 kN biaxial servohydraulic tension-compression testing machine equipped with a biaxial orthogonal extensometer to measure the principal strains in the gauge area of the used cruciform specimens. The principal stresses were determined based on the compliance after the load reversals. The low cycle fatigue behavior under biaxial synchronous loading is compared to the uniaxial behavior. Therefore, biaxial single step tests and a biaxial multiple step load increase test were carried out. The dependence of the stress state on the cyclic deformation curves, cyclic stress-strain curves and the formation of martensite are described. Finally, the fatigue life relationship according to Basquin and Manson-Coffin was determined and compared to the Smith, Watson and Topper damage parameter, which provides a satisfactory fatigue life prediction. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Crack under biaxial loading: Two-parameter description and prediction of crack growth direction.

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav

    2014-01-01

    Ro?. 31, APR (2014), s. 44-49. ISSN 0213-3725 R&D Projects: GA MŠk(CZ) 7AMB14AT012 Institutional support: RVO:68081723 Keywords : Concrete * T-stress * cracks growth prediction * numerical calculation * biaxial loading Subject RIV: JL - Materials Fatigue, Friction Mechanics

  9. Periodic structures in a biaxial nematic phase

    Science.gov (United States)

    Palangana, A. J.; Simões, M.; Dos Santos, O. R.; Alves, F. S.

    2003-03-01

    In this work experimental and theoretical results will be used to show that under convenient conditions; appropriated geometry, well chosen boundary conditions, and suitable external fields, the elastic and dynamic behavior of a sample of a biaxial nematic liquid crystal can become similar to the one observed on usual uniaxial nematic liquid crystals. It is shown that this result can be used to determine the values of some combinations of the rheologic parameters of the biaxial phase.

  10. Biaxial mechanical modeling of the small intestine.

    Science.gov (United States)

    Bellini, Chiara; Glass, Paul; Sitti, Metin; Di Martino, Elena S

    2011-11-01

    Capsule endoscopes are pill-size devices provided with a camera that capture images of the small intestine from inside the body after being ingested by a patient. The interaction between intestinal tissue and capsule endoscopes needs to be investigated to optimize capsule design while preventing tissue damage. To that purpose, a constitutive model that can reliably predict the mechanical response of the intestinal tissue under complex mechanical loading is required. This paper describes the development and numerical validation of a phenomenological constitutive model for the porcine duodenum, jejunum and ileum. Parameters characterizing the mechanical behavior of the material were estimated from planar biaxial test data, where intestinal tissue specimens were simultaneously loaded along the circumferential and longitudinal directions. Specimen-specific Fung constitutive models were able to accurately predict the planar stress-strain behavior of the tested samples under a wide range of loading conditions. To increase model generality, average anisotropic constitutive relationships were also generated for each tissue region by fitting average stress-strain curves to the Fung potential. Due to the observed variability in the direction of maximum stiffness, the average Fung models were less anisotropic than the specimen-specific models. Hence, average isotropic models in the Neo-Hookean and Mooney-Rivlin forms were attempted, but they could not adequately describe the degree of nonlinearity in the tissue. Values of the R2 for the nonlinear regressions were 0.17, 0.44 and 0.93 for the average Neo-Hookean, Mooney-Rivlin and Fung models, respectively. Average models were successfully implemented into FORTRAN routines and used to simulate capsule deployment with a finite element method analysis. PMID:22098873

  11. Evaluating the time and temperature dependent biaxial strength of Gore-Select {sup registered} series 57 proton exchange membrane using a pressure loaded blister test

    Energy Technology Data Exchange (ETDEWEB)

    Grohs, Jacob R.; Dillard, David A.; Case, Scott W. [Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0219 (United States); Li, Yongqiang; Lai, Yeh-Hung; Gittleman, Craig S. [Electrochemical Energy Research Lab, GM R and D, General Motors Corporation, 10 Carriage Street, Honeoye Falls, NY 14472-0603 (United States); Ellis, Michael W. [Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0238 (United States)

    2010-01-15

    Temperature and humidity fluctuations in operating fuel cells impose significant biaxial stresses in the constrained proton exchange membranes (PEMs) of a fuel cell stack. The strength of the PEM, and its ability to withstand cyclic environment-induced stresses, plays an important role in membrane integrity and consequently, fuel cell durability. In this study, a pressure loaded blister test is used to characterize the biaxial strength of Gore-Select {sup registered} series 57 over a range of times and temperatures. Hencky's classical solution for a pressurized circular membrane is used to estimate biaxial strength values from burst pressure measurements. A hereditary integral is employed to construct the linear viscoelastic analog to Hencky's linear elastic exact solution. Biaxial strength master curves are constructed using traditional time-temperature superposition principle techniques and the associated temperature shift factors show good agreement with shift factors obtained from constitutive (stress relaxation) and fracture (knife slit) tests of the material. (author)

  12. Biaxial Fatigue Crack Growth Behavior in Aluminum Alloy 5083-H116 Under Ambient Laboratory and Saltwater Environments

    Science.gov (United States)

    Perel, V. Y.; Misak, H. E.; Mall, S.; Jain, V. K.

    2015-02-01

    Crack growth of aluminum alloy 5083 was investigated when subjected to the in-plane biaxial tension-tension fatigue with stress ratio of 0.5 under ambient laboratory and saltwater environments. Cruciform specimens with a center hole, containing a notch and precrack at 45° to the specimen's arms, were tested in a biaxial fatigue test machine. Two biaxiality ratios, ? = 1 and ? = 1.5, were studied. For ? = 1, crack propagated along a straight line collinearly with the precrack, while for ? = 1.5 case, the crack path was curved and non-collinear with the precrack. Uniaxial fatigue tests were also conducted. Crack growth rates were faster under the biaxiality fatigue in comparison to uniaxial fatigue at a given crack driving force (?K I or ?G) in both environments. Further, an increase in biaxiality ratio increased the crack growth rate, i.e., faster for ? = 1.5 case than ? = 1 case. Both biaxial fatigue and saltwater environment showed detrimental effects on the fatigue crack growth resistance of 5083, and its combination is highly detrimental when compared to uniaxial fatigue.

  13. Biaxial Fatigue Crack Growth Behavior in Aluminum Alloy 5083-H116 Under Ambient Laboratory and Saltwater Environments

    Science.gov (United States)

    Perel, V. Y.; Misak, H. E.; Mall, S.; Jain, V. K.

    2015-04-01

    Crack growth of aluminum alloy 5083 was investigated when subjected to the in-plane biaxial tension-tension fatigue with stress ratio of 0.5 under ambient laboratory and saltwater environments. Cruciform specimens with a center hole, containing a notch and precrack at 45° to the specimen's arms, were tested in a biaxial fatigue test machine. Two biaxiality ratios, ? = 1 and ? = 1.5, were studied. For ? = 1, crack propagated along a straight line collinearly with the precrack, while for ? = 1.5 case, the crack path was curved and non-collinear with the precrack. Uniaxial fatigue tests were also conducted. Crack growth rates were faster under the biaxiality fatigue in comparison to uniaxial fatigue at a given crack driving force (? K I or ? G) in both environments. Further, an increase in biaxiality ratio increased the crack growth rate, i.e., faster for ? = 1.5 case than ? = 1 case. Both biaxial fatigue and saltwater environment showed detrimental effects on the fatigue crack growth resistance of 5083, and its combination is highly detrimental when compared to uniaxial fatigue.

  14. Electrodeposition of biaxially textured layers on a substrate

    Science.gov (United States)

    Bhattacharya, Raghu N; Phok, Sovannary; Spagnol, Priscila; Chaudhuri, Tapas

    2013-11-19

    Methods of producing one or more biaxially textured layer on a substrate, and articles produced by the methods, are disclosed. An exemplary method may comprise electrodepositing on the substrate a precursor material selected from the group consisting of rare earths, transition metals, actinide, lanthanides, and oxides thereof. An exemplary article (150) may comprise a biaxially textured base material (130), and at least one biaxially textured layer (110) selected from the group consisting of rare earths, transition metals, actinides, lanthanides, and oxides thereof. The at least one biaxially textured layer (110) is formed by electrodeposition on the biaxially textured base material (130).

  15. Biaxial laser-based displacement transducer

    Science.gov (United States)

    Sharpe, W. N., Jr.; Payne, T. S.; Smith, M. K.

    1978-01-01

    A simple laser-based instrument is described which produces output voltages proportional to displacements in orthogonal directions. This instrument and the associated experimental techniques have been used to measure biaxial displacements across 400-micron slots at various angles in sheet specimens of various widths.

  16. 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.

  17. Miniature load cell instrumentation for finite deformation biaxial testing of elastomers

    Science.gov (United States)

    Arenz, R. J.; Landel, R. F.; Tsuge, K.

    1974-01-01

    Accuracy of biaxial test equipment to examine the nonlinear mechanical behavior of thin sheet specimens of elastomeric materials has been hampered by lack of precise determination of the force distribution along the sides of the specimen. It has been necessary to use an effective width established by approximate means to obtain the stress from the overall force applied along the edges. To avoid this experimental difficulty, individual miniature proof-ring load cells utilizing semiconductor strain gages have been developed and applied to the support hooks for the thin sheet specimens. Typical results are shown for time-dependent stress distributions for all degrees of biaxiality. An accurate evaluation of the effective specimen width is now possible.

  18. Structural failure of two-density-layer cohesionless biaxial ellipsoids

    CERN Document Server

    Hirabayashi, Masatoshi

    2014-01-01

    This paper quantitatively evaluates structural failure of biaxial cohesionless ellipsoids that have a two-density-layer distribution. The internal density layer is modeled as a sphere, while the external density layer is the rest of the part. The density is supposed to be constant in each layer. The present study derives averaged stresses over the whole volume of these bodies and uses limit analysis to determine their global failure. The upper bound condition of global failure is considered in terms of the size of the internal layer and the aspect ratio of the shape. The result shows that the two-density-layer causes the body to have different strength against structural failure.

  19. Planar biaxial characterization of diseased human coronary and carotid arteries for computational modeling

    OpenAIRE

    Kural, Mehmet H.; Cai, Mingchao; Tang, Dalin; Gwyther, Tracy; Zheng, Jie; Billiar, Kristen L.

    2012-01-01

    Computational models have the potential to provide precise estimates of stresses and strains associated with sites of coronary plaque rupture. However, lack of adequate mathematical description of diseased human vessel wall mechanical properties is hindering computational accuracy. The goal of this study is to characterize the behavior of diseased human coronary and carotid arteries using planar biaxial testing. Diseased coronary specimens exhibit relatively high stiffness (50–210 kPa) and ...

  20. Valence band structure and density of states effective mass model of biaxial tensile strained silicon based on k · p theory

    International Nuclear Information System (INIS)

    After constructing a stress and strain model, the valence bands of in-plane biaxial tensile strained Si is calculated by k · p method. In the paper we calculate the accurate anisotropy valance bands and the splitting energy between light and heavy hole bands. The results show that the valance bands are highly distorted, and the anisotropy is more obvious. To obtain the density of states (DOS) effective mass, which is a very important parameter for device modeling, a DOS effective mass model of biaxial tensile strained Si is constructed based on the valance band calculation. This model can be directly used in the device model of metal—oxide semiconductor field effect transistor (MOSFET). It also a provides valuable reference for biaxial tensile strained silicon MOSFET design. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  1. 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.

  2. Human annulus fibrosus material properties from biaxial testing and constitutive modeling are altered with degeneration.

    Science.gov (United States)

    O'Connell, Grace D; Sen, Sounok; Elliott, Dawn M

    2012-03-01

    The annulus fibrosus (AF) of the intervertebral disk undergoes large and multidirectional stresses and strains. Uniaxial tensile tests are limited for measuring AF material properties, because freely contracting edges can prevent fiber stretch and are not representative of in situ boundary conditions. The objectives of this study were to measure human AF biaxial tensile mechanics and to apply and validate a constitutive model to determine material properties. Biaxial tensile tests were performed on samples oriented along the circumferential-axial and the radial-axial directions. Data were fit to a structurally motivated anisotropic hyperelastic model composed of isotropic extra-fibrillar matrix, nonlinear fibers, and fiber-matrix interactions (FMI) normal to the fibers. The validated model was used to simulate shear and uniaxial tensile behavior, to investigate AF structure-function, and to quantify the effect of degeneration. The biaxial stress-strain response was described well by the model (R (2) > 0.9). The model showed that the parameters for fiber nonlinearity and the normal FMI correlated with degeneration, resulting in an elongated toe-region and lower stiffness with degeneration. The model simulations in shear and uniaxial tension successfully matched previously published circumferential direction Young's modulus, provided an explanation for the low values in previously published axial direction Young's modulus, and was able to simulate shear mechanics. The normal FMI were important contributors to stress and changed with degeneration, therefore, their microstructural and compositional source should be investigated. Finally, the biaxial mechanical data and constitutive model can be incorporated into a disk finite element model to provide improved quantification of disk mechanics. PMID:21748426

  3. Damage and failure behavior of metal matrix composites under biaxial loads

    Science.gov (United States)

    Kirkpatrick, Steven Wayne

    Metal matrix composites (MMCs) are being considered for increased use in structures that require the ductility and damage tolerance of the metal matrix and the enhanced strength and creep resistance at elevated temperatures of high performance fibers. Particularly promising for advanced aerospace engines and airframes are SiC fiber/titanium matrix composites (TMCs). A large program was undertaken in the Air Force to characterize the deformation and failure behaviors of TMCs and to develop computational models that can be used for component design. The effort reported here focused on a SiC SCS-6/Timetal 21S composite under biaxial loading conditions. Biaxial loading conditions are important because multiaxial stresses have been shown to influence the strength and ductility of engineering materials and, in general, structural components are subjected to multiaxial loads. The TMC material response, including stress-strain curves and failure surfaces, was measured using a combination of off-axis uniaxial tension and compression tests and biaxial cruciform tests. The off-axis tests produce combinations of in-plane tension, compression, and shear stresses, the mix of which are controlled by the relative angle between the fiber and specimen axes. The biaxial cruciform tests allowed independent control over the tensile or compressive loads in the fiber and transverse directions. The results of these characterization tests were used to develop a microstructural constitutive model and failure criteria. The basis of the micromechanical constitutive model is a representative unit volume of the MMC with a periodic array of fibers. The representative unit volume is divided into a fiber and three matrix cells for which the microstructural equilibrium and compatibility equations can be analyzed. The resulting constitutive model and associated failure criteria can be used to predict the material behavior under general loading conditions.

  4. Method for making biaxially textured articles by plastic deformation

    Science.gov (United States)

    Goyal, Amit (Knoxville, TN)

    2002-01-01

    A method of preparing a biaxially textured article comprises the steps of providing a metal preform, coating or laminating the preform with a metal layer, deforming the layer to a sufficient degree, and rapidly recrystallizing the layer to produce a biaxial texture. A superconducting epitaxial layer may then be deposited on the biaxial texture. In some embodiments the article further comprises buffer layers, electromagnetic devices or electro-optical devices.

  5. Biaxial unloading and springback behavior of dual-phase DP590 steel using cruciform specimens

    Science.gov (United States)

    Korkolis, Yannis P.; Deng, Nengxiu; Kuwabara, Toshihiko

    2013-12-01

    The unloading behavior of a dual-phase steel (DP590) from a biaxial state of stress was probed using a newly-designed cruciform specimen. The specimen was designed to develop uniform and relatively large plastic strains (over 15% equivalent logarithmic plastic strain) in the gage section, before failure. Nine radial loading paths in the 1st quadrant of the plane stress space were probed. The experiments involved repeated loading and unloading up to failure. At every unloading, the initial response was found to agree with the linear, orthotropically elastic response of the undeformed material. This first linear response was followed by a second one, at a reduced slope. Beyond that, the recorded response was fully non-linear. The same sequence of events was observed during each reloading. The biaxial non-linear strain recovery components ?xnl and ?ynl were measured to be on average approximately 11% of the elastic strains ?xe and ?ye, respectively. This ratio was found to increase with plastic deformation. Subsequently, these biaxial experiments were used to calibrate the Yld2000-2D yield function.

  6. Reference load solutions for plates with semi-elliptical surface cracks subjected to biaxial tensile loading

    International Nuclear Information System (INIS)

    The yield or limit load is a key parameter with respect to the accuracy of flaw assessment based on R6 type procedures such as the R6 routine, the SINTAP and FITNET method, the standard BS 7910 and others. In a number of previous papers two of the present authors proposed the use of a reference load instead of the common limit load, which not only provided more exact fracture mechanics predictions, but showed also a wider and more general application range than the conventional parameter. Here the method has been extended to biaxial tensile loading and it has been successfully validated by a thorough comparison with finite element results and alternative solutions available in the literature. - Highlights: • Reference yield stress solutions are provided for plates with surface flaws. • Tension, bending, combined tension-bending and biaxial loading are considered. • Biaxial loading solutions given in terms of first principal or equivalent stress. • Good approximation of J-integral for different crack sizes and loading conditions. • Less conservatism compared to existing solutions in the literature

  7. An instrument to obtain the correct biaxial hyperelastic parameters of silicones for accurate DEA modelling

    Science.gov (United States)

    Rosset, Samuel; Maffli, Luc; Houis, Simon; Shea, Herbert R.

    2014-03-01

    The analytical formulas describing the behaviour of dielectric elastomer actuators (DEAs) are based on hyperelastic strain energy density functions. The analytical modelling of a DEA will only lead to meaningful results if the dielectric elastomer can be accurately represented by the chosen hyperelastic model and if its parameters are carefully matched to the elastomer. In the case of silicone elastomers, we show that the strain energy density of a thin elastomeric membrane depends on the maximum deformation the membrane was previously submitted to (Mullins effect). We also show that using model parameters coming from an uniaxial pull-test to predict the behaviour of the elastomer in an equi-biaxial configuration leads to erroneous results. We have therefore built a measurement setup, which allows testing thin elastomeric membranes under equi-biaxial stress by inflating them with a pressure source. When modelling a DEA under equi-biaxial stretch, the measurement data can be used directly, without the need of an hyperelastic model, leading to voltage-stretch prediction closer the the measured stress-stretch behaviour of the dielectric membrane.

  8. Biaxial Flexural Strength and Estimation of Size on the Strength Properties of FRP Composites

    Directory of Open Access Journals (Sweden)

    M. N. Saraf

    2013-04-01

    Full Text Available Fibre reinforced plastics (FRP are widely used as structural materials. For designing structural components, a designer is provided with data based on unidirectional testing. But in real structural applications the component is subjected to multiaxial stress throughout the material. Hence a multiaxial test is a better gauge of the behaviour of FRP components in service. In the present paper a ring-on-ring method was adopted which produces biaxial flexural stress on the FRP specimen. Wubull's statistical weakest link theory was applied to standardize the complexity and to assess the reliability of the results.

  9. Results of uniaxial and biaxial tests on riveted fuselage lap joint specimens

    Science.gov (United States)

    Vlieger, H.

    1994-01-01

    As part of an FAA-NLR collaborative program on structural integrity of aging aircraft, NLR carried out uniaxial and biaxial fatigue tests on riveted lap joint specimens being representative for application in a fuselage. All tests were constant amplitude tests with maximum stresses being representative for fuselage pressurization cycles and R-values of 0.1. The parameters selected in the testing program were the stress level (sigma(sub max) = 14 and 16 ksi) and the rivet spacing (0.75 and 1.0 inch). All specimens contained 3 rows of countersunk rivets, the rivet row spacing was 1 inch and the rivet orientation continuous.

  10. Structures having enhanced biaxial texture and method of fabricating same

    Science.gov (United States)

    Goyal, A.; Budai, J.D.; Kroeger, D.M.; Norton, D.P.; Specht, E.D.; Christen, D.K.

    1999-04-27

    A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs.

  11. Biaxially textured articles formed by powder metallurgy

    Science.gov (United States)

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

    2005-05-10

    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.

  12. 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.

  13. Experimental studies of yield phenomena in biaxially loaded metals

    International Nuclear Information System (INIS)

    Realistic materials properties input represents one of the major limitations in computer stress analysis in the plastic range. Lack of data on the response of many structural materials to multiaxial loading requires modeling plastic behavior. Such models can at best predict the response of a limited class of materials for a limited range of loading. A summary of biaxial plasticity experiments on metals is presented to provide a testing ground for such models and to serve as a reference guide for materials that may be of practical interest. Most of the work has been done on materials assumed to exhibit time-and-pressure-independent plastic flow. Special attention is focused on initial and subsequent yield conditions and stress-strain relations. Some specific examples of material behavior that does not fall within the assumptions of classical plasticity theories are discussed. These include time-dependence as evidenced in creep, cyclic loading and strain-rate effects, pressure dependence, large strain behavior, microstructural changes and failure laws. 15 figures, 277 references

  14. Experimental studies of yield phenomena in biaxially loaded metals. [Review

    Energy Technology Data Exchange (ETDEWEB)

    Hecker, S.S.

    1976-01-01

    Realistic materials properties input represents one of the major limitations in computer stress analysis in the plastic range. Lack of data on the response of many structural materials to multiaxial loading requires modeling plastic behavior. Such models can at best predict the response of a limited class of materials for a limited range of loading. A summary of biaxial plasticity experiments on metals is presented to provide a testing ground for such models and to serve as a reference guide for materials that may be of practical interest. Most of the work has been done on materials assumed to exhibit time-and-pressure-independent plastic flow. Special attention is focused on initial and subsequent yield conditions and stress-strain relations. Some specific examples of material behavior that does not fall within the assumptions of classical plasticity theories are discussed. These include time-dependence as evidenced in creep, cyclic loading and strain-rate effects, pressure dependence, large strain behavior, microstructural changes and failure laws. 15 figures, 277 references.

  15. Laminate articles on biaxially textured metal substrates

    Science.gov (United States)

    Beach, David B.; Morrell, Jonathan S.; Paranthaman, Mariappan; Chirayil, Thomas; Specht, Eliot D.; Goyal, Amit

    2003-12-16

    A laminate article comprises a substrate and a biaxially textured (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer over the substrate, wherein 0biaxially textured metal, such as nickel. A method of forming the laminate article is also disclosed.

  16. Biaxial mechanical tests in zircaloy-4

    International Nuclear Information System (INIS)

    The texture of the zircaloy-4 tubes used as cladding in nuclear fuel elements determines anisotropy of the mechanical properties. As a consequence, the uniaxial tests to determine the mechanical behaviour of the tubes are incomplete. Furthermore, the cladding in use is subject to creep with a state of biaxial tensions. For this reason it is also important to determine the biaxial mechanical properties. The creep tests were performed by internal pressure for a state of axial to circumferential tensions of 0.5. Among the experimental procedures are described: preparation of the test specimens, pressurizing equipment, and the implementation of a device that permits a permanent register of the deformation. For the non-irradiated Atucha type zircaloy-4 sheaths, experimental curves of circumferential deformation versus time were obtained, in tests at constant pressure and for different values of temperature and pressure. An empirical function was determined to adjust the experimental values for the speed of the circumferential deformation in terms of the initial tension applied, temperature and deformation, and the change of the corresponding parameters in accordance to the range of the tensions. Also the activation energy for creep was determined. (M.E.L.)

  17. Biaxial loading and shallow-flaw effects on crack-tip constraint and fracture toughness

    International Nuclear Information System (INIS)

    A program to develop and evaluate fracture methodologies for the assessment of crack-tip constraint effects on fracture toughness of reactor pressure vessel (RPV) steels has been initiated in the Heavy-Section Steel Technology (HSST) Program. Crack-tip constraint is an issue that significantly impacts fracture mechanics technologies employed in safety assessment procedures for commercially licensed nuclear RPVs. The focus of studies described herein is on the evaluation of two stressed-based methodologies for quantifying crack-tip constraint (i.e., J-Q theory and a micromechanical scaling model based on critical stressed volumes) through applications to experimental and fractographic data. Data were utilized from single-edge notch bend (SENB) specimens and HSST-developed cruciform beam specimens that were tested in HSST shallow-crack and biaxial testing programs. Results from applications indicate that both the J-Q methodology and the micromechanical scaling model can be used successfully to interpret experimental data from the shallow- and deep-crack SENB specimen tests. When applied to the uniaxially and biaxially loaded cruciform specimens, the two methodologies showed some promising features, but also raised several questions concerning the interpretation of constraint conditions in the specimen based on near-tip stress fields. Fractographic data taken from the fracture surfaces of the SENB and cruciform specimens are used to assess the relevance of stress-based fracture characterizations to conditions at cleavage initiation sites. Unresolved issues identified from these analyses require resolution as part of a validation process for biaxial loading applications. This report is designated as HSST Report No. 142

  18. Biaxial creep testing of textured Ti-3AI-2.5V tubing

    Science.gov (United States)

    Venkatesan, Vasudev; Mahmood, Sheikh T.; Murty, K. Linga

    1990-11-01

    Creep anisotropy of annealed Ti-3A1-2.5V tubing has been studied under biaxial stress conditions at 673 K using internal pressurization combined with axial loading. Biaxial strains were measured in situ during creep using laser and linear variable differential transformer (LVDT) extensometers. Creep data were obtained for different stress ratios (? = ??/gsz @#@), and the steady-state creep rates were found to obey power law with a stress exponent of 4.5 ±0.2 essentially independent of the stress state. Trie experimentally determined creep locus constructed at a constant value of the dissipative work function (W) deviated significantly from isotropy, indicating anisotropy of the material caused by crystallographic texture. The anisotropy parameters (R and P) in the modified Hill’s equation were obtained from the locus fitted to the experimental data to be 5.9 and 1.0, respectively. The crystallographic texture of the material was characterized through inverse and direct pole figures using X-ray diffraction techniques. The crystallite orientation distribution function (CODF) was derived from the pole figure data and represented graphically in the form of Euler plots. This CODF, along with the lower-bound plasticity model, was employed for model predictions of the anisotropy parameters and the creep loci assuming the dominance of basal, prismatic, and pyramidal slip systems. The texture-based predictions differ from the experimental results, and probable reasons for the discrepancy are discussed.

  19. Epitaxial growth of biaxially oriented YBCO films on silver

    International Nuclear Information System (INIS)

    YBCO films were deposited on (100), (110) and (111) oriented silver single crystals and {100} , {110} and {012} biaxially textured Ag substrates by pulsed laser deposition. It is shown that the (100) and (110) orientated single crystals and the {110} biaxially textured Ag tape are all suitable for the deposition of YBCO thin films with c-axis in-plane alignment. The Jc of YBCO film deposited on {110} biaxially textured Ag foil is 7x105A cm-2 at 77 K, 0 T. A scheme for the regular growth of YBCO on silver was put forward. (author)

  20. 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.

  1. Biaxial and uniaxial data for statistical comparisons of a ceramic's strength

    Science.gov (United States)

    Giovan, M. N.; Sines, G.

    1979-01-01

    The uniaxial and equibiaxial tensile strengths of a brittle material were measured in bending. Equibiaxial tension was attained by concentric ring loading of disks and uniaxial tension by four-point line loading of plates. The two specimen designs give equal volumes, surface areas, and stress gradients. Ground surfaces and lapped surfaces were tested. The equibiaxial tensile strength of a dense alumina was lower than the uniaxial tensile strengths for both ground and lapped surfaces, 8.5 and 8.1%, respectively. The Batdorf theory of flaw statistics, in which biaxial tensile strengths can be predicted from the statistical distribution of uniaxial tensile strength measurements, agreed with the data.

  2. Effectiveness of the modified fatigue criteria for biaxial loading of notched specimen in high-cycle region.

    Czech Academy of Sciences Publication Activity Database

    Major, Št?pán; Hubálovský, Š.; Kocour, Vladimír; Valach, Jaroslav

    Vol. 732. Zürich : Trans Tech Publications, 2015 - (Polach, P.), s. 63-70 ISBN 978-3-03835-413-0. ISSN 1660-9336. [EAN 2014. Conference on experimental stress analysis. /52./. Mariánské Lázn? (CZ), 02.06.2014-05.06.2014] Institutional support: RVO:68378297 Keywords : notched specimen * multiaxial criteria * biaxial loading * fatigue life * bending-torsion loading * high-cycle loading Subject RIV: JM - Building Engineering http://www.scientific.net/AMM.732.63

  3. Deformation modes of nanostructured thin film under controlled biaxial deformation

    OpenAIRE

    Djaziri, Soundes; Faurie, Damien; Le Bourhis, Eric; Goudeau, Philippe; Renault, Pierre-olivier; Mocuta, Christian; Thiaudie?re, Dominique; Hild, Franc?ois

    2013-01-01

    This paper reports on the mechanical behaviour of nanostructured W/Cu thin films deposited on Kapton® under controlled biaxial loadings thanks to a biaxial testing device developed on DiffAbs beamline at SOLEIL synchrotron (Saint-Aubin, France). In situ tensile tests were carried out combining 2D synchrotron x-ray diffraction (XRD) and digital-image correlation (DIC) techniques. First, the elastic behaviour of the composite metallic film-polymeric substrate was investigated under equi-biaxia...

  4. Propagation of short cracks in alloy 800HT and in the steel 22CrMoV12-1 at high temperature under biaxial fatigue

    International Nuclear Information System (INIS)

    For the alloy 800HT and the steel 22 CrMoV 12-1 mode I, mode II and biaxial in-phase fatigue tests were performed on thin-walled tube specimens at temperatures from room temperature to 900 C. Under pure torsion the fatigue life for the same equivalent strain range was found to be always longer than for tensile and biaxial loading. The investigation of surface replicas indicated that crack initiation occurred mainly on grain-boundaries. After initiation stage II crack growth was observed for the tensile and biaxial loading. In torsion, the growth rate was significantly lower and the cracks grew mainly in stage I. Above 800 C stage II crack growth was also found under torsion in Alloy 800HT. For low cycle fatigue the ?J integral if formulated in principal stresses and strains was found to be an appropriate parameter to describe crack growth for all loading conditions. (orig.)

  5. Topology Optimization of Stressed Capacitive RF MEMS Switches

    DEFF Research Database (Denmark)

    Philippine, Mandy A.; Sigmund, Ole

    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-of-plane curling. We use topology optimization to systematically generate designs, by minimizing stress stiffening, minimizing curling, or minimizing stress stiffening while constraining the curling behavior. We present the corresponding problem formulations and sensitivity derivations and discuss the role of key elements in the problem formulation.

  6. Effect of crosslinking density on biaxial relaxation of SBR by using reduced variables. [Styrene-Butadiene Rubber

    Science.gov (United States)

    Arenz, R. J.

    1974-01-01

    The use of reduced variables to account for the effect of crosslinking density in a styrene-butadiene rubber (SBR) system is demonstrated for general biaxial stress states. Recently published results from stress relaxation tests on five SBR vulcanizates crosslinked to different degrees by tetramethylthiuram disulfide were superposed by using the crosslinking density as a reduction variable. The equilibrium shear modulus calculated from the master relaxation curve at long reduced times was in satisfactory agreement with other results for SBR. The time-axis shifts were related in a linear logarithmic manner to the crosslinking density but had a slope slightly less than values previously reported for elastomer systems.

  7. Method of forming biaxially textured alloy substrates and devices thereon

    Science.gov (United States)

    Goyal, Amit (300 Walker Springs Rd., #19E, Knoxville, TN 37923); Specht, Eliot D. (10639 Rivermist La., Knoxville, TN 37922); Kroeger, Donald M. (716 Villa Crest Dr., Knoxville, TN 37923); Paranthaman, Mariappan (1117 Oak Haven Rd., Knoxville, TN 37923)

    2000-01-01

    Specific alloys, in particular Ni-based alloys, that can be biaxially textured, with a well-developed, single component texture are disclosed. These alloys have a significantly reduced Curie point, which is very desirable from the point of view of superconductivity applications. The biaxially textured alloy substrates also possess greatly enhanced mechanical properties (yield strength, ultimate tensile strength) which are essential for most applications, in particular, superconductors. A method is disclosed for producing complex multicomponent alloys which have the ideal physical properties for specific applications, such as lattice parameter, degree of magnetism and mechanical strength, and which cannot be in textured form. In addition, a method for making ultra thin biaxially textured substrates with complex compositions is disclosed.

  8. Depletion-induced biaxial nematic states of boardlike particles

    International Nuclear Information System (INIS)

    With the aim of investigating the stability conditions of biaxial nematic liquid crystals, we study the effect of adding a non-adsorbing ideal depletant on the phase behavior of colloidal hard boardlike particles. We take into account the presence of the depletant by introducing an effective depletion attraction between a pair of boardlike particles. At fixed depletant fugacity, the stable liquid-crystal phase is determined through a mean-field theory with restricted orientations. Interestingly, we predict that for slightly elongated boardlike particles a critical depletant density exists, where the system undergoes a direct transition from an isotropic liquid to a biaxial nematic phase. As a consequence, by tuning the depletant density, an easy experimental control parameter, one can stabilize states of high biaxial nematic order even when these states are unstable for pure systems of boardlike particles. (paper)

  9. Polycrystalline ferroelectric or multiferroic oxide articles on biaxially textured substrates and methods for making same

    Energy Technology Data Exchange (ETDEWEB)

    Goyal, Amit; Shin, Junsoo

    2015-03-31

    A polycrystalline ferroelectric and/or multiferroic oxide article includes a substrate having a biaxially textured surface; at least one biaxially textured buffer layer supported by the substrate; and a biaxially textured ferroelectric or multiferroic oxide layer supported by the buffer layer. Methods for making polycrystalline ferroelectric and/or multiferroic oxide articles are also disclosed.

  10. Method for forming biaxially textured articles by powder metallurgy

    Science.gov (United States)

    Goyal, Amit (Knoxville, TN); Williams, Robert K. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN)

    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.

  11. Planar biaxial characterization of diseased human coronary and carotid arteries for computational modeling.

    Science.gov (United States)

    Kural, Mehmet H; Cai, Mingchao; Tang, Dalin; Gwyther, Tracy; Zheng, Jie; Billiar, Kristen L

    2012-03-15

    Computational models have the potential to provide precise estimates of stresses and strains associated with sites of coronary plaque rupture. However, lack of adequate mathematical description of diseased human vessel wall mechanical properties is hindering computational accuracy. The goal of this study is to characterize the behavior of diseased human coronary and carotid arteries using planar biaxial testing. Diseased coronary specimens exhibit relatively high stiffness (50-210 kPa) and low extensibility (1-10%) at maximum equibiaxial stress (250 kPa) compared to human carotid specimens and values commonly reported for porcine coronary arteries. A thick neointimal layer observed histologically appears to be associated with heightened stiffness and the direction of anisotropy of the specimens. Fung, Choi-Vito and modified Mooney-Rivlin constitutive equations fit the multiaxial data from multiple stress protocols well, and parameters from representative coronary specimens were utilized in a finite element model with fluid-solid interactions. Computed locations of maximal stress and strain are substantially altered, and magnitudes of maximum principal stress (48-65 kPa) and strain (6.5-8%) in the vessel wall are lower than previously predicted using parameters from uniaxial tests. Taken together, the results demonstrate the importance of utilizing disease-matched multiaxial constitutive relationships within patient-specific computational models to accurately predict stress and strain within diseased coronary arteries. PMID:22236530

  12. Computational analysis of fluid flow within a device for applying biaxial strain to cultured cells.

    Science.gov (United States)

    Lee, Jason; Baker, Aaron B

    2015-05-01

    In vitro systems for applying mechanical strain to cultured cells are commonly used to investigate cellular mechanotransduction pathways in a variety of cell types. These systems often apply mechanical forces to a flexible membrane on which cells are cultured. A consequence of the motion of the membrane in these systems is the generation of flow and the unintended application of shear stress to the cells. We recently described a flexible system for applying mechanical strain to cultured cells, which uses a linear motor to drive a piston array to create biaxial strain within multiwell culture plates. To better understand the fluidic stresses generated by this system and other systems of this type, we created a computational fluid dynamics model to simulate the flow during the mechanical loading cycle. Alterations in the frequency or maximal strain magnitude led to a linear increase in the average fluid velocity within the well and a nonlinear increase in the shear stress at the culture surface over the ranges tested (0.5-2.0?Hz and 1-10% maximal strain). For all cases, the applied shear stresses were relatively low and on the order of millipascal with a dynamic waveform having a primary and secondary peak in the shear stress over a single mechanical strain cycle. These findings should be considered when interpreting experimental results using these devices, particularly in the case when the cell type used is sensitive to low magnitude, oscillatory shear stresses. PMID:25611013

  13. Combined experimental and analytical study using cruciform specimen for testing advanced aeropropulsion materials under in-plane biaxial loading

    Science.gov (United States)

    Abdul-Aziz, Ali; Krause, David

    2006-03-01

    A new in-house test capability has been developed at the NASA Glenn Research Center to conduct highly critical tests in support of major and significant components of the Stirling Radioisotope Generator (SRG). It is to aid the development of analytical life prediction methodology and to experimentally assist in verifying the flight-design component's life. Components within the SRG such as the heater head pressure vessel endure a very high temperature environment for a long period of time. Such conditions impose life-limiting failure by means of material creep, a slow gradual increase in strain which leads to an eventual failure of the pressure vessel. To properly evaluate the performance and assist in the design of this component, testing under multiaxial loading setting is essential, since the heater head is subjected to a biaxial state of stress. Thus, the current work undertakes conducting analytical studies under equibiaxial and non-equi-biaxial loadings situations at various temperatures emulating creep environment. These analytical activities will utilize the finite element method to analyze cruciform type specimens both, under linear elastic and creep conditions. And further to calibrate the in-plane biaxial-test system. The specimen finite element model is generated with MSC/Patran [1] and analytical calculations are conducted with MARC and ANSYS finite element codes [2-3]. Complementing these calculations will undertake conducting experimental tests. However, only results pertaining to the analytical studies are reported and their impact on estimating the life of the component is evaluated.

  14. A normalisation procedure for biaxial bias extension tests

    OpenAIRE

    Harrison, P.; Potluri, P.; Bandara, K.; Long, A. C.

    2008-01-01

    Biaxial Bias Extension tests have been performed on a plain-weave carbon fibre engineering fabric. The test results have been normalised using both the upper and lower bound method proposed by Potluri et al. and also using a novel alternative normalisation method based on energy arguments. The normalised results from both methods are compared and discussed.

  15. High Tc YBCO superconductor deposited on biaxially textured Ni substrate

    Science.gov (United States)

    Budai, John D. (Oakridge, TN); Christen, David K. (Oakridge, TN); Goyal, Amit (Knoxville, TN); He, Qing (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Lee, Dominic F. (Knoxville, TN); List, III, Frederick A. (Andersonville, TN); Norton, David P. (Knoxville, TN); Paranthaman, Mariappan (Knoxville, TN); Sales, Brian C. (Knoxville, TN); Specht, Eliot D. (Knoxville, TN)

    1999-01-01

    A superconducting article includes a biaxially-textured Ni substrate, and epitaxial buffer layers of Pd (optional), CeO.sub.2 and YSZ, and a top layer of in-plane aligned, c-axis oriented YBCO having a critical current density (J.sub.c) in the range of at least 100,000 A/cm.sup.2 at 77 K.

  16. Uniaxial and biaxial mechanical properties of porcine linea alba.

    Science.gov (United States)

    Cooney, Gerard M; Moerman, Kevin M; Takaza, Michael; Winter, Des C; Simms, Ciaran K

    2015-01-01

    Incisional hernia is a severe complication post-laparoscopic/laparotomy surgery that is commonly associated with the linea alba. However, the few studies on the mechanical properties of the linea alba in the literature appear contradictory, possible due to challenges with the physical dimensions of samples and variations in protocol. This study focuses on the tensile mechanical characterisation of the porcine linea alba, as determined by uniaxial and equi-load biaxial testing using image-based strain measurement methods. Results show that the linea alba demonstrated a non-linear elastic, anisotropic behaviour which is often observed in biological soft tissues. The transverse direction (parallel to fibres) was found to be approximately eight times stiffer than the longitudinal (cross-fibre) direction under both uniaxial and equi-load biaxial loading. The equi-load biaxial tensile tests revealed that contraction could occur in the transverse direction despite increasing load, probably due to the anisotropy of the tissue. Optical surface marker tracking and digital image correlation methods were found to greatly improve the accuracy of stretch measurement, resulting in a 75% change in the apparent stiffness compared to using strain derived from machine cross-head displacement. Additionally, a finite element model of the experiments using a combination of an Ogden and fibre exponential power law model for the linea alba was implemented to quantify the effect of clamping and tissue dimensions (which are suboptimal for tensile testing) on the results. The preliminary model results were used to apply a correction factor to the uniaxial experimental data prior to inverse optimisation to derive best fit material parameters for the fibre reinforced Ogden model. Application of the model to the equi-load biaxial case showed some differences compared to the experimental data, suggesting a more complex anisotropic model may be necessary to capture biaxial behaviour. These results provide an improved assessment of the mechanical properties of the porcine linea alba for wound closure and other studies. PMID:25460404

  17. Biaxially loaded composite cross-sections

    International Nuclear Information System (INIS)

    The paper presents a general procedure for the stress-strain analysis of composite cross-sections under short-term eccentric longitudinal force. The sections can have an arbitrary form, can be made of various materials, and formed during several stages. The calculation includes the stress-strain analysis, the ultimate bearing capacity determination, and the determination of the required area of the bar reinforcement. The solution of one practical example illustrates the possibility of the model application to dimensioning of reinforced concrete cross-sections. (author)

  18. The design of a biaxial tensile test and its use for the validation of crystallographic yield loci

    Science.gov (United States)

    Hoferlin, E.; Van Bael, A.; Van Houtte, P.; Steyaert, G.; DeMaré, C.

    2000-07-01

    A biaxial tensile test has been designed for the experimental determination of yield locus points of thin steel sheets. Using texture-based anisotropic finite-element simulations, the geometry of the test sample has been optimized. A detailed accuracy analysis is presented and the range of accuracy of the new specimen is derived. Experimental tests have been carried out on a ultra-low carbon and a bake-hardening steel. Both the yield stresses and the ratios of plastic strains have been compared to the theoretical predictions obtained with the Taylor-Bishop-Hill model using the experimentally-determined crystallographic textures.

  19. Stress

    Science.gov (United States)

    ... Some changes are major, such as marriage or divorce, serious illness, or a car accident. Other changes are extreme, such as exposure to violence, and can lead to traumatic stress reactions. How does stress affect the body? Not all stress is bad. All ...

  20. Fatigue behavior of boxing welded joint under biaxial cyclic loads; 2juku kurikaeshi kajuka ni okeru kakumawashi yosetsu keishu no hiro kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, I.; Takada, A.; Akiyama, S.; Ushijima, M.; Maenaka, H. [Ministry of Transportation, Tokyo (Japan)

    1998-12-31

    Various forces such as gravity, wave induced force, inertial force etc. compositely act on a ship body from various directions. Therefore, while discussing strength or life of structural elements of ship body, it is necessary to understand the effects of the composite force condition. In this study, fatigue tests of boxing welded joint under rectangular biaxial cyclic loads are performed, the following results are obtained. Even under he biaxial cyclic loads, it is the same as the uniaxial test, the cracks occurred at the boxing weld toes propagate almost in the straight y-direction, but no oblique propagation of the cracks caused by the lad in the y-direction occurs. That the crack at initial stage of the crack progress is improved in y-direction can be illustrated by the facts that the residual stress in x-direction near the toes reaches to the yield stress, and the stress concentration in the welded toes is bigger in x-direction than that in y-direction. But as for prediction of the progress route, a further study including amplitude ratio of the biaxial loads, effects of width of test specimen is necessary. 4 refs., 12 figs., 4 tabs.

  1. Biaxial fatigue properties of thin-walled composite tubes

    Science.gov (United States)

    Krempl, E.; Elzey, D. M.; Ayar, T.; Loewy, R. G.

    1984-01-01

    A testing method for obtaining fatigue and fracture data under biaxial loading and for negative R-ratios is described. Thin-walled tubes of 1-in. outer nominal diameter with a tapered grip section were tested in an Axial-Torsion Servohydraulic Testing Machine with a 463 Data Control Processor at frequencies below 10 Hz up to the 1-million cycle range. Room temperature, uniaxial constant amplitude fatigue data for high temperature cure graphite-epoxy material are presented at R = -0.4 for a (+, - 5 deg) fiber orientation. The fatigue curve is almost horizontal. Tests on (+, - 5 deg) 'SP-328' resulted in failures which predominantly originated in the grip section. Presently, a new specimen design is being tested intended to eliminate cracking in the grip section. Biaxial in-phase loading of (0/+, - 45) tubes of Fiberite graphite-epoxy resulted in much steeper fatigue curves than observed under uniaxial loading.

  2. Biaxial casting method and apparatus for isolating radioactive waste

    International Nuclear Information System (INIS)

    Hazardous radioactive waste is compacted and cast into safely handled monolithic castings having a radiation barrier wall completely enclosing the radioactive waste by centrifugal casting processes in which the barrier wall may be either a pre-formed shell transported to the jobsite or it may be formed by biaxial centrifugal casting and curing of the barrier wall in a mold. When a pre-formed shell is used, means are provided for thickening the radiation barrier if necessary by biaxial casting of additional barrier material inside of the shell. Castable radioactive material is cast inside the barrier wall before removal of the casting mold from the finished cast monolith. The cast monolith is supported for rotation as the mold is removed therefrom so that additional impact resisting and radiation barrier material can also easily be applied to the exterior surface monolith if radiation leakage exceeds tolerance levels. (author) figs

  3. 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 for either placement method.

  4. Equivalent approaches to alignment tensor dynamics in biaxial liquid crystals

    CERN Document Server

    Close, Alexander R D

    2015-01-01

    Within the framework of liquid crystal flows, the Qian & Sheng (QS) model for Q-tensor dynamics is compared to the Volovik & Kats (VK) theory of biaxial nematics by using Hamilton's variational principle. Under the assumption of rotational dynamics for the Q-tensor, the two approaches are shown to be equivalent in their conservative limit. Also, after presenting a micropolar variant of the VK model, Rayleigh dissipation is included in the treatment.

  5. Uniaxial and biaxial soft deformations of nematic elastomers

    OpenAIRE

    Warner, M.; Kutter, S.

    2001-01-01

    We give a geometric interpretation of the soft elastic deformation modes of nematic elastomers, with explicit examples, for both uniaxial and biaxial nematic order. We show the importance of body rotations in this non-classical elasticity and how the invariance under rotations of the reference and target states gives soft elasticity (the Golubovic and Lubensky theorem). The role of rotations makes the Polar Decomposition Theorem vital for decomposing general deformations int...

  6. Mechanic and electromechanic effects in biaxially stretched liquid crystal elastomers

    OpenAIRE

    Diaz-calleja, Ricardo; Llovera-segovia, Pedro; Riande, Evaristo; Quijano Lo?pez, Alfredo

    2013-01-01

    The effect of combined electromechanic force fields in nematic side chain liquid crystal elastomers will be analyzed. A biaxially stretched plate in the x- and y-directions under an electric field applied in the perpendicular direction to the plate will be considered. A neo-Hookean model is chosen, which implies Gaussian behaviour. Results are obtained for both a soft and semisoft case showing the effect of the electric field on the rotation of the director and the free energy density functio...

  7. Stress.

    OpenAIRE

    Charlton, B. G.

    1992-01-01

    'Stress' is a widely used word in clinical practice, the biological sciences and everyday life; but one which has little real value, serving mainly to confuse and confound rational thought. Whether it is described in terms of stimulus, response, or a combination of the two the definitions of stress are invariably found to be circular. We should stop using the word 'stress' and instead discuss specific stimuli or responses as appropriate. The author suggests that 'pressure' and 'tension' might...

  8. Different stress techniques and their efficiency on triple-gate SOI n-MOSFETs

    Science.gov (United States)

    Bühler, R. T.; Agopian, P. G. D.; Collaert, N.; Simoen, E.; Claeys, C.; Martino, J. A.

    2015-01-01

    Three techniques to implement mechanical stress in n-channel Multiple Gate MOSFETs (MuGFETs) are investigated through 3D simulations and transconductance measurements. They are: uniaxial stress, biaxial stress and biaxial + uniaxial stress. Four different fin dimensions are evaluated: a narrow and a wide transistor, combined with a short or a long device. It is shown that the stress distribution and the device performance exhibit a dependence on the fin dimensions. For uniaxially strained devices, the dimensions are important as the bending of the silicon required to induce stress in the channel depends on its size. However, for biaxially strained devices the plane of etching in the silicon fin is important, determining the degradation of the stress components. The combination of the two types of stress results in an improvement of some stress components and an overall improvement in the maximum transconductance.

  9. Xenon NMR of phase biaxiality in liquid crystals.

    Science.gov (United States)

    Jokisaari, Jukka; Zhu, Jianfeng

    2014-10-01

    Biaxial thermotropic nematic liquid crystals would be of great importance in liquid crystal display technology. Less than a decade ago, such liquid crystals were suggested. The biaxiality of the phases was confirmed using (2)H NMR spectroscopy of deuterated probe molecules. The spectra were collected from a sample rotating around an axis perpendicular to the external magnetic field, resulting in a two-dimensional powder pattern. We have proposed an alternate technique that is based on the second order quadrupole shift detectable in (131)Xe NMR spectra of dissolved xenon. The method has many advantages, such as the NMR spectra are taken from a static sample and the (131)Xe quadrupole coupling tensor is extremely sensitive to the symmetry of the phase. In the present study, we report results obtained on a 600-MHz NMR spectrometer. Together with the data of our earlier study, they confirm that the asymmetry parameter of the (131)Xe quadrupole coupling tensor in the nematic phase of a ferroelectric liquid crystal is 0.85 and in the smectic A phase ca 0.62, indicating significant phase biaxiality. PMID:24771455

  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. The circumferential mechanical properties of bamboo with uniaxial and biaxial compression tests

    OpenAIRE

    Zehui Jiang,; Fuming Chen; Ge Wang; Xing’e Liu; Shi, Sheldon Q.; Hai-tao Cheng

    2012-01-01

    The objective of this study was to investigate the effect of uniaxial and biaxial compression loadings on the circumferential-radial mechanical properties of bamboo. A novel biaxial testing device, called the 3D composite material analysis system, was developed to conduct biaxial compression tests. Strain field analysis was characterized with the help of the digital speckle correlation method (DSCM). The effects of four different environmental treatments (I. air-drying, II. constant temperatu...

  12. Plastic behaviour and forming limit during biaxial compressions of magnesium alloy AZ31 at room temperature

    OpenAIRE

    Shimizu I.; Tada N.

    2010-01-01

    The plastic behaviour and compressive fracture of AZ31 magnesium alloy were examined at room temperature. The uniaxial compression tests and biaxial compression tests along linear and nonlinear strain paths were carried out until fracture using a unique biaxial compression testing machine developed by author. The results revealed the evolution of plastic anisotropy in biaxial compressions, that is the strain path dependency of work hardening. The adaptability of several forming limit cr...

  13. Nonuniversal Critical Behavior at the Uniaxial-Biaxial Nematic Phase Transition in a Lyotropic Mixture

    Science.gov (United States)

    Thieghi, L. T.; Shibli, S. M.; Figueiredo Neto, A. M.; Dmitriev, V. P.; Tolédano, P.

    1998-04-01

    Measurements of the order-parameter critical exponent ? at the uniaxial-biaxial nematic phase transition in a lyotropic mixture are reported. They reveal a strong dependence of ? on the concentration of the mixture compounds with two distinct intervals of values separated by a discontinuity. This nonuniversal behavior is interpreted as the result of three different contributions, which express the micellar biaxiality and the distribution of the micellar population with respect to biaxiality and volume.

  14. Effect of shape biaxiality on the phase behavior of colloidal liquid-crystal monolayers.

    Science.gov (United States)

    González-Pinto, Miguel; Martínez-Ratón, Yuri; Velasco, Enrique; Varga, Szabolcs

    2015-03-01

    We extend our previous work on monolayers of uniaxial particles [J. Chem. Phys., 2014, 140, 204906] to study the effect of particle biaxiality on the phase behavior of liquid-crystal monolayers. Particles are modelled as board-like hard bodies with three different edge lengths ?1 ? ?2 ? ?3, and the restricted-orientation approximation (Zwanzig model) is used. A density-functional formalism based on the fundamental-measure theory is used to calculate phase diagrams for a wide range of values with the largest aspect ratio ?1 = ?1/?3 ? [1,100]. We find that particle biaxiality in general destabilizes the biaxial nematic phase already present in monolayers of uniaxial particles. While plate-like particles exhibit strong biaxial ordering, rod-like ones with ?1 > 21.34 exhibit reentrant uniaxial and biaxial phases. As particle geometry is changed from uniaxial- to increasingly biaxial-rod-like, the region of biaxiality is reduced, eventually ending in a critical-end point. For ?1 > 60, a density gap opens up in which the biaxial nematic phase is stable for any particle biaxiality. Regions of the phase diagram, where packing-fraction inversion occurs (i.e. packing fraction is a decreasing function of density), are found. Our results are compared with the recent experimental studies on nematic phases of magnetic nanorods. PMID:25655742

  15. An engineering method for determining nonproportionality parameter under biaxial fatigue loading

    International Nuclear Information System (INIS)

    Increased requirements to reliability and cost-effectiveness imposed on structural elements of modern machinery, oil, gas, and nuclear industry give rise to the necessity of the modelling of mechanical behavior of vital parts under loading regimes close to operating conditions. The loads occurring in service are in most cases cyclic, multiaxial and nonproportional. Under such conditions, in zones of increased stress concentrations cyclically unstable materials can deform beyond the elastic limit and undergo considerable cyclic hardening. In the region of low-cycle fatigue these factors influence appreciably the lifetime of the material. Thus from fatigue experiments it is known that a 5--10% change in the thin-wall tubular specimen stress state may lead to a change in its lifetime of an order of magnitude and higher. A new engineering method for defining a nonproportionality parameter is proposed for a wide class of cyclic strain paths with a prescribed maximum range of plastic or total strains. This parameter makes it possible to establish an unambiguous linear dependence between the strain path shape and the stress level in a stabilized state under biaxial cyclic loading. Its efficiency was analyzed for predicting the maximum level of hardening for different cycle paths in the space of total and plastic strains

  16. The relation of bifurations in a biaxially loaded rubber sheet and the constitutive modeling of rubber

    Energy Technology Data Exchange (ETDEWEB)

    Haslach, H.W. Jr. [Univ. of Maryland, College Park, MD (United States)

    1995-12-31

    Treloar`s experiments on a thin rubber sheet under in-plane biaxial tensile loads produced asymmetric as well as equal in-plane stretches. At two loads, the two stretches differed by 7.5% and 12.4% respectively. At an intermediate load, there was a stable equal stretches state. Treloar later said that relaxation was negligible since the results were reproducible and independent of the order of force application. Specimen anisotropy and lack of strain uniformity were also eliminated as a cause. Kearsely first pointed out the significance of these experiments to studies of elastic stability of rubber models. The predictability of this result is a test for the validity of the various constitutive models for rubber. First, Ogden`s plane stress stability and bifurcation criteria are reviewed. A coordinate transformation of a generalized energy function for the biaxially loaded sheet makes it possible to describe the Mooney-Rivlin bifurcation as a cusp catastrophe and to verify that the neo-Hookean and other classical models have no bifurcations. The Mooney-Rivlin model predicts unstable equal stretch states above the bifurcation value, but Treloar`s experiments contradict this. These models cannot, then, be the correct constitutive models for rubber. Preliminary ideas on the conditions that an isothermal constitutive model must satisfy to reproduce Treloar`s experiments are proposed. A thermoelastic generalization of the Mooney-Rivlin model, developed with N. N. Zeng, predicts that raising the temperature slightly lowers the value of the bifurcation load. Nonequilibrium processes such as relaxation or sinusoidal loading are modeled using a generalized energy function in place of classical viscoelastic constitutive relations.

  17. Fracture capacity of girth welded pipelines with 3D surface cracks subjected to biaxial loading conditions

    International Nuclear Information System (INIS)

    Offshore pipelines installed by reeling method are subjected to large plastic strains. When the steel pipes are joined by girth welding, both surface and embedded cracks are inevitably initiated in welding zone. The pipe lines should have adequate resistance against both crack extension by tearing and unstable fracture during installation as well as during operation. However, common flaw assessment procedures, e.g. BS 7910:2005 , are not explicitly developed for such situations with large plastic strains. The main objective of the current paper is to find a way to assess fracture capability of a practical pipeline subject to large plastic deformation. In our study, the evolution of crack tip opening displacement (CTOD) of the pipeline with semi-eliptical surface crack in weld girth is investigated under biaxial loading conditions (uniaxial tensile and internal pressure) using three dimensional elastic–plastic finite element analysis. The effects of crack depth, ratio of semi-major axis to semi-minor axis and internal pressure are examined. The results show that at moderate levels of global strain, the variation of CTOD with global strain can be well approximated by a simple linear relationship under tensile loading as well as biaxial loading conditions. Comparing the fracture assessment for the welded pipe made by BS 7910:2005 with that made by our current study, it is found that the assessment from BS7910:2005 is over conservative. A CTOD-estimation method for straative. A CTOD-estimation method for strain -based fracture is suggested for the pipelines when the global strain is 3%. - Highlights: ? 3D FE stress analysis of girth welded pipelines with surface cracks is conducted. ? Both material and geometrical non-linearities are considering in estimating CTOD. ? Existing conservative models result in high rejection rate of welded pipes.

  18. Stress

    Science.gov (United States)

    ... Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook ... stress hormones. Relaxing can help by blunting this sensitivity. There are many ways to help yourself relax: ...

  19. Sol-gel deposition of buffer layers on biaxially textured metal substances

    Science.gov (United States)

    Shoup, Shara S. (Woodstock, GA); Paranthamam, Mariappan (Knoxville, TN); Beach, David B. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Goyal, Amit (Knoxville, TN)

    2000-01-01

    A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.

  20. Thermotropic biaxial nematics: [1] highly desirable materials, still elusive?

    Scientific Electronic Library Online (English)

    Klaus, Praefcke.

    2002-06-01

    Full Text Available SciELO Brazil | Language: English Abstract in english On the basis and with the inclusion of results described in a previous paper [2], submitted for publication almost two years ago, we add some comments on very recent developments regarding both the design and synthesis of thermotropic nematogens of low-molecular weight, supposed biaxial in character [...] , as well as puzzles, still unsolved, with methods of their unambiguous identification. In general, this update may demonstrate the complexity and problematic nature inherent in this topical subject of research indicated by a struggle over a very relevant, but very difficult matter.

  1. 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.

  2. 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.

  3. 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)

  4. Biaxial creep strains at notch roots -- Measurement and modeling

    International Nuclear Information System (INIS)

    Creep and creep-fatigue interaction effects have become increasingly important at higher operating temperatures of power generating systems. The cooling tubes in pressurized heavy water nuclear reactors are examples of components where these effects may be critical. Here, biaxial strains were measured at the roots of single notches in zirconium alloy specimens under loading and creep conditions (up to 1200 hours) at 250 C. A laser-based interferometric technique was used; details of the measurement procedures are given in another paper. Here, the Bodner model is incorporated into the ABAQUS finite element code and used to predict the biaxial strains at the notch root during loading and for a creep duration of 100 hours. The strains during loading agree quite well with the measured ones while the predicted creep strains are smaller. This discrepancy is attributed to the lack of precision in determining the constants for the Bodner model from smooth-specimen tests. Both the measurement technique and the Bodner model are well-suited for studies of notch response

  5. 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 ?m. 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.

  6. Method of depositing buffer layers on biaxially textured metal substrates

    Science.gov (United States)

    Beach, David B. (Knoxville, TN); Morrell, Jonathan S. (Knoxville, TN); Paranthaman, Mariappan (Knoxville, TN); Chirayil, Thomas (Knoxville, TN); Specht, Eliot D. (Knoxville, TN); Goyal, Amit (Knoxville, TN)

    2002-08-27

    A laminate article comprises a substrate and a biaxially textured (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer over the substrate, wherein 0biaxially textured metal, such as nickel. A method of forming the laminate article is also disclosed.

  7. Biaxial optical anisotropy of self aligned silver nanoparticles and nanowires

    International Nuclear Information System (INIS)

    In the present study ion beam sputtering has been used for pre-structuring of a silicon substrate followed deposition of metal by e-beam evaporation. First a low energy ion beam (Ar+, 500 eV) is incident on the substrate surface at an angle of 67 to the surface normal to produce well ordered (20-50 nm) ripple patterns. Then physically vaporized Ag atoms are deposited at grazing angle of 70 to the surface normal and normal to the ripples direction. Varying deposition parameters, i.e. ripple periodicity, substrate temperature and atomic flux, we were able to produce well ordered nanoparticles and nanowires. Self-aligned Ag nanoparticles and nanowires deposited on pre-patterned ripple surfaces exhibit strong optical anisotropy. Generalised ellipsometry measurements show that off diagonal Jones matrix elements (?ps, ?ps, ?sp, ?sp) are non zero and vary with Eulers angle ?. This indicates that such a medium is biaxial in nature. A biaxial layer model approach is used to calculate dielectric functions for such a system. Tauc-Lorentz oscillators are used along x and y direction independently and Drude model along z-direction for nanoparticles. This approach provides a very good fitting with the measured Jones matrix element ?pp, ?pp, ?ps, ?ps, ?sp, ?sp. Different cases for ordered nanoparticles and wires are presented.ted.

  8. Powder-in-tube and thick-film methods of fabricating high temperature superconductors having enhanced biaxial texture

    Science.gov (United States)

    Goyal, Amit; Kroeger, Donald M.

    2003-11-11

    A method for forming an electronically active biaxially textured article includes the steps of providing a substrate having a single crystal metal or metal alloy surface, deforming the substrate to form an elongated substrate surface having biaxial texture and depositing an epitaxial electronically active layer on the biaxially textured surface. The method can include at least one annealing step after the deforming step to produce the biaxially textured substrate surface. The invention can be used to form improved biaxially textured articles, such as superconducting wire and tape articles having improved J.sub.c values.

  9. Effect of biaxiality in creep-fatigue at elevated temperatures. Annual report, January 1, 1974--December 31, 1974

    International Nuclear Information System (INIS)

    The effect of biaxiality in creep-fatigue interaction at elevated temperature is being investigated. Biaxial fatigue tests were conducted with thin-walled tubular specimens loaded with axial tension-compression and torsion. Biaxial strains were imposed under synchronous loading condition at 25 cycles per minute. Specimens were obtained from extruded 304 stainless steel rods, machined to specifications and annealed in an argon atmosphere at 20000F. The experimental data covers uniaxial and biaxial fatigue tests at 10000F and uniaxial and biaxial cumulative fatigue damage tests under a high to low loading sequence at 1000 and 12000F. (U.S.)

  10. The circumferential mechanical properties of bamboo with uniaxial and biaxial compression tests

    Directory of Open Access Journals (Sweden)

    Zehui Jiang

    2012-11-01

    Full Text Available The objective of this study was to investigate the effect of uniaxial and biaxial compression loadings on the circumferential-radial mechanical properties of bamboo. A novel biaxial testing device, called the 3D composite material analysis system, was developed to conduct biaxial compression tests. Strain field analysis was characterized with the help of the digital speckle correlation method (DSCM. The effects of four different environmental treatments (I. air-drying, II. constant temperature and relative humidity, III. relatively low temperature, and IV. ultra-low temperature on the circumferential performance of bamboo were examined in the experiment. The results of this study indicated that the diametric strength of bamboo evaluated by biaxial load was as 2.4 to 2.5 times the uniaxial compression. Under biaxial load, the strength of the bamboo node was about 2.38 times higher than the internode. Failure first occurred at the outside surface of bamboo at about the 45° position between X and Y axial when conducting a biaxial compression test. The distribution of X-strain field expressed itself more uniformly than the Y-strain field. The diametric mechanical properties of bamboo ring were ?IV>?III>?II>?I for both the uniaixal and biaxial compression tests.

  11. Tuning biaxiality of nematic phases of board-like colloids by an external magnetic field.

    Science.gov (United States)

    Leferink op Reinink, Anke B G M; Belli, Simone; van Roij, René; Dijkstra, Marjolein; Petukhov, Andrei V; Vroege, Gert Jan

    2014-01-21

    We study the influence of a magnetic field on the biaxial nematic phase of board-like goethite colloids both experimentally and theoretically. Using synchrotron small angle X-ray scattering techniques we find that applying a magnetic field along the main director of the biaxial nematic phase leads to a clear decrease in biaxiality with increasing magnetic field strength. Above a certain magnetic field strength the biaxiality is completely suppressed and the biaxial nematic phase transforms into an ordinary prolate uniaxial nematic phase. In order to interpret the physical mechanism behind this phenomenon, we develop a mean-field theory for the liquid crystal phase behaviour of the suspension. Within this theory the magnetic properties of the particles are modelled by taking into account the effect of both the permanent and the induced magnetic dipoles. The resulting phase diagrams support our experimental findings of the field-induced biaxial nematic to prolate uniaxial nematic transition. They additionally predict that for more plate-like particles, which initially would only display oblate nematic ordering of the shortest axis, the rare biaxial phase can be induced by applying a magnetic field with a carefully chosen field strength, a parameter which can be easily tuned. PMID:24652631

  12. Effect of biaxial strain on the magnetism of Fe16N2: Density-functional investigations

    International Nuclear Information System (INIS)

    The effect of biaxial strain on the magnetism of ??-Fe16N2 was investigated by the first principles calculations. The GGA, GGA + U and HSE06 calculations give the same result that the magnetic moments increase with the biaxial strain in the ab plane. All non-equivalent Fe atoms contribute to the increase of magnetic moments, although the variations of inter-atomic distances between non-equivalent Fe and N are different. Additionally, the magnetic anisotropy of Fe16N2 could be controlled by the biaxial strain.

  13. Revealing the uniaxial to biaxial nematic liquid crystal phase transition via distinctive electroconvection

    Science.gov (United States)

    Xiang, Ying; Goodby, J. W.; Görtz, V.; Gleeson, H. F.

    2009-05-01

    Electroconvection (EC) phenomena are reported in the uniaxial and biaxial nematic phases of a bent-core liquid crystal. Two EC instabilities are observed. Prewavy_1, which exists only in the uniaxial phase, has stripes parallel to the rubbing direction, a periodicity of order of the device thickness, and an onset voltage that diverges near the uniaxial to biaxial transition. The prewavy_2 instability, characterized by stripes perpendicular to the rubbing direction and a periodicity of twice the device thickness, exists across the entire nematic regime. Our observations are explained through changes in the electrical conductivity anisotropy at the uniaxial to biaxial transition.

  14. Applicability of a particularly simple model to nonlinear elasticity of slide-ring gels with movable cross-links as revealed by unequal biaxial deformation

    Science.gov (United States)

    Kondo, Yuuki; Urayama, Kenji; Kidowaki, Masatoshi; Mayumi, Koichi; Takigawa, Toshikazu; Ito, Kohzo

    2014-10-01

    The strain energy density function (F) of the polyrotaxane-based slide-ring (SR) gels with movable cross-links along the network strands is characterized by unequal biaxial stretching which can achieve various types of deformation. The SR gels as prepared without any post-preparation complication exhibit considerably smaller values of the ratio of the stresses (?y/?x) in the stretched (x) and constrained (y) directions in planar extension than classical chemical gels with heterogeneous and nearly homogeneous network structures do. This feature of the SR gels leads to the peculiar characteristic that the strain energy density function (F) has no explicit cross term of strains in different directions, which is in contrast to F with explicit strain cross terms for most chemical gels and elastomers. The biaxial stress-strain data of the SR gels are successfully described by F of the Gent model with only two parameters (small-strain shear modulus and a parameter representing ultimate elongation), which introduces the finite extensibility effect into the neo-Hookean model with no explicit cross term of strain. The biaxial data of the deswollen SR gels examined in previous study, which underwent a considerable reduction in volume from the preparation state, are also well described by the Gent model, which is in contrast to the case of the classical chemical gels that the stress-strain relations before and after large deswelling are not described by a common type of F due to a significant degree of collapse of the network strands in the deswollen state. These intriguing features of nonlinear elasticity of the SR gels originate from a novel function of the slidable cross-links that can maximize the arrangement entropy of cross-linked and non-cross-linked cyclic molecules in the deformed networks.

  15. Methods for using 3-d ultrasound speckle tracking in biaxial mechanical testing of biological tissue samples.

    Science.gov (United States)

    Yap, Choon Hwai; Park, Dae Woo; Dutta, Debaditya; Simon, Marc; Kim, Kang

    2015-04-01

    Being multilayered and anisotropic, biological tissues such as cardiac and arterial walls are structurally complex, making the full assessment and understanding of their mechanical behavior challenging. Current standard mechanical testing uses surface markers to track tissue deformations and does not provide deformation data below the surface. In the study described here, we found that combining mechanical testing with 3-D ultrasound speckle tracking could overcome this limitation. Rat myocardium was tested with a biaxial tester and was concurrently scanned with high-frequency ultrasound in three dimensions. The strain energy function was computed from stresses and strains using an iterative non-linear curve-fitting algorithm. Because the strain energy function consists of terms for the base matrix and for embedded fibers, spatially varying fiber orientation was also computed by curve fitting. Using finite-element simulations, we first validated the accuracy of the non-linear curve-fitting algorithm. Next, we compared experimentally measured rat myocardium strain energy function values with those in the literature and found a matching order of magnitude. Finally, we retained samples after the experiments for fiber orientation quantification using histology and found that the results satisfactorily matched those computed in the experiments. We conclude that 3-D ultrasound speckle tracking can be a useful addition to traditional mechanical testing of biological tissues and may provide the benefit of enabling fiber orientation computation. PMID:25616585

  16. A resonant biaxial Helmholtz coil employing a fractal capacitor bank

    Science.gov (United States)

    Martin, James E.

    2013-09-01

    The design and construction of a series resonant biaxial Helmholtz coil for the production of magnetic fields as large as 500 G in the range of 100-2500 Hz is described. Important aspects of ac coil design are discussed, including: minimizing power losses due to the expected Joule heating, self-induced eddy currents, and skin resistance; controlling the stray capacitance; maximizing field homogeneity; and keeping peak voltages at acceptable levels. The design and construction of a computer-controlled, optically isolated fractal capacitor bank is then treated, and various aspects of capacitor selection and characterization were discussed. The system performance is demonstrated, including stability and the possibility of field component dephasing with typical magnetic samples.

  17. Conductive layer for biaxially oriented semiconductor film growth

    Science.gov (United States)

    Findikoglu, Alp T. (Los Alamos, NM); Matias, Vladimir (Santa Fe, NM)

    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.

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

    International Nuclear Information System (INIS)

    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 refraction properties 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 results are given to validate our theoretical analysis

  19. The effect of the stress far field on the crack tip behaviour

    Directory of Open Access Journals (Sweden)

    A. PIVA

    1979-06-01

    Full Text Available The boundary value problem of an infinite purely elastic sheet with
    a traction-free crack loaded with a uniform shear and biaxial tension at
    infinity is solved. It is shown that the singular terms of stress and displacement functions are inadequate to predict the direction of initial crack extension. The independence of the J vector of the biaxial parameter is also proved.

  20. Effects of pre-annealing on the uni- and bi-axial stretching behavior of poly(ethylene naphthalate) films

    Energy Technology Data Exchange (ETDEWEB)

    Abe, T., E-mail: kikutani.t.aa@m.titech.ac.jp; Takarada, W., E-mail: kikutani.t.aa@m.titech.ac.jp; Kikutani, T., E-mail: kikutani.t.aa@m.titech.ac.jp [Dept. Organic and Polymeric Materials, Tokyo Institute of Technology (Japan)

    2014-05-15

    Effect of pre-annealing on stress and birefringence behavior of poly(ethylene naphthalate) (PEN) films during stretching and relaxation processes was investigated. Amorphous and non-oriented PEN films were pre-annealed under the conditions of different temperatures and periods. The pre-annealed films were stretched uniaxially or equi-biaxially and then relaxed at fixed length. It was found that pre-annealing did not cause any notable change for the initial behavior of refractive indices variation, whereas the behaviors after necking were significantly affected. Through the comparison between in-plane and out-of-plane birefringence and the analysis of wide-angle x-ray diffraction patterns of drawn films of both stretching modes, it was confirmed that the orientation of naphthalene ring in the film plane was enhanced by pre-annealing.

  1. Effects of pre-annealing on the uni- and bi-axial stretching behavior of poly(ethylene naphthalate) films

    International Nuclear Information System (INIS)

    Effect of pre-annealing on stress and birefringence behavior of poly(ethylene naphthalate) (PEN) films during stretching and relaxation processes was investigated. Amorphous and non-oriented PEN films were pre-annealed under the conditions of different temperatures and periods. The pre-annealed films were stretched uniaxially or equi-biaxially and then relaxed at fixed length. It was found that pre-annealing did not cause any notable change for the initial behavior of refractive indices variation, whereas the behaviors after necking were significantly affected. Through the comparison between in-plane and out-of-plane birefringence and the analysis of wide-angle x-ray diffraction patterns of drawn films of both stretching modes, it was confirmed that the orientation of naphthalene ring in the film plane was enhanced by pre-annealing

  2. 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...

  3. Method of deforming a biaxially textured buffer layer on a textured metallic substrate and articles therefrom

    Science.gov (United States)

    Lee, Dominic F. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Goyal, Amit (Knoxville, TN)

    2000-01-01

    The present invention provides methods and biaxially textured articles having a deformed epitaxial layer formed therefrom for use with high temperature superconductors, photovoltaic, ferroelectric, or optical devices. A buffer layer is epitaxially deposited onto biaxially-textured substrates and then mechanically deformed. The deformation process minimizes or eliminates grooves, or other irregularities, formed on the buffer layer while maintaining the biaxial texture of the buffer layer. Advantageously, the biaxial texture of the buffer layer is not altered during subsequent heat treatments of the deformed buffer. The present invention provides mechanical densification procedures which can be incorporated into the processing of superconducting films through the powder deposit or precursor approaches without incurring unfavorable high-angle grain boundaries.

  4. Biaxial monogenic functions from Funk-Hecke's formula combined with Fueter's theorem

    OpenAIRE

    Pen?a, Dixan Pen?a; Sommen, Frank

    2014-01-01

    Funk-Hecke's formula allows a passage from plane waves to radially invariant functions. It may be adapted to transform axial monogenics into biaxial monogenics that are monogenic functions invariant under the product group SO(p)xSO(q). Fueter's theorem transforms holomorphic functions in the plane into axial monogenics, so that by combining both results, we obtain a method to construct biaxial monogenics from holomorphic functions.

  5. Phase biaxiality in nematic liquid crystalline side-chain polymers of various chemical constitutions.

    Science.gov (United States)

    Severing, Kirsten; Stibal-Fischer, Elke; Hasenhindl, Alfred; Finkelmann, Heino; Saalwächter, Kay

    2006-08-17

    In a previous deuterium NMR study conducted on a liquid crystalline (LC) polymer with laterally attached book-shaped molecules as the mesogenic moiety, we have revealed a biaxial nematic phase below the conventional uniaxial nematic phase (Phys. Rev. Lett. 2004, 92, 125501). To elucidate details of its formation, we here report on deuterium NMR experiments that have been conducted on different types of LC side-chain polymers as well as on mixtures with low-molar-mass mesogens. Different parameters that affect the formation of a biaxial nematic phase, such as the geometry of the attachment, the spacer length between the polymer backbone and the mesogenic unit, as well as the polymer dynamics, were investigated. Surprisingly, also polymers with terminally attached mesogens (end-on polymers) are capable of forming biaxial nematic phases if the flexible spacer is short and thus retains a coupling between the polymer backbone and the LC phase. Furthermore, the most important parameter for the formation of a biaxial nematic phase is the dynamics of the polymer backbone, as the addition of a small percentage of low molar mass LC to the biaxial nematic polymer from the original study served to shift both the glass transition and the appearance of detectable biaxiality in a very similar fashion. Plotting different parameters for the investigated systems as a function of T/Tg also reveals the crucial role of the dynamics of the polymer backbone and hence the glass transition. PMID:16898711

  6. 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.

  7. Combined synchrotron X-rays and image correlation analyses of biaxially deformed W/Cu nanocomposite thin films on Kapton

    OpenAIRE

    Djaziri, Soundes; Renault, Pierre-olivier; Hild, Franc?ois; Le Bourhis, Eric; Goudeau, Philippe; Thiaudie?re, Dominique; Faurie, Damien

    2011-01-01

    Abstract In-situ biaxial tensile tests within the elastic domain were conducted with W/Cu nanocomposite thin films deposited on a polyimide cruciform substrate thanks to a biaxial testing machine developed on the DiffAbs beamline at SOLEIL synchrotron. The mechanical behavior of the nanocomposite was characterized at the micro-scale and the macro-scale using simultaneously synchrotron X-ray diffraction and digital image correlation techniques. Strain analyses for equi-biaxial and non equi-bia...

  8. Investigation of the influence of multiaxial stress states and material anisotropy on the residual stress measurement according to the hole drilling method

    International Nuclear Information System (INIS)

    Numerical calculations and experimental results indicate that applying uniaxial formalism to two-dimensional stress states leads to considerable errors. A biaxial formalism is presented which gives in such cases precise values for residual stresses. For extremely anisotropic materials no generally applicable formalism can be derived. However, in the case of small degrees of texture the expected errors are marginal. (orig.)

  9. Anisotropically biaxial strain in a-plane AlGaN on GaN grown on ?-plane sapphire

    International Nuclear Information System (INIS)

    In this study, the anisotropically biaxial strain in a-plane AlGaN on GaN is investigated by X-ray diffraction (XRD) analysis using an AlGaN/GaN heterostructure grown on r-plane sapphire. In accordance with XRD reciprocal lattice space mapping, when the AlN molar fraction x in the AlGaN layer is 0.18, the AlGaN layer is fully strained under tensile stress and grows coherently on the underlying GaN layer. However, when x is as large as 0.31, partial relaxation is observed only in the c-axis direction. The tensile stress in the AlGaN layer is calculated taking the actual in-plane lattice constants of the underlying GaN layer into account, and it was found that the stress in the a-plane AlGaN layer in the c-axis direction is approximately 1.7 times lager than that in the m-axis direction. (author)

  10. 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...

  11. Strain rate-dependent flow stress curves in the large deformation range

    Science.gov (United States)

    Bae, Gihyun

    2013-12-01

    This paper deals with the construction method of the flow stress curve at various strain rates in the large deformation range. The hydraulic bulge test is carried out for EDDQ and 590DP steel sheets in order to obtain equibiaxial flow stress curves according to the punch speed. By using the measured curves, the stress data at various plastic strains is fitted by Cowper-Symonds model in order to analyze the strain rate sensitivity and determine the stress value at the designated strain rate. Equi-biaxial flow stress curves at various strain rates are constructed by fitting the determined stress value with Swift model with respect to the plastic strain. Finally, equi-biaxial flow stress curves are converted into uniaxial flow stress curves by using Yld2000-2d yield function. A suggested procedure can be utilized to construct the uniaxial flow stress curves at various strain rates in the large deformation range.

  12. 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

  13. Failure analysis based on microvoid growth for sheet metal during uniaxial and biaxial tensile tests

    International Nuclear Information System (INIS)

    Highlights: ? Cruciform specimen designed and biaxial tensile test carried out. ? Stereo Correlation Image technique is used for 3D full-filed measurements. ? SEM fractography analysis is used to explain the fracture mechanism. ? Constitutive modeling of the necking phenomenon was developed using GTN model. - Abstract: The aim of the presented investigations is to perform an analysis of fracture and instability during simple and complex load testing by addressing the influence of ductile damage evolution in necking processes. In this context, an improved experimental methodology was developed and successfully used to evaluate localization of deformation during uniaxial and biaxial tensile tests. The biaxial tensile tests are carried out using cruciform specimen loaded using a biaxial testing machine. In this experimental investigation, Stereo-Image Correlation technique has is used to produce the heterogeneous deformations map within the specimen surface. Scanning electron microscope is used to evaluate the fracture mechanism and the micro-voids growth. A finite element model of uniaxial and biaxial tensile tests are developed, where a ductile damage model Gurson–Tvergaard–Needleman (GTN) is used to describe material deformation involving damage evolution. Comparison between the experimental and the simulation results show the accuracy of the finite element model to predict the instability phenomenon. The advanced measurement techniques contribute to understand better the ductile fracture mechanism

  14. 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.

  15. Biaxial Orientation Characterization in PE and PP Using WAXD X-Ray Pole Figures, FTIR Spectroscopy, and Birefringence

    OpenAIRE

    Ajji, A.; Elkoun, S.; Zhang, X.

    2005-01-01

    Abstract In this study, different polyethylene and polypropylene films (LDPE, LLDPE, HDPE, and PP) are produced using different processes (film blowing and biaxial orientation) and processing conditions. The orientation of the films is characterized in terms of their biaxial crystalline, amorphous, and global orientation factors using birefringence, Fourier transform infrared spectroscopy (FTIR) using a til...

  16. The self-propelled Brownian spinning top: dynamics of a biaxial swimmer at low Reynolds numbers

    CERN Document Server

    Wittkowski, Raphael

    2011-01-01

    Recently, the Brownian dynamics of self-propelled (active) rod-like particles was explored to model the motion of colloidal microswimmers, catalytically-driven nanorods, and bacteria. Here, we generalize this description to biaxial particles with arbitrary shape and derive the corresponding Langevin equation for a self-propelled Brownian spinning top. The biaxial swimmer is exposed to a hydrodynamic Stokes friction force at low Reynolds numbers, to fluctuating random forces and torques as well as to an external and an internal (effective) force and torque. The latter quantities control its self-propulsion. Due to biaxiality and hydrodynamic translational-rotational coupling, the Langevin equation can only be solved numerically. In the special case of an orthotropic particle in the absence of external forces and torques, the noise-free (zero-temperature) trajectory is analytically found to be a circular helix. This trajectory is confirmed numerically to be more complex in the general case involving a transient...

  17. The Relationship Between Microstructure and Toughness of Biaxially Oriented Semicrytalline Polyester Films

    International Nuclear Information System (INIS)

    The relationship between microstructure and toughness of biaxially stretched semicrystalline polyester films was investigated. Optically transparent films were prepared by simultaneous biaxial stretching of melt-cast sheets near the glass transition temperature. Copolyesters of polyethylene terephthalate (PET) with different compositions of two diols: ethylene glycol (EG) and cyclohexane dimethanol (CHDM), and stoichiometrically matched terephthalic acid were used to produce films with different degrees of crystallinity. In addition, the PET films with different crystalline morphologies were produced by constrained high temperature annealing of biaxially oriented films. The toughness, degree of crystallinity and crystalline morphology/molecular ordering were studied using mechanical testing, synchrotron small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD) techniques, and differential scanning calorimetry (DSC). The results indicate that the toughness of a semicrystalline polymeric film is determined by the interconnectivity of the crystalline phase within the amorphous phase and is greatly influenced by the degree of crystallinity and the underlying crystalline morphology.

  18. Strain distribution and Raman spectroscopy in individual Ge/CdSe biaxial nanowires

    Science.gov (United States)

    Wang, Dong; Wang, Chunrui; Xu, Jing; Wu, Binhe; Ouyang, Lizhi; Parthasarathy, Ranganathan; Chen, Xiaoshuang

    2015-02-01

    The interface property modulated by strain is one of the key factors that determine the performance of heterostructure nanowire devices. In this study, the strain distribution in a Ge/CdSe biaxial nanowire was calculated by a finite element method using boundary conditions. The components of the strain tensor of the biaxial nanowire show different characteristics from those of core–shell nanowires. The relationship between the strain and Raman mode of a Ge sub-nanowire is then revealed. The calculated and measured Raman modes of a Ge sub-nanowire in a Ge/CdSe biaxial nanowire have the same variation in redshift and wide peak as those of unstrained Ge nanowires.

  19. Device and method of optically orienting biaxial crystals for sample preparation

    Science.gov (United States)

    Thomas, Timothy; Rossman, George R.; Sandstrom, Mark

    2014-09-01

    An optical instrument we refer to as the "biaxial orientation device" has been developed for finding the optical plane, acute bisectrix, and obtuse bisectrix in biaxial crystals by means of optically aligning conoscopically formed melatopes and measuring the angular coordinates of the melatopes, where the angular values allow for determination of the optical plane containing the optical axes using a vector algebra approach. After determination of the optical plane, the instrument allows for the sample to be aligned in the acute bisectrix or obtuse bisectrix orientations and to be transferred to a simple mechanical component for subsequent grinding and polishing, while preserving the orientation of the polished faces relative to the optical plane, acute bisectrix, and obtuse bisectrix during the grinding and polishing process. Biaxial crystalline material samples prepared in the manner are suitable for accurate spectroscopic absorption measurements in the acute bisectrix and obtuse bisectrix directions as well as perpendicular to the optical plane.

  20. Solutions of the second elastic–plastic fracture mechanics parameter in test specimens under biaxial loading

    International Nuclear Information System (INIS)

    Extensive finite elements analyses have been conducted to obtain solutions of the A-term, which is the second parameter in a three-term elastic–plastic asymptotic expansion, for test specimens under biaxial loading. Three mode I plane-strain test specimens, i.e. single edge cracked plate (SECP), center cracked plate (CCP) and double edge cracked plate (DECP) were studied. The crack geometries analyzed include shallow to deep cracks, and the biaxial loading ratios analyzed are 0.5 and 1.0. Solutions of A-term were obtained for materials following the Ramberg–Osgood power law with hardening exponent of n = 3, 4, 5, 7 and 10. Remote tension loading was applied which covers from small-scale to large-scale yielding. Based on the finite element results, effects of biaxial loading on crack tip constraint were discussed. Empirical equations to predict the A-term under small-scale yielding to fully-plastic condition were developed using estimation methods developed earlier. Based on the relationships between A and other commonly-used second fracture parameter Q and A2, the present solutions can be used to calculate parameters Q and A2 as well. The results presented in the paper are suitable to determine the second elastic–plastic fracture parameters for test specimens for a wide range of crack geometries, material strain hardening behaviors under biaxial loading conditions. -- Highlights: • Elastic–plastic finite element analyses were conducted to obtain A-term for three test specimens under biaxial loading. • Solutions cover wide range of crack depth, material nonlinearity and from small scale yielding to large scale yielding. • It is demonstrated that biaxial loading has significant effect on crack tip constraint. • Three estimation methods were used to obtain empirical equations of A for engineering applications. • Solutions of A can be easily converted to get Q and A2 solutions

  1. 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

  2. NESC VII: a European project for application of WPS in RPV assessment including biaxial loading

    Energy Technology Data Exchange (ETDEWEB)

    Moinereau, D. (EDF R and D, Materials and Mechanics of Components Dept., Moret-sur-Loing (France)), e-mail: dominique.moinereau@edf.fr; Gilles, P. (AREVA NP SAS, Paris La Defense (France)); Chapuliot, S. (CEA, Gif-sur-Yvette (France))

    2009-07-01

    A full description of the NESC VII project is presented. Based on experimental, analytical and numerical tasks, the project is focused on topics generally non covered by past experience on WPS: biaxiality of loading on large-scale specimens, effect of irradiation, applicability to intergranular fracture, modeling (including analytical and numerical models). Among these tasks, some new original WPS experiments will be conducted on large scale cruciform bend bar specimens in order to study the influence of biaxial loading on WPS effect, using a fully representative RPV steel (18MND5 steel similar to A533B steel)

  3. 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

  4. Production and transformation of ring light beams by means of biaxial crystals

    Science.gov (United States)

    Ryzhevich, Anatol A.; Katranji, Evgeni G.; Mashchenko, Aleksander G.

    2001-03-01

    Universal method, permitting to form multi-ring light beams with a required quantity of rings from the circularly polarized Gaussian light beam, is proposed. This method permits to increase or decrease by 1 the order of an input beam wavefront screw dislocation, if beam has it. The method was realized by means of the optical scheme containing a biaxial crystal. Using biaxial KTP and (alpha) -HIO3 (iodic acid) crystals Bessel and multi-ring light beams with the first and the second order dislocations are obtained experimentally. The second harmonic generation by mono-, two- and four-ring light beams possessing WFSD1 in a nonlinear KTP crystal is studied experimentally.

  5. Biaxial High Cycle Fatigue of a type 304L stainless steel: Cyclic strains and crack initiation detection by digital image correlation

    International Nuclear Information System (INIS)

    A series of biaxial High Cycle Fatigue tests at room temperature is performed to build up an extensive and well-documented database. The testing specimen is a maltese cross thinned in its centre with non-homogeneous strain/stress fields. The experimental protocol uses exclusively full-field strain measurements. The strains (cyclic and residual) as well as the crack initiation detection are obtained by use of Digital Image Correlation (DIC) techniques combined with a multi-scale stroboscopic image acquisition in-situ set-up. Nine cruciform specimens made of type 304L austenitic stainless steel are loaded by a multiaxial testing machine. Two kinds of loading paths are presented: equi-biaxial with a load ratio of 0.1, non-proportional with a cyclic load in one direction and a constant load in the other. The experimental results are given (strain amplitude, residual strain, number of cycles to crack initiation) for each loading path. The time history of local strain amplitudes and residual strains are recorded and plotted. Total strain vs. number of cycles fatigue curves show the different trends associated with each loading path. For instance, non-proportional loadings are found very damaging and leading to strong ratchetting effects. The tested material is briefly introduced, followed by an in-depth description of the experimental set-up. The fatigue test campaign results are then presented, with a final discussion. (authors)

  6. Gyrocompassing of a biaxial gyrostabilizer with a nonvertical axis of stabilization

    Science.gov (United States)

    Meleshko, V. V.

    1988-01-01

    The possibility of the gyrocompassing of a biaxial gyrostabilizer with a nonvertical axis of stabilization on a stationary platform is demonstrated analytically. Expressions are obtained which relate the gyrostabilizer characteristics to the precision and time of gyrocompassing. The validity of the assumptions made in the analysis is verified through a computer simulation of gyrostabilizer motion.

  7. In situ biaxial rotation at low-temperatures in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Selby, N. S., E-mail: nselby3@gatech.edu [Sandia National Labs, Albuquerque, New Mexico 87185 (United States); Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Crawford, M. [Sandia National Labs, Albuquerque, New Mexico 87185 (United States); Department of Mechanical Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Tracy, L.; Reno, J. L.; Pan, W. [Sandia National Labs, Albuquerque, New Mexico 87185 (United States)

    2014-09-15

    We report the design, construction, and characterization of a biaxial sample rotation stage for use in a cryogenic system for orientation-dependent studies of anisotropic electronic transport phenomena at low temperatures and high magnetic fields. Our apparatus allows for continuous rotation of a sample about two axes, both independently and simultaneously.

  8. Simple expressions for transmission and reflection matrix elements of a biaxial thin layer at normal incidence.

    Science.gov (United States)

    Cojocaru, E

    1999-04-01

    The extended Jones matrix method is applied for determination of the transmission and reflection matrices for a normally incident plane wave upon an homogeneous and lossless biaxial thin layer. The elements of these matrices are expressed by simple analytical relations. By using these relations one can express analytically the polarization-dependent optical parameters to be determined by generalized ellipsometry. PMID:18319763

  9. Biaxial loading and shallow-flaw effects on crack-tip constraint and fracture-toughness

    International Nuclear Information System (INIS)

    Uniaxial tests of single-edged notched bend (SENB) specimens with both deep- and shallow-flaws have shown elevated fracture-toughness for the shallow flaws. The elevation in fracture-toughness for shallow flaws has been shown to be the result of reduced constraint at the crack-tip. Biaxial loading has the potential to increase constraint at the crack-tip and thereby reduce some of the shallow-flaw, fracture-toughness elevation. Biaxial fracture-toughness tests have shown that the shallow-flaw, fracture-toughness elevation is reduced but not eliminated by biaxial loading. Dual-parameter, fracture-toughness correlations have been proposed to reflect the effect of crack-tip constraint on fracture-toughness. Test results from the uniaxial and biaxial tests were analyzed using the dual-parameter technology. Discrepancies between analysis results and cleavage initiation site data from fractographic examinations indicate that the analysis models are in need of further refinement. Addition of a precleavage, ductile-tearing element to the analysis model has the potential to resolve the noted discrepancies

  10. In situ biaxial rotation at low-temperatures in high magnetic fields

    International Nuclear Information System (INIS)

    We report the design, construction, and characterization of a biaxial sample rotation stage for use in a cryogenic system for orientation-dependent studies of anisotropic electronic transport phenomena at low temperatures and high magnetic fields. Our apparatus allows for continuous rotation of a sample about two axes, both independently and simultaneously

  11. 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.

  12. An empirical growth model for the biaxially aligned yttria stabilized zirconia films deposited by ion beam assisted deposition

    International Nuclear Information System (INIS)

    An empirical model is presented to describe the development of the biaxial alignment in ion beam assisted deposited (IBAD) yttria stabilized zirconia (YSZ) films. The model is based on Bradley's description for the orientation of grains on the surface of the IBAD YSZ film. The measured biaxial alignment of the grains on the surface of the YSZ film was plotted as a function of film thickness. The graph was fitted using the equation in our model and the parameters were calculated. We used these parameters to calculate the average biaxial alignment of the YSZ film as a function of thickness. The calculated results are close to the experimental results

  13. A k · p analytical model for valence band of biaxial strained Ge on (001) Si1?xGex

    International Nuclear Information System (INIS)

    In this paper, the dispersion relationship is derived by using the k · p method with the help of the perturbation theory, and we obtain the analytical expression in connection with the deformation potential. The calculation of the valence band of the biaxial strained Ge/(001)Si1?xGex is then performed. The results show that the first valence band edge moves up as Ge fraction x decreases, while the second valence band edge moves down. The band structures in the strained Ge/ (001)Si0.4Ge0.6 exhibit significant changes with x decreasing in the relaxed Ge along the [0, 0, k] and the [k, 0, 0] directions. Furthermore, we employ a pseudo-potential total energy package (CASTEP) approach to calculate the band structure with the Ge fraction ranging from x = 0.6 to 1. Our analytical results of the splitting energy accord with the CASTEP-extracted results. The quantitative results obtained in this work can provide some theoretical references to the understanding of the strained Ge materials and the conduction channel design related to stress and orientation in the strained Ge pMOSFET. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  14. Biaxial creep behavior of ribbed GCFR cladding at 6500C in nominally pure helium (99.99%)

    International Nuclear Information System (INIS)

    Biaxial creep-rupture tests were conducted on 12 prototypic GCFR fuel-cladding specimens at 6500C 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

  15. A novel indirect tensile test method to measure the biaxial tensile strength of concretes and other quasibrittle materials

    International Nuclear Information System (INIS)

    A novel indirect tensile test method, the biaxial flexure test (BFT) method, has been developed to measure the biaxial tensile strength of concretes. The classical modulus of rupture (MOR) test has been generalized to three dimensions. In this method, we use a circular plate as the new test specimen. This plate is supported by an annular ring. We apply an external load to this specimen through a circular edge. The centers of the specimen, the loading device and the support are identical. The biaxial tensile strength measured by this new method is about 19% greater than the uniaxial tensile strength obtained from the classical modulus of rupture test as reported by other researchers. However, at the same time, we also found that the stochastic deviation of the biaxial tensile strength is about 63% greater than the uniaxial strength

  16. 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)

  17. 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.

  18. Comparison of different modelling strategies for the representation of non linear response of RC columns subjected to biaxial loading

    OpenAIRE

    Rodrigues, H.; Varum, H.; Are?de, A.; Costa, A.

    2011-01-01

    Aiming at studying the performance of different non-linear modelling strategies for RC columns subjected to axial load and cyclic biaxial horizontal loading, several analyses were developed using the computer code SeismoStruct. This study comprised the simulation of 24 cantilever RC columns quasi-statically tested under constant axial force and cyclic uniaxial and biaxial displacements imposed with different loading paths. The results show that all adopted modelling strategies (distributed-in...

  19. The gravity dual of supersymmetric gauge theories on a biaxially squashed three-sphere

    International Nuclear Information System (INIS)

    We present the gravity dual to a class of three-dimensional N=2 supersymmetric gauge theories on a biaxially squashed three-sphere, with a non-trivial background gauge field. This is described by a 1/2 BPS Euclidean solution of four-dimensional N=2 gauged supergravity, consisting of a Taub–NUT–AdS metric with a non-trivial instanton for the graviphoton field. The holographic free energy of this solution agrees precisely with the large N limit of the free energy obtained from the localized partition function of a class of Chern–Simons quiver gauge theories. We also discuss a different supersymmetric solution, whose boundary is a biaxially squashed Lens space S3/Z2 with a topologically non-trivial background gauge field. This metric is of Eguchi–Hanson–AdS type, although it is not Einstein, and has a single unit of gauge field flux through the S2 cycle.

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

    International Nuclear Information System (INIS)

    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 ?/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. (condensed matter: structure, mechanical and thermal properties)

  1. Non-linear Response of Two-way Asymmetric Multistorey Building Under Biaxial Excitation

    Directory of Open Access Journals (Sweden)

    Nishant K. Kumar

    2013-04-01

    Full Text Available Seismic analysis is generally performed by creating a structural model which is excited with forces in two orthogonal directions separately i.e. they are subjected to uniaxial excitation. But an actual earthquake will have its effect in both the directions simultaneously. Limited research has been carried out on effect of such biaxial excitation. This paper deals with the non-linear performance of multi-storey buildings under biaxial excitation using various time-histories. The angle of incidence of earthquake forces will be varying between 0 to 360 degrees. Three building plans, with eccentricity along each of x and z directions in plan and a third with eccentricity in both the orthogonal direction, have been studied.Time history analysis has been carried out using SAP2000 after validating a preliminary model with experimental results available in reference literature.

  2. On the characterization of the plastic anisotropy in orthotropic sheet metals with a cruciform biaxial test

    International Nuclear Information System (INIS)

    A computational study was undertaken in order to identify the parameters of plastic constitutive models, generally used in numerical simulation of sheet metal forming. This study proposes a new methodology, based on the results of a single experimental biaxial test of a cruciform sample. Firstly, the geometry of the cruciform sample was optimized. Afterwards, finite element simulations were carried out for different combinations of material plastic properties that include a wide range of parameters commonly found in metallic sheets. Forward and reverse analysis algorithms were thus established; the forward algorithm allows the calculation of a unique response for a given set of plastic properties, whereas the reverse algorithm enables the extraction of plastic properties from a given set of data from the biaxial test on the cruciform specimen. The plastic behaviour of the material is described by the Hill'48 yield criterion and the isotropic hardening Swift law.

  3. Carrier transport simulation in a model liquid crystalline system with the biaxial Gay-Berne potential

    Science.gov (United States)

    Goto, Masanao; Takezoe, Hideo; Ishikawa, Ken

    2010-02-01

    In this paper, we performed carrier transport simulation to understand the unusual temperature dependence of the carrier mobility observed in nematic liquid crystals. For this purpose, we made a model liquid crystalline system consisting of biaxial Gay-Berne particles, and then we simulated hopping transport between these particles. The hopping rate was formulated suitably for the biaxial Gay-Berne particles based on the investigation of the electronic overlaps between actual aromatic molecules. The carrier transport simulation was performed by master equation method on the model system prepared by N-P-T ensemble Monte Carlo simulation. We reproduced gradual mobility increase in the nematic phase as a result of the change in the short range molecular order.

  4. An ultrafast image recovery and recognition system implemented with nanomagnets possessing biaxial magnetocrystalline anisotropy

    OpenAIRE

    D Souza, Noel; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2011-01-01

    A circular magnetic disk with biaxial magnetocrystalline anisotropy has four stable magnetization states which can be used to encode a pixel's shade in a black/gray/white image. By solving the Landau-Lifshitz- Gilbert equation, we show that if moderate noise deflects the magnetization slightly from a stable state, it always returns to the original state, thereby automatically de-noising the corrupted image. The same system can compare a noisy input image with a stored image ...

  5. 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...

  6. Determination of biaxial texture and intrinsic magnetic properties of hot rolled NdFeB samples

    International Nuclear Information System (INIS)

    Hot rolling of NdFeB ingots leads to magnets with a well developed biaxial texture. The texture and the intrinsic magnetic properties were determined by fitting of demagnetization curves. Using a Gaussian with an elliptical ansatz the resulting intrinsic properties are in agreement with data reported for Nd2Fe14B. The obtained texture parameters are comparable to those estimated from X-ray texture analysis using the component method. (orig.)

  7. The effect of glazing on the biaxial flexural strength of different zirconia core materials

    OpenAIRE

    Yener, E. S.; O?zcan, M.; Kazazog?lu, E.

    2011-01-01

    The aim of this study was to evaluate the effect of glazing on biaxial flexural strength of different zirconia core materials. Disc-shaped zirconia (ZirkonZahn, Cercon, Ceramill) specimens (15 mm x 1.15+/-0.02 mm) were prepared according to manufacturers' instructions. The specimens from each system were divided into 2 groups (N= 10): unglazed and glazed. Glaze liquid was applied on the entire surface of the specimens of the glazed group and fired according to manufacturers' instructions. Fle...

  8. 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-?m 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 ?c and was 47.3% for specimens with ?c = 40%. All specimens could be stretched until failure to rupture. The probability for crack initiation within the cylinder was ?c ?c >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.

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

    OpenAIRE

    Bandar Mohammed Abdullah Al-Makramani; Abdul Aziz Abdul Razak; Mohamed Ibrahim Abu-Hassan

    2010-01-01

    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 accordan...

  10. Dynamic fragmentation of a brittle plate under biaxial loading: strength or toughness controlled?

    OpenAIRE

    Levy, S.; Molinari, J. F.; Radovitzky, Raul

    2011-01-01

    The fragmentation of a brittle plate subjected to dynamic biaxial loading is investigated via numerical simulations. The aim is to extend our understanding of the dynamic processes affecting fragment size distributions. A scalable computational framework based on a hybrid cohesive zone model description of fracture and a discontinuous Galerkin formulation is employed. This enables large-scale simulations and, thus, the consideration of rich distributions of defects, as well as an accurate acc...

  11. Tresca criterion for plasticity and viscoplasticity: Application to localization in biaxial loading conditions

    OpenAIRE

    Bolis C.; Dequiedt J.L.; Dambakizi F.

    2012-01-01

    It has been proved that plastic instabilities in biaxial stretching conditions were better reproduced by using a Tresca yield surface rather than a Von Mises one. The simulation of the phenomenon in an expanding TA6V4 (Ti-6Al-4V alloy) shell experiment is performed using the Tresca criterion and both elasto-plastic and viscoplastic constitutive models: in this aim, Tresca flow surfaces had to be defined in viscoplasticity. The two models exhibit localization but, whereas the elastoplastic cas...

  12. Hot cell installation for biaxial creep and burst testing of cladding specimens

    International Nuclear Information System (INIS)

    The L.H.M.A. hot laboratory provides a range of facilities for the mechanical testing of cladding material from irradiated fuel pins. This paper gives a brief description of the apparatus for biaxial creep and burst testing that has been developed in the laboratory. This equipment is installed in a relatively small ?-?-? lead-shielded hot cell. Techniques for specimen preparation and conditioning as well as the test procedures are indicated. (author)

  13. Biaxially aligned YSZ and CeO2 buffer layers on hastelloy prepared by magnetron IBAD

    International Nuclear Information System (INIS)

    Full text: The development of high-current, flexible superconducting YBCO tapes is based on a metal substrates overcoated with a biaxially aligned oxide buffer layer to serve as a template for the epitaxial growth of c-axis oriented Yba2Cu3O7 thin films. A secondary function of the buffer is to act as a diffusion barrier to metal species to prevent them from poisoning the superconducting film. Widely studied oxide buffer layers include yttria-stabilised zirconia (YSZ) and cerium oxide (CeO2) produced by ion-beam-assisted deposition (IBAD). We have combined IBAD with magnetron sputtering to deposit biaxially aligned YSZ and CeO2 on Hastelloy C276 substrates held at room temperature. The ion beam is directed at 55deg to the normal of the film plane. In addition, we achieved room temperature epitaxial growth of CeO2 films on IBAD YSZ films by bias sputtering to form biaxially aligned CeO2/YSZ bilayers. The crystalline quality and inplane orientation of the films (200 nm thick) were investigated by x-ray diffraction techniques including ? and ? scans and pole figures. The IBAD YSZ and CeO2 films have a (111) pole in the ion beam direction with a full width at half maximum, FWHM = 24 - 30 deg; the CeO2/YSZ bilayer is similarly aligned with FWHM = 32 deg

  14. Uniaxial and biaxial tensioning effects on thin membrane materials. [large space structures

    Science.gov (United States)

    Hinson, W. F.; Goslee, J. W.

    1980-01-01

    Thin laminated membranes are being considered for various surface applications on future large space structural systems. Some of the thin membranes would be stretched across or between structural members with the requirement that the membrane be maintained within specified limits of smoothness which would be dictated by the particular applications such as antenna reflector requirements. The multiaxial tensile force required to maintain the smoothness in the membrane needs to be determined for use in the structure design. Therefore, several types of thicknesses of thin membrane materials have been subjected to varied levels of uniaxial and biaxial tensile loads. During the biaxial tests, deviations of the material surface smoothness were measured by a noncontacting capacitance probe. Basic materials consisted of composites of vacuum deposited aluminum on Mylar and Kapton ranging in thickness from 0.00025 in (0.000635 cm) to 0.002 in (0.00508 cm). Some of the material was reinforced with Kevlar and Nomex scrim. The uniaxial tests determined the material elongation and tensile forces up to ultimate conditions. Biaxial tests indicated that a relatively smooth material surface could be achieved with tensile force of approximately 1 to 15 Newtons per centimeter, depending upon the material thickness and/or reinforcement.

  15. YSZ buffer layers and YBCO superconducting tapes with enhanced biaxial alignment and properties

    International Nuclear Information System (INIS)

    Commercial applications of YBa2Cu3O7 (YBCO) superconducting cables require viable and scalable manufacturing processes. We have investigated the evolution of the biaxial alignment of yttria-stabilized zirconia (YSZ) buffer layers with increasing film thickness (50-900 nm) and report on a method of fabricating highly aligned YBCO tapes using a thin epitaxial YSZ buffer layer as template. The method employs magnetron and ion beam assisted deposition (IBAD) techniques followed by epitaxial growth to produce the buffer architectures IBAD-YSZ and epi-YSZ/IBAD-YSZ onto optically polished hastelloy metal substrates. Subsequent in situ deposition of YBCO films is used to determine the biaxial alignment at the surface of the buffer architecture, and to show that 100-200 nm thick epi-YSZ layers suffice to yield YBCO tapes that have enhanced biaxial alignment (?phi=9-10 deg. ) and high critical current densities: Jc(77 K)=(1-2)x106 A cm-2 and Jc(5 K,1 T)=8x106 A cm-2. Atomic force microscopy of the surface microstructure of the YSZ buffer layers and YBCO films reveals some grain coarsening in the epi-YSZ layers compared to the IBAD-YSZ layers while the YBCO tapes show significant outgrowths (?200 nm) and large grains (800-1200 nm) that are similar to high-Jc YBCO films grown on single crystal MgO(1 0 0) substrates

  16. Experimental Observations of Quasi-Static-Dynamic Formability in Biaxially Strained AA5052-O

    Science.gov (United States)

    Liu, Dahai; Yu, Haiping; Li, Chunfeng

    2011-03-01

    To establish the efficacy of electromagnetically assisted sheet metal stamping (EMAS), a series of combined hydraulic bulging and electromagnetic forming (EMF) experiments are presented to evaluate the biaxial quasi-static-dynamic formability of an aluminum alloy (AA5052-O) sheet material. Data on formability are plotted in principal strain space and show an enhanced biaxial formability beyond the corresponding experimental results from conventional forming limit diagram. The plastic strains produced by the combined process are a little larger than or at least similar with those obtained in the fully dynamic EMF process. In addition, the biaxial forming limits of aluminum sheets undergoing both very low and high quasi-static prestraining are almost similar in quasi-static-dynamic bulging process. Limit formability seems to depend largely on the high-velocity loading condition as dictated by EMF. It appears that in quasi-static-dynamic forming, quasi-static loading is not of primary importance to the material's formability. Based on these observations, one may be able to develop forming operations that take advantage of this formability improvement of quasi-static-dynamic deformation. Also, this could enable the use of a quasi-static preform fairly close to the quasi-static material limits for the design of an EMAS process.

  17. Spin-orbit interactions of a Gaussian light propagating in biaxial crystals.

    Science.gov (United States)

    Lu, Xiancong; Chen, Lixiang

    2012-05-21

    Based on the plane-wave angular spectrum representation, we derive a formal expression for any light fields propagating in biaxial crystals, and particularly, present an effective numerical method to investigate the propagation behavior for a Gaussian light beam. Unlike uniaxial crystals, we observe the intriguing formation, repulsion and disappearance of vortex pairs, as the refractive indices deviate slightly and gradually from the uniaxial limit. In the Minkowski angular momentum picture, we also investigate the orbital angular momentum dynamics for both left- and right-handed circularly polarized components. Of further interest is the revelation of nonconservation of the angular momentum within the light field during the spin-orbit interactions, and the optical torque per photon that the light exerts on the biaxial crystal is quantified. We interpret these interesting phenomena by the weakly broken rotational invariance of biaxial crystals. The self-consistency of our theory is confirmed by the balance equation describing the conservation law of total angular momentum of filed and crystal in the Minkowski picture. PMID:22714163

  18. Mean-field and computer simulation study of a biaxial nematogenic lattice model mimicking shape amphiphilicity

    International Nuclear Information System (INIS)

    The present Letter considers a biaxial nematogenic lattice model, involving particles of D2h symmetry, whose centres of mass are associated with a 3-dimensional simple-cubic lattice; the pair potential is isotropic in orientation space, and restricted to nearest neighbours.Let the two orthonormal triads {uj,j=1,2,3} and {vk,k=1,2,3} define orientations of a pair of interacting particles, and let Gjk=P2(vj-bar uk), where P2(...) denotes the second Legendre polynomial. By now, interaction models defined by suitable linear combinations of terms Gjk have been studied for some time in the literature; a new and simplified form for them has recently been proposed by Sonnet, Virga and Durand [Phys. Rev. E 67 (2003) 061701]; the present potential follows their idea, but now uses different parameter values (pushing, so to speak, their simplification even further), i.e., it has an extreme biaxial mesogenic form which, by elementary geometrical identities, can be written in two equivalent ways ?=?[-(G11+G22)+(G12+G21)]=?[-2(G11+G22)+G33], where ? denotes a positive quantity setting energy and temperature scales (i.e., T*=kBT/?).A mean-field analysis predicts the existence of a direct second-order transition between biaxial and isotropic phases; Monte Carlo simulations qualitatively confirm the prediction.Some thirty years ago, Alben [J. Chem. Phys. 59 (1973) 4299] suggested the possibility of producing biaxial nematic order by mixing rod-like and disc-like (mesogenic) moleculike and disc-like (mesogenic) molecules; the idea was investigated theoretically in a number of cases, but so far no experimental realisation has been observed. On the other hand, 'shape amphiphlic' mesogens, containing both rod-like and disc-like parts covalently bonded together, have been synthesised in the last few years, although thermotropic biaxial nematic behaviour has not been experimentally detected in these pure compounds either. The present interaction model can be seen as a simple and extreme approximation to such a behaviour, favouring parallel orientation of rod moieties, parallel orientation of disc moieties, and mutual perpendicular orientations between rods and discs

  19. Influence of a multiaxial stress on the reversible and irreversible magnetic behaviour of a 3%Si-Fe alloy

    OpenAIRE

    Rekik, Mahmoud; Hubert, Olivier; Daniel, Laurent

    2014-01-01

    The research presented in this paper is motivated by the design of electrical devices submitted to mechanical stress. It aims at studying the magnetic behaviour of ferromagnetic materials submitted to biaxial stress. It deals with the evolution of the magnetic susceptibility, coercive field and magnetic losses with respect to stress, magnetic field level and frequency. These quantities are of primary importance in the design of rotors for high speed rotating machines. The work is focused on t...

  20. High-resolution calorimetric study of a liquid crystalline organo-siloxane tetrapode with a biaxial nematic phase.

    Science.gov (United States)

    Cordoyiannis, George; Apreutesei, Daniela; Mehl, Georg H; Glorieux, Christ; Thoen, Jan

    2008-07-01

    High-resolution adiabatic scanning calorimetry and differential scanning calorimetry have been employed to study the thermal behavior of an organo-siloxane tetrapode reported to exhibit a biaxial nematic phase. No signature of the uniaxial to biaxial nematic phase transition could be retraced in sequential heating and cooling runs under different scanning rates, within the experimental resolution. The results obtained reveal that an extremely small heat should be involved in the uniaxial to biaxial nematic phase transition. The isotropic to uniaxial nematic transition at 318+/-0.01 K is very stable, and it is weakly first order with a rather small latent heat of 0.20+/-0.02 J/g . PMID:18763974

  1. A Nanomembrane-Based Bandgap-Tunable Germanium Microdisk Using Lithographically-Customizable Biaxial Strain for Silicon-Compatible Optoelectronics

    CERN Document Server

    Sukhdeo, David S; Kang, Ju-Hyung; Brongersma, Mark L; Saraswat, Krishna C

    2014-01-01

    Strain engineering has proven to be vital for germanium-based photonics, in particular light emission. However, applying a large permanent biaxial strain to germanium has been a challenge. We present a simple, CMOS-compatible technique to conveniently induce a large, spatially homogenous strain in microdisks patterned within ultrathin germanium nanomembranes. Our technique works by concentrating and amplifying a pre-existing small strain into the microdisk region. Biaxial strains as large as 1.11% are observed by Raman spectroscopy and are further confirmed by photoluminescence measurements, which show enhanced and redshifted light emission from the strained microdisks. Our technique allows the amount of biaxial strain to be customized lithographically, allowing the bandgaps of different microdisks to be independently tuned in a single mask process. Our theoretical calculations show that this platform can deliver substantial performance improvements, including a >200x reduction in the lasing threshold, to bia...

  2. The characteristics of high-temperature biaxial fatigue strength in type 304 stainless steel for FBR high-temperature structure

    International Nuclear Information System (INIS)

    As alink the chain of 'Study for practical use of Tank Type FBR', 'Practical use of inelastic analysis method to FBR structural design' has been carriedoutas a cooperative study for three yearssince 1984. In the cooperative study, the investigation such as high-temperature deformation behavior and high-temperature fatigue life characteristics of structure materiols is one of the most important problems. In CRIEPI, in order to investigate fatigue life characteristics of reactor vessel material subjected to cyclic thermalstress, biaxial fatigue lif characteristics evaluation for SVS304 steel is conducted. We conduct teusion compression-tortion tests at 550 deg C that have phase angle 90 deg between axial strainand tortional strain. This report show result of study for biaxial fatigue life evaluation method. We find that high temperature low cycle biaxial fatigue life, not oulyin-phasebut also out-of-phase, have good relation to equivalent shear strain range. (author)

  3. 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.

  4. Effect of Temperature and Mechanical Stress on Barrier Properties of Polymeric Films Used for Food Packaging

    OpenAIRE

    Mrkic?, Sas?a; Galic?, Kata; Ivankovic?, Marica

    2007-01-01

    Abstract The permeance of carbon dioxide, oxygen, nitrogen, and air through commercial polymers based on polyethylene (PE), biaxially oriented polypropylene (BOPP), and polyamide (PA) used for food packaging is reported. The influence of temperature (from 10 to 60°C) and crease stress cycles (30, 50, 70, and 110) on gas permeance is also analyzed. Generally, the highest changes in gas permeance changes with increased stress cycles are observed with films having a metallized layer ...

  5. Fatigue Assessment of Components Subjected to Non-Proportional Stress Histories

    OpenAIRE

    Bruun, Oyvind Aleksander

    2013-01-01

    The fatigue assessment of components subjected to complex loading histories is a challenging topic. Several criteria intended for use under multiaxial stress-states and non-proportional loading have been proposed by many researchers throughout the years. This thesis is intended as a critical review of the fatigue assessment of both proportional and non-proportional stress histories. A database consisting of 268 experimental tests for biaxial fatigue limits were collected from various sources....

  6. Role of stresses in annealing of ion-implantation damage in Si

    International Nuclear Information System (INIS)

    Recent results showing a crystallographic orientation dependence of growth kinetics, secondary defects, and stress relief in annealing of ion-implanted Si are shown to be self-consistent if interpreted in terms of the influence of stresses upon annealing processes. The stress influence proposed is microplastic shear which is induced in [112] directions on (111) planes inclined to the implant surface by the biaxial stress created in the implant region by ion-implantation damage. The shear stresses are shown to be dependent on crystallographic orientation in a manner consistent with the model

  7. Mechanical behavior of fetal dura mater under large deformation biaxial tension.

    Science.gov (United States)

    Bylski, D I; Kriewall, T J; Akkas, N; Melvin, J W

    1986-01-01

    The mechanical behavior of fetal dura mater was investigated by means of a biaxial tension test designed to simulate the constraints imposed on the membrane by the cranial bones. The experimental results are compared with the theoretical results obtained by using two published strain energy functions: one defined by Mooney and Rivlin (MR) and the other by Skalak, Tozeren, Zarda and Chien (STZC). The latter constitutive relations fit the experimental results consistently well. The STZC stiffness values from this series of tests are compared with those from membrane inflation tests performed previously and reported elsewhere by the authors. PMID:3949813

  8. Effect of an electric field on the bifurcation of a biaxially stretched incompressible slab rubber.

    Science.gov (United States)

    Díaz-Calleja, R; Sanchis, M J; Riande, E

    2009-12-01

    This paper describes the effect of an electrical field on the bifurcation phenomenon that appears in a biaxially stretched slab of Mooney-Rivlin material (M. Mooney, J. Appl. Phys. 11, 582 (1940)) subjected to equal dead loads. The main conclusion of the analysis is that the stretch ratio at which the bifurcation phenomenon appears crucially depends on the configuration of the system rubber slab-electrodes. The theoretical foundations of the present study are based on a recent formulation on this subject carried out by Dorfmann and Ogden (A. Dorfmann, R.W. Ogden, Acta Mech. 174, 167 (2005); J. Elasticity 82, 99 (2006)). PMID:20013020

  9. Directionally controlled superconductivity in ferromagnet/superconductor/ ferromagnet trilayers with biaxial easy axes

    OpenAIRE

    Visani, C.; Nemes, N. M.; Rocci, M.; Garci?a-herna?ndez, M.; Santamari?a, J.

    2010-01-01

    We report on the magnetic anisotropy controlled modulation of the superconductivity in La0.7 Ca0.3 MnO3/ YBa 2 Cu3O7-? / La0.7 Ca 0.3 MnO3 ferromagnet/superconductor/ferromagnet hybrids with biaxial easy axes. The magnetoresistance (MR) is determined by the local misalignment of the magnetizations in the two layers and exhibits a positive MR plateau for antiparallel alignment along the easy axes and negative MR peaks at the coercive field near the hard axes. This evidences the importance of ...

  10. Effects of biaxial strains on the magnetic properties of Co-graphene heterojunctions

    Science.gov (United States)

    Lee, Sangho; Choi, Heechae; Chung, Yong-Chae

    2012-06-01

    Using the ab initio calculations, the changes of the magnetic properties of Co atoms on graphene for biaxial strains on graphene were investigated. Our calculation results showed that the compression of graphene changed the magnetic moments of Co adatoms more significantly than the elongation of graphene. From the 3d-electron density of states of Co atoms, the changes of magnetic properties of Co atoms on graphene were found to result from the significant hybridization between Co 3dyz and C 2pz orbitals. It was demonstrated that this 3d-electron hybridization of Co/graphene system originated from the strain-induced change of the local atomic structure.

  11. Nematic-Wetted Colloids in the Isotropic Phase Pairwise Interaction, Biaxiality and Defects

    CERN Document Server

    Galatola, P

    2001-01-01

    We calculate the interaction between two spherical colloidal particles embedded in the isotropic phase of a nematogenic liquid. The surface of the particles induces wetting nematic coronas that mediate an elastic interaction. In the weak wetting regime, we obtain exact results for the interaction energy and the texture, showing that defects and biaxiality arise, although they are not topologically required. We evidence rich behaviors, including the possibility of reversible colloidal aggregation and dispersion. Complex anisotropic self-assembled phases might be formed in dense suspensions.

  12. Particle flow of ceramic breeder pebble beds in bi-axial compression experiments

    International Nuclear Information System (INIS)

    Pebble beds of ceramic material are investigated within the framework of developing solid breeder blankets for future fusion power plants. A thermo-mechanical characterisation of such pebble beds is mandatory for understanding the behaviour of pebble beds, and thus the overall blanket, under fusion environment conditions. The mechanical behaviour of pebble beds is typically explored with uni-axial, bi-axial and tri-axial compression experiments. The latter two types of experiment are particularly revealing since they contain explicitly, beyond a compression behaviour of the bed, information on the conditions for pebble flow, i.e. macroscopic relocation, in the pebble bed. (orig.)

  13. Non-Kramers degeneracy and oscillatory tunnel splittings in the biaxial spin system

    International Nuclear Information System (INIS)

    We have investigated analytically quantum tunnelling of large spin in the biaxial spin system with the magnetic field applied along the hard and medium anisotropy axes by using Schroedinger's interpretation of quantum mechanics. When the magnetic field parallels the hard axis, the tunnel splittings of all the energy level pairs become oscillatory as a function of the magnetic field. The quenching points are completely determined by the coexistence of solutions of Ince's equation. When the magnetic field points to the medium axis, the tunnel splitting oscillations disappear due to the absence of coexistence of solutions. These results coincide with the recent experimental observations in the nanomagnet Fe8. (author)

  14. Plasma Surface Functionalization of Biaxially Oriented Polypropylene Films with Trimethyl Borate

    OpenAIRE

    Nursel Dilsiz; Hande Yavuz; Süleyman Çörekçi; Mehmet Çakmak

    2011-01-01

    The radiofrequency plasma (13.56 MHz) was employed to polymerize trimethyl borate (TMB) monomer/N2 gas mixture on the surface of biaxially oriented polypropylene (BOPP) films. Plasma polymer coated polypropylene films were examined by flame retardancy test (limiting oxygen index, LOI). The highest LOI value calculated for the untreated BOPP sample was 18.4 (v/v O2%) and 24.2 (v/v O2%) for the 55 W 30 minutes treated sample. The plasma polymers were characterized by FTIR spectroscopy and AFM. ...

  15. SPICE compatible analytical electron mobility model for biaxial strained-Si-MOSFETs

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhry, Amit; Sangwan, S. [UIET, Panjab University, Chandigarh (India); Roy, J. N., E-mail: amit_chaudhry01@yahoo.com [Solar Semiconductro Pvt. Ltd, Hyderabad (India)

    2011-05-15

    This paper describes an analytical model for bulk electron mobility in strained-Si layers as a function of strain. Phonon scattering, columbic scattering and surface roughness scattering are included to analyze the full mobility model. Analytical explicit calculations of all of the parameters to accurately estimate the electron mobility have been made. The results predict an increase in the electron mobility with the application of biaxial strain as also predicted from the basic theory of strain physics of metal oxide semiconductor (MOS) devices. The results have also been compared with numerically reported results and show good agreement. (semiconductor devices)

  16. SPICE compatible analytical electron mobility model for biaxial strained-Si-MOSFETs

    Science.gov (United States)

    Chaudhry, Amit; Roy, J. N.; Sangwan, S.

    2011-05-01

    This paper describes an analytical model for bulk electron mobility in strained-Si layers as a function of strain. Phonon scattering, columbic scattering and surface roughness scattering are included to analyze the full mobility model. Analytical explicit calculations of all of the parameters to accurately estimate the electron mobility have been made. The results predict an increase in the electron mobility with the application of biaxial strain as also predicted from the basic theory of strain physics of metal oxide semiconductor (MOS) devices. The results have also been compared with numerically reported results and show good agreement.

  17. 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

  18. Development of serial measurement system for three-dimensional stress determination by over-coring the strains on borehole wall

    International Nuclear Information System (INIS)

    In order to determine the three-dimensional stress state in serial order, the authors developed the serial measurement system for three-dimensional stress determination by over-coring the strains on the borehole wall. The serial stress measurements give the value of the stresses with high accuracy and bring the regional stress variations. In this paper, the authors describe the studies through FEM analysis on the effect of over-coring diameter, the influence of strain gauge length and the behavior of strain on the borehole wall, induced by biaxial external loading. We developed the multi-strain gauge mounted packer and examined it by measuring the strains on the borehole wall through biaxial loading test. The Laboratory tests showed its applicability to practical use. (author)

  19. 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 ? 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.

  20. Electronic band structure calculations for biaxially strained Si, Ge, and III-V semiconductors

    Science.gov (United States)

    Kim, Jiseok; Fischetti, Massimo V.

    2010-07-01

    Electronic band structure and effective masses for relaxed and biaxially strained Si, Ge, III-V compound semiconductors (GaAs, GaSb, InAs, InSb, InP) and their alloys (InxGa1-xAs, InxGa1-xSb) on different interface orientations, (001), (110), and (111), are calculated using nonlocal empirical pseudopotential with spin-orbit interaction. Local and nonlocal pseudopotential parameters are obtained by fitting transport-relevant quantities, such as band gap and deformation potentials, to available experimental data. A cubic-spline interpolation is used to extend local form factors to arbitrary q and to obtain correct workfunctions. The nonlocal and spin-orbit terms are linearly interpolated between anions and cations for III-V semiconductors. The virtual crystal approximation is employed for the InxGa1-xAs and InxGa1-xSb alloys and deformation potentials are determined using linear deformation-potential theory. Band gap bowing parameters are extracted using least-square fitting for relaxed alloys and for strained InxGa1-xAs on (001), (110), and (111) InP. The dependence on biaxial strain of the electron and hole effective masses at the symmetry points ?, X, and L exhibits a continuous variation at ? and L but sudden changes appear at ? minima caused by the flatness of the dispersion along the ? line near the minimum.

  1. Band gap engineering of FeS2 under biaxial strain: a first principles study.

    Science.gov (United States)

    Xiao, Pin; Fan, Xiao-Li; Liu, Li-Min; Lau, Woon-Ming

    2014-11-28

    The promising photovoltaic activity of pyrite (FeS2) is attributed to its excellent optical absorptivity and earth abundance, but its band gap, 0.95 eV, is slightly lower than the optimum value of 1.3 eV. Here we report the first investigation of strained FeS2, whose band gap can be increased by ?0.3 eV. The influence of uniaxial and biaxial strains on the atomic structure as well as the electronic and optical properties of bulk FeS2 is systematically examined by the first principles calculations. We found that the biaxial strain can effectively increase the band gap with respect to uniaxial strain. Our results indicate that the band gap increases with increasing tensile strain to its maximum value at 6% strain, but under the increasing compressive strain, the band gap decreases almost linearly. Moreover, the low intensity states at the bottom of the conduction band disappear and a sharp increase in the intensity appears at the lower energy level under the tensile strain, which causes the red shift of the absorption edge and enhances the overall optical absorption. With the increase of the band gap and enhanced optical absorption, FeS2 will make a better photovoltaic material. PMID:25308322

  2. Novel properties of wave propagation in biaxially anisotropic left-handed materials

    CERN Document Server

    Shen, J Q

    2003-01-01

    Some physically interesting properties and effects of wave propagation in biaxially anisotropic left-handed materials are investigated in this paper. We show that in the biaxially gyrotropic left-handed material, the left-right coupling of circularly polarized light arises due to the negative indices in permittivity and permeability tensors of gyrotropic media. It is well known that the geometric phases of photons inside a curved fiber in previous experiments often depend on the cone angles of solid angles subtended by a curve traced by the direction of wave vector of light, at the center of photon momentum space. Here, however, for the light propagating inside certain anisotropic left-handed media we will present a different geometric phase that is independent of the cone angles. The extra phases of electromagnetic wave resulting from the instantaneous helicity inversion at the interfaces between left- and right- handed (LRH) media is also studied in detail by using the Lewis-Riesenfeld invariant theory. Som...

  3. 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.

  4. 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.

  5. Method of depositing a protective layer over a biaxially textured alloy substrate and composition therefrom

    Science.gov (United States)

    Goyal, Amit (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Paranthaman, Mariappan (Knoxville, TN); Lee, Dominic F. (Knoxville, TN); Feenstra, Roeland (Knoxville, TN); Norton, David P. (Gainesville, FL)

    2002-01-01

    A laminate article consists of a substrate and a biaxially textured protective layer over the substrate. The substrate can be biaxially textured and also have reduced magnetism over the magnetism of Ni. The substrate can be selected from the group consisting of nickel, copper, iron, aluminum, silver and alloys containing any of the foregoing. The protective layer can be selected from the group consisting of gold, silver, platinum, palladium, and nickel and alloys containing any of the foregoing. The protective layer is also non-oxidizable under conditions employed to deposit a desired, subsequent oxide buffer layer. Layers of YBCO, CeO.sub.2, YSZ, LaAlO.sub.3, SrTiO.sub.3, Y.sub.2 O.sub.3, RE.sub.2 O.sub.3, SrRuO.sub.3, LaNiO.sub.3 and La.sub.2 ZrO.sub.3 can be deposited over the protective layer. A method of forming the laminate article is also disclosed.

  6. Specimen Designs for Testing Advanced Aeropropulsion Materials Under In-Plane Biaxial Loading

    Science.gov (United States)

    Ellis, John R.; Abul-Aziz, Ali

    2003-01-01

    A design study was undertaken to develop specimen designs for testing advanced aeropropulsion materials under in-plane biaxial loading. The focus of initial work was on developing a specimen design suitable for deformation and strength tests to be conducted under monotonic loading. The type of loading initially assumed in this study was the special case of equibiaxial, tensile loading. A specimen design was successfully developed after a lengthy design and optimization process with overall dimensions of 12 by 12 by 0.625 in., and a gage area of 3.875 by 3.875 by 0.080 in. Subsequently, the scope of the work was extended to include the development of a second design tailored for tests involving cyclic loading. A specimen design suitably tailored to meet these requirements was successfully developed with overall dimensions of 12 by 12 by 0.500 in. and a gage area of 2.375 by 2.375 by 0.050 in. Finally, an investigation was made to determine whether the specimen designs developed in this study for equibiaxial, tensile loading could be used without modification to investigate general forms of biaxial loading. For best results, it was concluded that specimen designs need to be optimized and tailored to meet the specific loading requirements of individual research programs.

  7. Biaxial Texture Evolution of Nanostructured Films under Dynamic Shadowing Effect and Applications

    Science.gov (United States)

    Chen, Liang

    Texture formation and evolution in polycrystalline films are quite complicated, and they still remain as challenging subjects. Oblique angle deposition is an effective way to control the texture due to the shadowing effect introduced by oblique incident flux. A new dynamic oblique angle sputter deposition technique, called flipping rotation, was developed. In this rotation mode, the substrate is arranged to rotate continuously at a fixed speed around an axis lying within and parallel to the substrate. The incident flux is always perpendicular to the rotational axis and the flux incident angle relative to the substrate normal changes continuously. To study the texture formation and evolution of Mo and W films grown by DC magnetron sputter depositions, three film categories were prepared: (1) normal incidence deposition without the shadowing effect, (2) stationary oblique angle deposition at various fixed flux incident angles with static shadowing effect, and (3) convention rotation and flipping rotation deposition with dynamic shadowing effect. Under the normal incidence deposition, ultrathin (2.5 nm) to thin (100 nm) Mo films have been deposited on SO2 membranes on transmission electron microscopy (TEM) grids. These samples can be directly compared with the films grown on glass or native oxide covered Si substrates. The result of a fiber texture with the [110] out-of-plane direction implies that the growth has gone through a recrystallization process that selects the minimum surface energy plane parallel to the substrate. This is in contrast to the conventional understanding of the selection of out-of-plane orientation, which is the fastest growth direction [100] at room temperature based on the low Mo homologous temperature (room temperature/melting temperature) of ~0.1. Under stationary oblique angle deposition, Mo thin films in the range of 175 nm to 1300 nm were observed to undergo a dramatic change in crystal texture orientation from a (110)[11¯¯0] biaxial texture that has the minimum energy plane (110) parallel to the substrate surface at low oblique angle deposition (0biaxial texture at high oblique angle deposition (??60°) due to the large tilting of the fastest growth [001] direction towards the flux. We believe that the biaxial textures formation under different flux incident angles have different out-of-plane orientation selection mechanisms, i.e., minimum surface energy plane vs. fastest growth direction. However, the in-plane orientation selection could still be explained by the largest capture area model where the in-plane texture favors the orientations along the largest capture area or length facing the flux. Under dynamic shadowing effect using the newly developed dynamic flipping rotation of the substrate, both Mo and W thin films in the range of 550 nm to 650 nm grown on amorphous substrates have (110)[11¯0] biaxial textures with a body center cubic (BCC) structure characterized by a reflection high-energy electron diffraction pole figure technique developed in house. Depending on the rotational speed in the flipping rotation, the biaxial textures can have various morphologies, such as vertical, S-shape, or C-shape nanocolumns, as observed by scanning electron microscopy. The possible growth mechanisms in the formation of various morphologies due to different degrees of shadowing effect were suggested. This is in contrast with the films grown by conventional rotation, which usually have fiber textures with different out-of-plane orientation, [111] for Mo, or even a different phase, A15 for W. The biaxial Mo(110) and W(110) thin films were used as buffer layers to grow semiconductor films of GaN for the LED applications and CdTe for the thin film photovoltaic applications. Detailed X-ray pole figure analyses show the heteroepitaxial growth of GaN/Mo, GaN/W, and CdTe/Mo. A prototype biaxial CdTe film based Schottky junction solar cell on biaxial Mo film has been fabricated and characterized. Although the open circuit voltage is small for the prototype device, th

  8. On the sensitivity of directions that support Voigt wave propagation in infiltrated biaxial dielectric materialsfn" rid="fn1"/>

    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.

  9. 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.

  10. Localized surface plasmon resonance anisotropy in template aligned silver nanoparticles: A case of biaxial metal optics

    Science.gov (United States)

    Ranjan, Mukesh; Bhatnagar, Mukul; Mukherjee, Subroto

    2015-03-01

    Generalized ellipsometry is used to extract the dielectric functions of self-aligned silver nanoparticles on silicon ripple patterns which account for the anisotropic Localized Surface Plasmon Resonance shown by such nanostructures. The biaxial nature of dielectric functions shows its presence through the modified in-plane plasmonic behaviour as compared to the case of random nanoparticles. The nature of in-plane optical coupling and out of plane metallic behavior is further investigated by tuning the interparticle gap along the ripple direction and also varying the ripple periodicity. Thus, we propose that generalized ellipsometry may be used as an effective process monitoring technique to develop anisotropic plasmonic substrates with potential applications in photovoltaic systems as a plasmonic back reflector.

  11. DIC-aided biaxial fatigue tests of a 304L steel

    Directory of Open Access Journals (Sweden)

    Le-Roux J.C.

    2010-06-01

    Full Text Available Several biaxial fatigue tests are conducted up to 106 cycles at room temperature in the context of a collaboration LMT-Cachan / EDF / AREVA / SNECMA / CEA. Malteses cross specimens of 304L steel, designed to initiate crack in the bulk, are loaded by a triaxial testing machine. A Digital Image Correlation technique is used to measure strain during loading and detect crack initiation early. A special optical assembly and a stroboscopic sampling method are set up in this purpose. Several types of loadings are performed: equibiaxial with a loading ratio R = 0.1, equibiaxial with loading ratio R = –1, pseudo uniaxial (cyclic loading at R= 0.1 in one direction and constant loading in the other. First results are commented.

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

    Scientific Electronic Library Online (English)

    Belinda, Pingguan-Murphy; Illida, Nawi.

    2012-08-01

    Full Text Available SciELO Brazil | Language: English Abstract in english 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 glycosami [...] noglycans 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

  13. Molecular dynamics study on the equal biaxial tension of Cu/Ag bilayer films

    International Nuclear Information System (INIS)

    The mechanical behavior, dislocation nucleation and development, and the evolution of interface in Cu/Ag bilayer films during an equal biaxial tension were studied using molecular dynamics simulations. The results show that dislocations are prone to nucleate at the interface of Cu/Ag bilayer film, and then propagate toward the free surface. The deformation defects consist of partial dislocations and intrinsic stacking faults, accompanying with some extrinsic stacking faults and stacking fault tetrahedra which just occur at the interface and propagate in the Cu layer. Compared with Cu and Ag films, Cu/Ag bilayer films have the maximal yield strain. The surface roughness reaches maximum at the yield strain, and then rapidly decreases with the increase of strain. Atoms in stacking faults increase with the strain at the high strain rate, while the rule is reversed at the low strain rate.

  14. Biaxial wall element tests of reinforced and prestressed concrete containments with inward radial load on penetrations

    International Nuclear Information System (INIS)

    This work indicates that under internal overpressurization or other accident conditions, highly localized strains in the steel liner plate can result in liner tearing and subsequent containment leakage. In the prestressed concrete design, liner plate cracks occurred at the ends of anchorage angles. Inward movement of the penetration caused the liner plate to try to tear the anchorage from the concrete. Maximum liner distortion occurred at the junction of the liner with the ends of the anchorage angles. In the reinforced concrete design, the liner plate did not crack as a result of biaxial and inward load on the penetration. Dimples formed in the liner at multiple locations where studs anchored the liner to the concrete. (orig./HP)

  15. Tresca criterion for plasticity and viscoplasticity: Application to localization in biaxial loading conditions

    Science.gov (United States)

    Dequiedt, J. L.; Bolis, C.; Dambakizi, F.

    2012-08-01

    It has been proved that plastic instabilities in biaxial stretching conditions were better reproduced by using a Tresca yield surface rather than a Von Mises one. The simulation of the phenomenon in an expanding TA6V4 (Ti-6Al-4V alloy) shell experiment is performed using the Tresca criterion and both elasto-plastic and viscoplastic constitutive models: in this aim, Tresca flow surfaces had to be defined in viscoplasticity. The two models exhibit localization but, whereas the elastoplastic case develops shear banding in times in agreement with the onset of instabilities in the experiment, the viscoplastic case develops diffuse necking at later times. On the contrary, the viscoplastic simulation exhibits patterns the size of which seems in better agreement with the experimental ones.

  16. Tresca criterion for plasticity and viscoplasticity: Application to localization in biaxial loading conditions

    Directory of Open Access Journals (Sweden)

    Bolis C.

    2012-08-01

    Full Text Available It has been proved that plastic instabilities in biaxial stretching conditions were better reproduced by using a Tresca yield surface rather than a Von Mises one. The simulation of the phenomenon in an expanding TA6V4 (Ti-6Al-4V alloy shell experiment is performed using the Tresca criterion and both elasto-plastic and viscoplastic constitutive models: in this aim, Tresca flow surfaces had to be defined in viscoplasticity. The two models exhibit localization but, whereas the elastoplastic case develops shear banding in times in agreement with the onset of instabilities in the experiment, the viscoplastic case develops diffuse necking at later times. On the contrary, the viscoplastic simulation exhibits patterns the size of which seems in better agreement with the experimental ones.

  17. Measurement of texture in magnetic recording media using a biaxial vibrating sample magnetometer

    Science.gov (United States)

    Schmidlin, F.; Bissell, P. R.; Gotaas, J. A.

    1996-04-01

    A method is described for the determination of the three dimensional easy axis distribution in recording media using a biaxial vibrating sample magnetometer and compensation for out-of-plane demagnetization field effects. Comparison of Lorentzian function fits to the data and measurement of orientation ratio with theoretical calculations indicates that the method gives a reasonable measure of the easy axis distribution. Examination of the theoretical relationship indicates that low values of orientation ratio are insensitive to distribution width indicating that it is necessary to make a full measure of easy axis distribution in-plane. However, out-of-plane distributions are generally narrower and it is often possible to estimate distribution width from a simple orientation ratio measurement.

  18. Low-kappa' dielectric properties of UV-treated bi-axially oriented polypropylene films

    Energy Technology Data Exchange (ETDEWEB)

    Dervos, C T; Tarantili, P A; Athanassopoulou, M D, E-mail: cdervos@central.ntua.g [National Technical University of Athens, School of Electrical and Computer Eng, Zografou-15780, Athens (Greece)

    2009-07-07

    A 40 mum multilayer bi-axially oriented polypropylene (BOPP) film, was fabricated by the tenter process and its dielectric response was investigated after applying combined action of UV, humidity and heat. Dissipation factor (tan delta) and relative dielectric constant measurements were performed via the capacitance method for frequencies 20Hz-1 GHz. These results show that the relative dielectric constant (kappa') reduces towards ultra low values (1.8) with an increasing number of applied UV-condensation cycles without any subsequent increase in the dielectric loss. Having no added physical porosity and absence of fluorine atoms, the irradiated BOPP structures offer significant advantages over poly(tetrafluoroethylene) PTFE due to reduced polarization effects, lower dielectric constant values and chemical stability to the adjacent copper or aluminium conductors. Possible application fields are dry type high-voltage capacitors and insulation within electronic components.

  19. Low-?' dielectric properties of UV-treated bi-axially oriented polypropylene films

    Science.gov (United States)

    Dervos, C. T.; Tarantili, P. A.; Athanassopoulou, M. D.

    2009-07-01

    A 40 µm multilayer bi-axially oriented polypropylene (BOPP) film, was fabricated by the tenter process and its dielectric response was investigated after applying combined action of UV, humidity and heat. Dissipation factor (tan ?) and relative dielectric constant measurements were performed via the capacitance method for frequencies 20Hz-1 GHz. These results show that the relative dielectric constant (?') reduces towards ultra low values (1.8) with an increasing number of applied UV-condensation cycles without any subsequent increase in the dielectric loss. Having no added physical porosity and absence of fluorine atoms, the irradiated BOPP structures offer significant advantages over poly(tetrafluoroethylene) PTFE due to reduced polarization effects, lower dielectric constant values and chemical stability to the adjacent copper or aluminium conductors. Possible application fields are dry type high-voltage capacitors and insulation within electronic components.

  20. Low-?' dielectric properties of UV-treated bi-axially oriented polypropylene films

    International Nuclear Information System (INIS)

    A 40 ?m multilayer bi-axially oriented polypropylene (BOPP) film, was fabricated by the tenter process and its dielectric response was investigated after applying combined action of UV, humidity and heat. Dissipation factor (tan ?) and relative dielectric constant measurements were performed via the capacitance method for frequencies 20Hz-1 GHz. These results show that the relative dielectric constant (?') reduces towards ultra low values (1.8) with an increasing number of applied UV-condensation cycles without any subsequent increase in the dielectric loss. Having no added physical porosity and absence of fluorine atoms, the irradiated BOPP structures offer significant advantages over poly(tetrafluoroethylene) PTFE due to reduced polarization effects, lower dielectric constant values and chemical stability to the adjacent copper or aluminium conductors. Possible application fields are dry type high-voltage capacitors and insulation within electronic components.

  1. 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.

  2. Mechanical behaviour and microstructural evolution of alloy 800H under biaxial cyclic loading

    International Nuclear Information System (INIS)

    The mechanical behaviour of alloy 800H under biaxial cyclic loading was investigated at room temperature and at 800 C. The low-cycle fatigue experiments were carried out using tubular specimens under axial and torsional loading with constant total equivalent strain amplitude following either proportional or nonproportional loading paths. The cyclic hardening observed under nonproportional loading was clearly higher than that under proportional loading. The extra hardening due to the nonproportional loading path was more pronounced at room temperature. The evolution of the dislocation structure was characterized by transmission electron microscopy of specimens after interrupted fatigue tests. The changes in the dislocation structure and the precipitation phenomena are in accordance with the observed mechanical behaviour of the specimens. Twinning was observed in very few grains of some specimens and does not influence the extra hardening under nonproportional loading, martensite was not detected in any specimen. (orig.)

  3. A study on the validity of stress measurements in jointed crystalline rock

    International Nuclear Information System (INIS)

    In conclusion, USBM gages seem to be a good way to measure stresses in crystalline-rock block tests. Principal stresses measured within the block align very well under uniaxial stress and appear to be related to the fracture orientation under biaxial stress. Better alignment with respect to the applied stress directions would be expected to develop if higher applied stresses were attainable. Flatjack construction precluded application of pressures above 5.6 MPa. Variation of stress magnitudes within the block result in part from the difficulty in separating modulus variation from stress field variation. Determination of anisotropic elastic properties and their application in USBM gage reduction would probably improve measured stress results. Further investigations in this area are currently being pursued at CSM, in conjunction with the University of Colorado

  4. Effect of Molecular Flexibility on the Nematic-to-Isotropic Phase Transition for Highly Biaxial Molecular Non-Symmetric Liquid Crystal Dimers

    Directory of Open Access Journals (Sweden)

    María Blanca Ros

    2011-09-01

    Full Text Available In this work, a study of the nematic (N–isotropic (I phase transition has been made in a series of odd non-symmetric liquid crystal dimers, the ?-(4-cyanobiphenyl-4’-yloxy-?-(1-pyrenimine-benzylidene-4’-oxy alkanes, by means of accurate calorimetric and dielectric measurements. These materials are potential candidates to present the elusive biaxial nematic (NB phase, as they exhibit both molecular biaxiality and flexibility. According to the theory, the uniaxial nematic (NU–isotropic (I phase transition is first-order in nature, whereas the NB–I phase transition is second-order. Thus, a fine analysis of the critical behavior of the N–I phase transition would allow us to determine the presence or not of the biaxial nematic phase and understand how the molecular biaxiality and flexibility of these compounds influences the critical behavior of the N–I phase transition.

  5. Residual stresses in weld-clad reactor pressure vessel steel

    International Nuclear Information System (INIS)

    Cladding of low alloy nuclear reactor pressure vessel steel with austenitic stainless steel introduces in heavy section components high residual stresses which may cause microcrack formation in stress relief heat treatment. In this investigation an attempt is made to contribute to the solution of the stress relief cracking problem by determining quantitatively the magnitude and distribution of the residual stresses after cladding and after subsequent stress relief heat treatment. The distribution of residual stresses was determined on the basis of a combined experimental-mathematical procedure. Heavy section plate specimens of low alloy steel as base material were given an austenitic monolayer-cladding using the techniques of strip electrode and plasma hot wire cladding, respectively. A number of plates was stress relief heat treated. Starting from the cladded surface the thickness of the plates was reduced by subsequent removal of layers of material. The elastic strain reaction to the removal of each layer was measured by strain gauges. From the data obtained the biaxial residual stress distribution was computed as a function of thickness using relations which are derived for this particular case. In summary, lower residual stresses are caused by reduced thickness of the components. As the heat input, is decreased at identical base material thickness, the residual stresses are lowered also. The height of the tensile residual stress peak, however, remains approximatalstress peak, however, remains approximataly constant. In stress relief annealed condition the residual stresses in the cladding are in tension; in the base material the residual stresses are negligibly small

  6. 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

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

    Science.gov (United States)

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

    2006-01-01

    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 distribution 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 material, the hoop strains increase and the meridional stresses decrease, whereas the 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 the visco-elastic response of the gore material:

  8. Mixed spin-1/2 and spin-1 Ising model with uniaxial and biaxial single-ion anisotropy on Bethe lattice

    OpenAIRE

    Ekiz, Cesur; Strecka, Jozef; Jascur, Michal

    2008-01-01

    The mixed spin-1/2 and spin-1 Ising model on the Bethe lattice with both uniaxial as well as biaxial single-ion anisotropy terms is exactly solved by combining star-triangle and triangle-star mapping transformations with exact recursion relations. Magnetic properties (magnetization, phase diagrams and compensation phenomenon) are investigated in detail. The particular attention is focused on the effect of uniaxial and biaxial single-ion anisotropies that basically influence ...

  9. 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.

  10. Optical stress rosette based on caustics.

    Science.gov (United States)

    Theocaris, P S

    1973-02-01

    The reflected method of caustics, which is based on geometric optics, was used to define the principal stress difference and the principal directions at the interior of any generalized plane stress field by defining the stress distribution around small perforations drilled in the plate. A monochromatic coherent light beam, reflected on or transmitted through the plate at the neighborhood of the perforation, deviated by different amounts because of the refractive index variation and the thickness variation due to loading. The deviated light rays, received on a reference plane parallel to the plate, were concentrated along a singular curve, which enveloped a large part of the reflected or traversing rays and created a caustic. The properties of this singular curve were studied and found to depend on the biaxial stress field existing at the place of the perforation, as well as on the mechanical and optical properties of the material and the geometry of the optical setup. The double-kidney shape of the caustic presented a maximum diameter D(max), which coincided with one of the axes of symmetry of the caustic. The other axis of symmetry, which passed through the cusps of the caustic, coincided with the axis of maximum principal stress, while the size of D(max) yielded the principal stress difference. Thus, the caustic constitutes a sensitive stress rosette, which defines the orientation and the size of the stress field. PMID:20125294

  11. Electronic and magnetic properties of vanadium doped AlN nanosheet under in-plane biaxial strains

    Science.gov (United States)

    Cao, Huawei; Lu, Pengfei; Yu, Zhongyuan; Chen, Jun; Wang, Shumin

    2014-09-01

    First-principles calculations have been performed to investigate the electronic and magnetic properties of V-doped AlN nanosheet under in-plane biaxial strains. It is found that V atom favors to substitute for Al site with the lowest formation energy. The magnetic coupling of three different configurations are studied and configuration I is demonstrated to possess room temperature ferromagnetism. The stable ferromagnetic coupling is mediated by double exchange mechanism. In addition, the in-plane biaxial strains corresponding to tensile and compressive strains can affect and manipulate the magnetic interaction of V-doped AlN nanosheet in different ways. These results are conductive to design AlN based two dimensional diluted magnetic semiconductors.

  12. Structural and electronic properties of LaO ?-doped SrTiO3 caused by biaxial strain

    International Nuclear Information System (INIS)

    ?-doping in SrTiO3 plays a pivotal role for oxide electronics. By first-principles density functional calculations, we reveal that the electronic and structural properties of LaO ?-doped SrTiO3 can be drastically altered by compressive biaxial inplane strains. We predict the existence of a critical inplane strain (?c) above which many interesting phenomena occur, including (i) a profound symmetry breaking to the doping-induced electron states, (ii) a dramatic decline of the electron potential over a short distance of 2.5?Å near the doping layer, (iii) a new structure pattern of cation-anion displacements, and (iv) the emergence of unusual downward dispersions in the conduction bands with negative effective masses for electrons. The microscopic insight for these interesting phenomena is provided. Our study demonstrates that biaxial inplane strain can effectively modify the electronic properties in ?-doped SrTiO3 for the purpose of oxide electronics.

  13. Structural and electronic properties of LaO ?-doped SrTiO3 caused by biaxial strain

    Science.gov (United States)

    Adhikari, Rajendra; Fu, Huaxiang

    2014-09-01

    ?-doping in SrTiO3 plays a pivotal role for oxide electronics. By first-principles density functional calculations, we reveal that the electronic and structural properties of LaO ?-doped SrTiO3 can be drastically altered by compressive biaxial inplane strains. We predict the existence of a critical inplane strain (?c) above which many interesting phenomena occur, including (i) a profound symmetry breaking to the doping-induced electron states, (ii) a dramatic decline of the electron potential over a short distance of 2.5 Å near the doping layer, (iii) a new structure pattern of cation-anion displacements, and (iv) the emergence of unusual downward dispersions in the conduction bands with negative effective masses for electrons. The microscopic insight for these interesting phenomena is provided. Our study demonstrates that biaxial inplane strain can effectively modify the electronic properties in ?-doped SrTiO3 for the purpose of oxide electronics.

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

    OpenAIRE

    Geandier, Guillaume; Djaziri, Soundes; Goudeau, Philippe; Le Bourhis, Eric; Renault, Pierre-olivier; Thiaudie?re, Dominique; Hild, Franc?ois; Faurie, Damien

    2010-01-01

    We have developed on the DIFFABS-SOLEIL beamline a biaxial tensile machine working in 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) v...

  15. Biaxial Q-shearing of 27Al 3QMAS NMR spectra: insight into the structural disorder of framework aluminosilicates.

    Czech Academy of Sciences Publication Activity Database

    Kobera, Libor; Brus, Ji?í; Klein, Petr; D?de?ek, Ji?í; Urbanová, Martina

    57-58, February–April (2014), s. 29-38. ISSN 0926-2040 R&D Projects: GA ?R(CZ) GA13-24155S; GA AV ?R IAA400400904 Institutional support: RVO:61389013 ; RVO:61388955 Keywords : 27Al 3QMAS NMR * biaxial shearing * zeolites Subject RIV: JN - Civil Engineering; CF - Physical ; Theoretical Chemistry (UFCH-W) Impact factor: 2.864, year: 2013

  16. 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)

  17. Stress field in sputtered thin films: Ion irradiation as a tool to induce relaxation and investigate the origin of growth stress

    International Nuclear Information System (INIS)

    The stress state of sputtered Mo thin films was studied, and a detailed analysis of elastic strains, using x-ray diffraction and the ''sin2 ? method,'' was performed. The evolution of the lattice parameter under ion irradiation showed that the usual assumption of a biaxial stress state is not adequate to determine the true stress-free lattice parameter a0 of the film. An original stress model, including a hydrostatic component linked to volume distortions induced by point defects, is required. This model, which describes a triaxial stress field, allows a reliable determination of a0. Furthermore, ion irradiation was shown to be a powerful method for stress relaxation, providing a stress-free lattice parameter solely linked to chemical effects

  18. Biaxially textured YBa2Cu3O7-x films deposited on polycrystalline flexible yttria-stabilized zirconia ceramic substrates

    International Nuclear Information System (INIS)

    Biaxially textured YBa2Cu3O7-x (YBCO) films were grown on polycrystalline flexible yttria-stabilized zirconia (YSZ) ceramic substrates (Ceraflex) buffered with MgO and LaMnO3 layers. These substrates were initially coated with silica glass to obtain a smooth surface and then biaxially textured MgO buffer layers were deposited by ion beam assisted deposition (IBAD-MgO). Lanthanum manganate (LMO) cap layers and YBCO layers were then deposited by the pulsed laser ablation method. Highly textured YBCO films with a full width half maximum (FWHM) of 6.75 deg. in (1 1 0) phi scans and a FWHM ? 5 deg. in (2 0 0) omega scans were obtained. An initial deposition yielded samples with a Tc > 88 K and a self-field magnetization Jc of 2 x 105 A/cm2 at 77 K. A secondary ion mass spectrometry (SIMS) depth profile of the samples indicated that with the present deposition condition, some La, Mn and Mg diffusion into the YBCO layers is possible and this may reduce the Jc in the self-field. The yield strength (YS) of uncoated Ceraflex substrates was compared with that of metallic substrates and it was found that Ceraflex substrates can have a YS at least 4-5 times higher than the YS of biaxially textured Ni-5 at.%W substrates and ?1.5 times that of HastelloyTM substrates

  19. Electron diffraction from polycrystalline materials showing stress induced preferred orientation

    Science.gov (United States)

    McKenzie, D. R.; Bilek, M. M. M.

    1999-07-01

    The Gibbs free energy as generalized by J. F. Nye [Physical Properties of Crystals (Clarendon Press, Oxford, 1957), p. 179] is minimized in thermodynamic systems held at constant temperature and constant stress. This function is orientation dependent in all crystal systems in stress fields which are not purely hydrostatic. There are situations in which preferred orientation arises as a result of the synthesis of materials under impressed stress conditions such as thin film growth under ion bombardment and the pressing of powders into solids. Here, we derive the orientational constraints for cubic crystals which result from growth under a general biaxial stress field. The sign of the expression ?=s11-s12-1/2s44 determines the behavior of a cubic crystal. Electron diffraction patterns of face-centered-cubic specimens with both positive and negative values of ? are calculated using a program in MATLAB and displayed in a form suitable for direct comparison with experiment. The use of a biaxial stress with unequal principal components for producing highly oriented polycrystalline material is discussed. In the case of ? positive, as occurs in silicon, the preferred orientation is simply an alignment of the directions along the principal stresses. For ? negative, as occurs in titanium nitride, the preferred orientation depends on the ratio of the principal stresses and low index directions are aligned with the principal stresses only when the principal stresses are either equal or one of them is zero. In the general case, arc-like diffraction patterns are produced. The results of a calculation of a diffraction pattern from a cross-sectional TiN film are compared with diffraction patterns reported by L. Hultman et al. [J. Appl. Phys. 78, 5395 (1995)] and show good agreement.

  20. Uniaxial and biaxial properties of terminally sterilized porcine urinary bladder matrix scaffolds.

    Science.gov (United States)

    Freytes, Donald O; Stoner, Richard M; Badylak, Stephen F

    2008-02-01

    Scaffolds composed of extracellular matrix have been successfully used to support the reconstruction of a variety of tissues in preclinical studies and in clinical applications. As an off-the-shelf product, extracellular matrix (ECM) scaffolds must be subjected to terminal sterilization before use. The choice of sterilization method may alter the integrity of the ECM's composition and structure such that the mechanical and material properties are adversely affected. The present study evaluated selected structural properties of an ECM scaffold derived from the urinary bladder termed urinary bladder matrix after being sterilized by three different methods: ethylene oxide (ETO) (750 mg/h for 16 h), gamma irradiation (2.0 Mrads), or electron beam irradiation (e-beam) (2.2 Mrads). The structural properties that were evaluated include maximum force, maximum elongation, maximum tangential stiffness, energy dissipation, and ball-burst strength. All sterilization methods affected at least two of the measured properties. ETO was shown to have the least detrimental effect upon the measured properties. Gamma and e-beam irradiation were shown to decrease the uniaxial and biaxial strength, maximum tangential stiffness, and the energy dissipation of the ECM scaffolds. The present study showed that the choice of terminal sterilization method affects the structural properties of scaffolds composed of extracellular matrix. PMID:17618508

  1. From numerical calculations to materials testing homologation: a biaxial fatigue reliability prediction methodology for structural components

    Scientific Electronic Library Online (English)

    Daniel Muller, Spinelli; Caio de Carvalho, Scozzafave; Dirceu, Spinelli; Waldek Wladimir, Bose Filho.

    1237-12-01

    Full Text Available SciELO Brazil | Language: English Abstract in english This article investigates a fatigue approach conducted from the design phase to testing approval. It considerers modern analytical and experimental tools for structural durability assessment over each development phase for two reference components aiming an early approval methodology validation for [...] a new design. A Finite element analysis procedure was used to set critical spots for measurements minimizing the data acquisition efforts. Based on measured data, strain life calculation was done for two reference components in order to set the release goals for a new design submitted to this approach. An innovative fatigue experimental technique is proposed using component extracted specimens and an edited input cycle loads. Considering the random data from a standard test track and signal proportionality evaluation, while assuming the Brown Miller equation for bi-axial fatigue together with Ramberg-Osgood model, equivalent damage load blocks were edited and used as input for durability assessment on specimens representing the component material. The results for the three parts materials were plotted as Weibull diagram for B10 life estimation. Fatigue life results showed good correlation with the reference parts structural performance thus validating the method as well as approving the new design for production without additional on-vehicle durability testing. The methodology and the fatigue testing proposal is therefore recommended for future applications on similar developments.

  2. Bi-Axial Solar Array Drive Mechanism: Design, Build and Environmental Testing

    Science.gov (United States)

    Scheidegger, Noemy; Ferris, Mark; Phillips, Nigel

    2014-01-01

    The development of the Bi-Axial Solar Array Drive Mechanism (BSADM) presented in this paper is a demonstration of SSTL's unique space manufacturing approach that enables performing rapid development cycles for cost-effective products that meet ever-challenging mission requirements: The BSADM is designed to orient a solar array wing towards the sun, using its first rotation axis to track the sun, and its second rotation axis to compensate for the satellite orbit and attitude changes needed for a successful payload operation. The tight development schedule, with manufacture of 7 Flight Models within 1.5 year after kick-off, is offset by the risk-reduction of using qualified key component-families from other proven SSTL mechanisms. This allowed focusing the BSADM design activities on the mechanism features that are unique to the BSADM, and having an Engineering Qualification Model (EQM) built 8 months after kick-off. The EQM is currently undergoing a full environmental qualification test campaign. This paper presents the BSADM design approach that enabled meeting such a challenging schedule, its design particularities, and the ongoing verification activities.

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

    Science.gov (United States)

    Karakolis, Thomas; Callaghan, Jack P

    2015-12-01

    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

  4. Remote monitoring of bi-axial loads on a lifting surface moving unsteadily in water

    Science.gov (United States)

    Johnson, P. B.; Drake, K. R.; Eames, I.; Wojcik, A.

    2014-12-01

    A system of measuring the bi-axial load on a lifting surface (blade) which is freely moving and operates submerged in water at the laboratory scale is described. A blade with a span of 500 mm, a chord of 60 mm and a thickness of 9 mm (15% of the chord) was employed and the lift/drag forces were measured using a bespoke strain-gauge based load cell located at the mid-span of the blade, measuring bending moments in two independent directions. The requirement to move freely dictated that the load cell was encapsulated within the blade, along with signal conditioning circuitry, power supply and a data logger with wireless transmission. Submerged operation in water resulted in very short transmission distances, meaning that data were recorded and subsequently transferred using an aerial placed close to the blade while it was stationary. Assumptions based on Euler–Bernoulli beam bending theory were used to infer the total load from measurements of the bending moment at the mid-span and example data from a freely moving aerofoil on a Darrieus-type tidal energy extraction device are presented. The novelty of this system lies in its combination of free movement, submerged operation and small scale.

  5. Postbuckling analysis of multi-layered graphene sheets under non-uniform biaxial compression

    Science.gov (United States)

    Farajpour, Ali; Arab Solghar, Alireza; Shahidi, Alireza

    2013-01-01

    In this article, the nonlinear buckling characteristics of multi-layered graphene sheets are investigated. The graphene sheet is modeled as an orthotropic nanoplate with size-dependent material properties. The graphene film is subjected by non-uniformly distributed in-plane load through its thickness. To include the small scale and the geometrical nonlinearity effects, the governing differential equations are derived based on the nonlocal elasticity theory in conjunction with the von Karman geometrical model. Explicit expressions for the postbuckling loads of single- and double-layered graphene sheets with simply supported edges under biaxial compression are obtained. For numerical results, six types of armchair and zigzag graphene sheets with different aspect ratio are considered. The present formulation and method of solution are validated by comparing the results, in the limit cases, with those available in the open literature. Excellent agreement between the obtained and available results is observed. Finally, the effects of nonlocal parameter, buckling mode number, compression ratio and non-uniform parameter on the postbuckling behavior of multi-layered graphene sheets are studied.

  6. Buffer layers on metal surfaces having biaxial texture as superconductor substrates

    Science.gov (United States)

    Paranthaman, Mariappan (Knoxville, TN); Lee, Dominic F. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Goyal, Amit (Knoxville, TN)

    2000-01-01

    Buffer layer architectures are epitaxially deposited on biaxially-textured rolled substrates of nickel and/or copper and their alloys for high current conductors, and more particularly buffer layer architectures such as Y.sub.2 O.sub.3 /Ni, YSZ/Y.sub.2 O.sub.3 /Ni, RE.sub.2 O.sub.3 /Ni, (RE=Rare Earth), RE.sub.2 O.sub.3 /Y.sub.2 O.sub.3 /Ni, RE.sub.2 O.sub.3 /CeO.sub.2 /Ni, and RE.sub.2 O.sub.3 /YSZ/CeO.sub.2 /Ni, Y.sub.2 O.sub.3 /Cu, YSZ/Y.sub.2 O.sub.3 /Cu, RE.sub.2 O.sub.3 /Cu, RE.sub.2 O.sub.3 /Y.sub.2 O.sub.3 /Cu, RE.sub.2 O.sub.3 /CeO.sub.2 /Cu, and RE.sub.2 O.sub.3 /YSZ/CeO.sub.2 /Cu. Deposition methods include physical vapor deposition techniques which include electron-beam evaporation, rf magnetron sputtering, pulsed laser deposition, thermal evaporation, and solution precursor approaches, which include chemical vapor deposition, combustion CVD, metal-organic decomposition, sol-gel processing, and plasma spray.

  7. Biodegradable multilayer barrier films based on alginate/polyethyleneimine and biaxially oriented poly(lactic acid).

    Science.gov (United States)

    Gu, Chun-Hong; Wang, Jia-Jun; Yu, Yang; Sun, Hui; Shuai, Ning; Wei, Bing

    2013-02-15

    A layer-by-layer (LBL) approach was used to assemble alternating layers of sodium alginate (ALG)/polyethyleneimine (PEI) on biaxially oriented poly(lactic acid) (BOPLA) films in order to produce bio-based all-polymer thin films with low gas permeability. Increasing the depositing of ALG and PEI from 0 to 30 layers results in large thickness variations (from 0 to 3.92 ?m). After 30 ALG/PEI layers are deposited, the resulting assembly has an OTR of 1.22 cm(3)/(m(2) day atm). When multiplied by thickness, the resulting oxygen permeability (OP) is found to be less than 3.8×10(-17) cm(3) cm/cm(2) s Pa, which is almost 3 orders of magnitude lower than that of uncoated BOPLA film (1.8×10(-14) cm(3)cm/cm(2) s Pa). At the same time, the resulting multilayer-coated BOPLA films maintain high optical clarity and tensile properties. This unique barrier thin film has become a promising alternative to non-biodegradable synthetic food packaging materials. PMID:23399192

  8. 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/?m 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.

  9. Impact of Strain and Channel Thickness on Performance of Biaxial Strained Silicon MOSFETs

    Directory of Open Access Journals (Sweden)

    Neha Sharan

    2011-03-01

    Full Text Available In this paper the impact of strain and channel thickness on the performance of biaxial strained siliconMOSFET with 40 nm channel length has been analyzed by simulation in TCAD Sentaurus Simulator.With the increase in the mole fraction of germanium at the interface of the channel region, the strain inthe silicon channel increases and with it the mobility of the carriers increases and thus the drain currentincreases. The mole fraction in this paper is varied from 0 to 0.3. Other than mobility, the increase instrain also shows improvement in other performance parameters. The impact of variation in channelthickness on the functionality parameters of the MOSFET has also been analyzed. The channel thicknesscannot be increased more than the critical thickness and therefore, in this paper the thickness is variedfrom 2nm to 20 nm. It is observed that beyond 10nm the performance improvement gets saturated andtherefore the critical thickness for the channel of this structure is 10nm..

  10. Biaxial Flexural Strength of Poled Lead Zirconate Titanate under High Electric Field with Extended Field Range

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kewei [ORNL; Zeng, Fan W [ORNL; Wang, Hong [ORNL; Lin, Hua-Tay [ORNL

    2013-01-01

    In the present work, as-received poled lead zirconate titanate, or PZT 5A, was examined using ball-on-ring (BoR) mechanical testing coupled with an electric field. Electric fields in the range of 4Ec (Ec, coercive field) with controlled loading paths were applied, and mechanical tests at a substantial number of characteristic electric field levels were conducted. Commercial electronic liquid FC-40 was used to prevent the setup from dielectric breakdown under a high electric field. Weibull strength distribution was used to interpret the mechanical strength data. The data showed that the strength levels of the PZT-5A tested under OC (open circuit) in air and in FC-40 were almost the same. It was further revealed that , for the studied cases, the effect of loading history on the biaxial flexural strength of the PZT was significant in -Ec, but not in OC or zero field as well as 4Ec . An asymmetry V curve was observed for the characteristic strength-electric field graph, and the bottom of V curve was located near the negative coercive field. Microscopy analysis showed that surface-located volume-distributed flaws were the strength limiter and responsible for the failure of the tested PZT under electromechanical loadings.

  11. Reduction of initial stress stiffening by topology optimization

    DEFF Research Database (Denmark)

    Philippine, M. A.; Sigmund, Ole

    2012-01-01

    Topology optimization is a rigorous method of obtaining non-intuitive designs. We use it to obtain a capacitive RF switch that stiffens little in response to an increase of the in-plane biaxial stresses that typically develop during MEMS fabrication. The actuation voltage is closely related to the membrane's stiffness, and is more stable for a stress insensitive switch. We employ the Solid Isotropic Material with Penalization (SIMP) method with the Method of Moving Asymptotes (MMA) and a robust formulation to minimize the ratio between the compliance at a low stress level and that at a high stress level. We include a volume constraint and a compliance constraint. Topology optimized designs are compared to an intuitively-designed RF switch. The switches contain similar features. The compliance constraint is varied such that the topology optimized switch performance approaches the intuitively-designed one. Finally, the importance of the compliance constraint and of the robust formulation are discussed.

  12. 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

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

    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. 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

  14. Status of the MeLoDIE Experiment, an Advanced Device for Online Biaxial Study of the Irradiation Creep of LWR Cladding

    Energy Technology Data Exchange (ETDEWEB)

    Guimbal, Ph.; Villard, J.-F., E-mail: philippe.guimbal@cea.f [CEA, DEN, F-13108 St-Paul-lez-Durance (France); Auclair, M.; Carassou, S. [CEA, DEN, F-91191 Gif-sur-Yvette (France); Moilanen, P.; Huotilainen, S.; Patalainen, M.; Tahtinen, S. [VTT Technical Research Centre of Finland, Materials for Power Engineering, Espoo, FI-02044 VTT (Finland)

    2011-07-01

    As a prototype of future instrumented material experiments in the Jules Horowitz Reactor (JHR), the CEA in collaboration with VTT is in the process of starting the MeLoDIE experiment in the OSIRIS reactor in about a year. MeLoDIE is an initiative to go beyond the 'cook and look' concept, often used for past material experiments in MTRs. Its innovative sample holder aims to an online measurement of the biaxial creep of a LWR cladding sample under twice the typical fast neutron flux in LWRs. It is designed to perform an online-controlled biaxial loading of the sample and an online biaxial measurement of its deformation with sensors co-designed with IFE Halden. Technical challenge is to perform reliably accurate measurements under the high nuclear heat load of in-core locations while keeping within their tight space and safety constraints. (author)

  15. Lyotropic mixture made of potassium laurate/1-undecanol/K2SO4/water presenting high birefringences and large biaxial nematic phase domain: a laser conoscopy study.

    Science.gov (United States)

    Akpinar, E; Reis, D; Figueiredo Neto, A M

    2012-06-01

    The lyotropic liquid crystalline quaternary mixture made of potassium laurate (KL), potassium sulphate, 1-undecanol and water was investigated by experimental optical methods (optical microscopy and laser conoscopy). In a particular temperature and relative concentrations range, the three nematic phases (two uniaxial and one biaxial) were identified. The biaxial domain in the temperature/KL concentration surface is larger when compared to other lyotropic mixtures. Moreover, this new mixture gives nematic phases with higher birefringence than similar systems. The behavior of the symmetric tensor order parameter invariants ? (3) and ? (2) calculated from the measured optical birefringences supports that the uniaxial-to-biaxial transitions are of second order, described by a mean-field theory. PMID:22718499

  16. MATERIAL CHARACTERIZATION BY AN INNOVATIVE BIAXIAL SHEAR EXPERIMENT AT VERY LARGE STRAINS AND AT VERY HIGH STRAIN RATES

    OpenAIRE

    Albertini, C.; Griffiths, L.; Montagnani, M.; Rodis, A.; Mariotti, P.; Paluffi, A.; Pazienza, G.

    1991-01-01

    In order to measure the material properties in the conditions of metal cutting, wire drawing and missile penetration, a biaxial shear experiment has been performed at very large strains (~ 4) and at very high strain rate (0.4x105 s-1) using a special specimen having a thin (0.25 mm) ring-shaped gauge part. The loading device is a tension-torsion Hopkinson bar apparatus which can be used also at low and medium strain rate. A special electroptical technique has been developed for the direct mea...

  17. Reduction of critical current density in a spin valve with a perpendicular polarizer and a planar biaxial free layer

    International Nuclear Information System (INIS)

    Ultrafast magnetization switching of a spin valve consisting of a perpendicularly magnetized polarizer and an in-plane magnetized free layer with uniaxial and higher order anisotropy is studied. Here we report the analytical results in which a modified asteroid and current-field state diagram are derived from an effective one-dimensional free energy for higher order anisotropy. Because additional crystalline axes provide an additional nutation channel, the critical current density for the biaxial case is smaller than that commonly observed for quadratic anisotropy. This will be of importance for the design of spin-torque-transfer magnetic random access memories and nano-oscillators.

  18. Catalytic surface modification of roll-milled poly(?-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 ?m thick poly(?-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

  19. 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.

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

    OpenAIRE

    Frencken, Jo E.; Laura Brain Lascano; Ignacio Mazzola; Ricardo Juan Cabral; Molina, Gustavo Fabi Amp Xe N.

    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, 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 (Gr...

  1. A Study in Three-Dimensional Chaotic Dynamics: Granular Flow and Transport in a Bi-Axial Spherical Tumbler

    OpenAIRE

    Christov, Ivan C.; Lueptow, Richard M.; Ottino, Julio M.; Sturman, Rob

    2014-01-01

    We study 3D chaotic dynamics through an analysis of transport in a granular flow in a half-full spherical tumbler rotated sequentially about two orthogonal axes (a bi-axial "blinking" tumbler). The flow is essentially quasi-2D in any vertical slice of the sphere during rotation about a single axis, and we provide an explicit exact solution to the model in this case. Hence, the cross-sectional flow can be represented by a twist map, allowing us to express the 3D flow as a lin...

  2. Stress anisotropy and stress gradient in magnetron sputtered films with different deposition geometries

    International Nuclear Information System (INIS)

    Mo films were deposited via magnetron sputtering with two different deposition geometries: dynamic deposition (moving substrate) and static deposition (fixed substrate). The residual stress and structural morphologies of these films were investigated, with particular focus on in-plane anisotropy of the biaxial stress and stress gradient across the film thickness. The results revealed that the Mo films developed distinct states of residual stress, which depended on both deposition geometry and film thickness. With the dynamic geometry, the Mo films generally exhibited anisotropic stress. Both the degree of anisotropy and the magnitude of stress varied as functions of film thickness. The variation of stress was linked to the evolution of anisotropic microstructures in the films. The Mo films from the static geometry developed isotropic residual stress, which was more compressive and noticeably larger in magnitude than that of the Mo films from the dynamic geometry. Aside from these disparities, the two types of Mo films (i.e., anisotropic and isotropic) exhibited notably similar trends of stress variation with film thickness. Depth profiling indicated the presence of large stress gradients for the Mo films, irrespective of the deposition geometries. This observation seems to be consistent with the premise that Mo films develop a zone T structure, which is inherently inhomogeneous along the film thickness. Moreover, the largest stress gradient for both types of depositiotress gradient for both types of deposition geometries arises at roughly the same film depth (?240 nm from substrate), where the stresses sharply transits from highly compressive to less compressive or even tensile. This appears to correspond to the boundary region that separates two distinct stages of microstructural evolution, a feature unique to zone T-type structure

  3. Theoretical and experimental research of stress measurement by means of ultrasonic wave attenuation method

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Y.; Peng, S.S. (China University of Mining and Technology (China))

    1992-12-01

    The feasibility of using the ultrasonic wave attenuation method for measuring stress was examined theoretically and experimentally. The theoretical analyses showed that for a given rock type the relation between strees and attenuation coefficient ratio could be expressed approximately by second order polynomials. Combining the elastic and statistical theories, the authors set up a theoretical model for stress measurement by using the ultrasonic wave attenuation method, and predicted the magnitudes and directions of the existing principal stresses around the borehole. The experimental study consists of the following: the attenuation measurements in core specimens under uniaxial stress and the attenuation measurements in boreholes drilled through blocks of sandstone, limestone, and granite subjected to externally applied uniaxial or biaxial compressional stresses. In the experiments, only longitudinal wave is used. The results demonstrate that it is feasible to measure the stresses of virgin rocks by using the ultrasonic wave attentuation method. 14 refs., 6 figs., 4 tabs.

  4. Manage Stress

    Science.gov (United States)

    ... Conditions and Diseases > Heart Health > Manage Stress Manage Stress The Basics Take Action! Ver en español Content ... on: March 01, 2015 The Basics Not all stress is bad. Stress can help protect you in ...

  5. About the effect of biaxial anisotropy of ferrite-garnet films with magnetization in a film plane direction on the shape of pulsed remagnetization curves

    International Nuclear Information System (INIS)

    The curves of pulsed magnetization reversal in iron garnet films with easy-plane anisotropy are studied. Magnetization reversal is initiated by a pulsed magnetic field aligned with the axis of biaxial anisotropy lying in the plane of the film. The curves exhibit kinks at fields close to the effective field of biaxial anisotropy. Magnetization reversal mechanisms in fields above and below the inflection point are discussed. The results of the study obtained for the films of the compositions (LuBi)3(FeGa)5O12 and (YLuBi)3(FeGa)5O12 are provided

  6. Strain versus stress in a model granular material: A Devil's staircase

    Science.gov (United States)

    Combe; Roux

    2000-10-23

    The series of equilibrium states reached by disordered packings of rigid, frictionless disks in two dimensions, under gradually varying stress, are studied by numerical simulations. Statistical properties of trajectories in configuration space are found to be independent of specific assumptions ruling granular dynamics, and determined by geometry only. A monotonic increase in some macroscopic loading parameter causes a discrete sequence of rearrangements. For a biaxial compression, we show that, due to the statistical importance of such events of large magnitude, the dependence of the resulting strain on stress direction is a Levy flight in the thermodynamic limit. PMID:11030967

  7. Strain versus stress in a model granular material a Devil's staircase

    CERN Document Server

    Combe, G; Combe, Gael; Roux, Jean-Noel

    2000-01-01

    The series of equilibrium states reached by disordered packings of rigid, frictionless discs in two dimensions, under gradually varying stress, are studied by numerical simulations. Statistical properties of trajectories in configuration space are found to be independent of specific assumptions ruling granular dynamics, and determined by geometry only. A monotonic increase in some macroscopic loading parameter causes a discrete sequence of rearrangements. For a biaxial compression, we show that, due to the statistical importance of such events of large magnitudes, the dependence of the resulting strain on stress direction is a Levy flight in the thermodynamic limit.

  8. The influence of quench sensitivity on residual stresses in the aluminium alloys 7010 and 7075

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, J.S., E-mail: jeremy.robinson@ul.ie [Materials and Surface Science Institute, University of Limerick (Ireland); Tanner, D.A. [Materials and Surface Science Institute, University of Limerick (Ireland); Truman, C.E. [Department of Mechanical Engineering, University of Bristol (United Kingdom); Paradowska, A.M. [ISIS Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Wimpory, R.C. [Helmholtz Centre Berlin for Materials and Energy, Hahn Meitner Platz 1, Berlin (Germany)

    2012-03-15

    The most critical stage in the heat treatment of high strength aluminium alloys is the rapid cooling necessary to form a supersaturated solid solution. A disadvantage of quenching is that the thermal gradients can be sufficient to cause inhomogeneous plastic deformation which in turn leads to the development of large residual stresses. Two 215 mm thick rectilinear forgings have been made from 7000 series alloys with widely different quench sensitivity to determine if solute loss in the form of precipitation during quenching can significantly affect residual stress magnitudes. The forgings were heat treated and immersion quenched using cold water to produce large magnitude residual stresses. The through thickness residual stresses were measured by neutron diffraction and incremental deep hole drilling. The distribution of residual stresses was found to be similar for both alloys varying from highly triaxial and tensile in the interior, to a state of biaxial compression in the surface. The 7010 forging exhibited larger tensile stresses in the interior. The microstructural variation from surface to centre for both forgings was determined using optical and transmission electron microscopy. These observations were used to confirm the origin of the hardness variation measured through the forging thickness. When the microstructural changes were accounted for in the through thickness lattice parameter, the residual stresses in the two forgings were found to be very similar. Solute loss in the 7075 forging appeared to have no significant effect on the residual stress magnitudes when compared to 7010. - Highlights: Black-Right-Pointing-Pointer Through thickness residual stress measurements made on large Al alloy forgings. Black-Right-Pointing-Pointer Residual stress characterised using neutron diffraction and deep hole drilling. Black-Right-Pointing-Pointer Biaxial compressive surface and triaxial subsurface residual stresses. Black-Right-Pointing-Pointer Quench sensitivity of 7075 promotes significant microstructural differences to 7010. Black-Right-Pointing-Pointer When precipitation is accounted for, residual stress in both forgings are similar.

  9. The influence of quench sensitivity on residual stresses in the aluminium alloys 7010 and 7075

    International Nuclear Information System (INIS)

    The most critical stage in the heat treatment of high strength aluminium alloys is the rapid cooling necessary to form a supersaturated solid solution. A disadvantage of quenching is that the thermal gradients can be sufficient to cause inhomogeneous plastic deformation which in turn leads to the development of large residual stresses. Two 215 mm thick rectilinear forgings have been made from 7000 series alloys with widely different quench sensitivity to determine if solute loss in the form of precipitation during quenching can significantly affect residual stress magnitudes. The forgings were heat treated and immersion quenched using cold water to produce large magnitude residual stresses. The through thickness residual stresses were measured by neutron diffraction and incremental deep hole drilling. The distribution of residual stresses was found to be similar for both alloys varying from highly triaxial and tensile in the interior, to a state of biaxial compression in the surface. The 7010 forging exhibited larger tensile stresses in the interior. The microstructural variation from surface to centre for both forgings was determined using optical and transmission electron microscopy. These observations were used to confirm the origin of the hardness variation measured through the forging thickness. When the microstructural changes were accounted for in the through thickness lattice parameter, the residual stresses in the two forgings were found to be very similar. S forgings were found to be very similar. Solute loss in the 7075 forging appeared to have no significant effect on the residual stress magnitudes when compared to 7010. - Highlights: ? Through thickness residual stress measurements made on large Al alloy forgings. ? Residual stress characterised using neutron diffraction and deep hole drilling. ? Biaxial compressive surface and triaxial subsurface residual stresses. ? Quench sensitivity of 7075 promotes significant microstructural differences to 7010. ? When precipitation is accounted for, residual stress in both forgings are similar.

  10. Preparation of biaxially aligned cubic zirconia films on pyrex glass substrates using ion-beam assisted deposition

    Science.gov (United States)

    Sonnenberg, N.; Longo, A. S.; Cima, M. J.; Chang, B. P.; Ressler, K. G.; McIntyre, P. C.; Liu, Y. P.

    1993-07-01

    Yttria stabilized zirconia films were deposited using ion-assisted, electron beam deposition (IBAD) on pyrex glass substrates heated to 600 °C. Films deposited under these conditions without IBAD exhibit fiber texture such that preferred (100) orientation exists perpendicular to the substrate. The orientation of the films has been studied as a function of ion bombardment angle, deposition rate, ion current density, and ion beam energy. Films deposited with IBAD at bombardment angles of less than 63° display strong (100) preferred orientation perpendicular to the substrate. Films having ion to atom ratios of 0.05 exhibit (220) biaxial alignment in the plane of the film. Best results were achieved for films with deposition rates of 2.4 Å/s, beam energies of 75 eV and ion fluences of 18 ?A/cm2. Increasing the beam energy to 300 eV increases the concentration of wire texture in these films. Films deposited at higher ion/atom ratios (0.11 and 0.25) produce films with alignments highly dependent on the angle of ion bombardment. Processing conditions have been shown, therefore, to effect absolute orientation, and not just the quality of the pre-existing orientation. The microstructures of the biaxially aligned films have been studied and this has allowed for a clarification of the growth mechanism of these films. A growth instability of the differing orientations during ion bombardment is shown to cause in-plane alignment rather than preferential etching of misoriented nuclei.

  11. Fabrication of hydroxyapatite-poly(epsilon-caprolactone) scaffolds by a combination of the extrusion and bi-axial lamination processes.

    Science.gov (United States)

    Sun, Jong-Jae; Bae, Chang-Jun; Koh, Young-Hag; Kim, Hyoun-Ee; Kim, Hae-Won

    2007-06-01

    Hydroxyapatite (HA)/poly(epsilon-caprolactone) (PCL) composite scaffolds were fabricated using a combination of the extrusion and bi-axial lamination processes. Firstly, HA/PCL composites with various HA contents (0, 50, 60, 70 wt%) were prepared by mixing the HA powders and the molten PCL at 100 degrees C and then extruded through an orifice with dimensions of 600 x 600 microm to produce HA/PCL composite fibers. Isobutyl methacrylate (IBMA) polymer fiber was also prepared in a similar manner for use as a fugitive material. The 3-D scaffold was then produced by the bi-axial lamination of the HA/PCL and IBMA fibers, followed by solvent leaching to remove the IBMA. It was observed that the HA/PCL composites had a superior elastic modulus and biological properties, as compared to the pure PCL. The fabricated HA/PCL scaffold showed a controlled pore structure (porosity of approximately 49% and pore size of approximately 512 microm) and excellent welding between the HA/PCL fibers, as well as a high compressive strength of approximately 7.8 MPa. PMID:17242998

  12. Structural and electronic properties of LaO ?-doped SrTiO{sub 3} caused by biaxial strain

    Energy Technology Data Exchange (ETDEWEB)

    Adhikari, Rajendra; Fu, Huaxiang [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

    2014-09-28

    ?-doping in SrTiO{sub 3} plays a pivotal role for oxide electronics. By first-principles density functional calculations, we reveal that the electronic and structural properties of LaO ?-doped SrTiO{sub 3} can be drastically altered by compressive biaxial inplane strains. We predict the existence of a critical inplane strain (?{sub c}) above which many interesting phenomena occur, including (i) a profound symmetry breaking to the doping-induced electron states, (ii) a dramatic decline of the electron potential over a short distance of 2.5?Å near the doping layer, (iii) a new structure pattern of cation-anion displacements, and (iv) the emergence of unusual downward dispersions in the conduction bands with negative effective masses for electrons. The microscopic insight for these interesting phenomena is provided. Our study demonstrates that biaxial inplane strain can effectively modify the electronic properties in ?-doped SrTiO{sub 3} for the purpose of oxide electronics.

  13. Effect of biaxial strain and composition on vacancy mediated diffusion in random binary alloys A first principles study of the SiGe system

    CERN Document Server

    Ramanarayanan, P; Clemens, B M; Ramanarayanan, Panchapakesan; Cho, Kyeongjae; Clemens, Bruce M.

    2002-01-01

    We present the results of a systematic study using the density functional theory (within the local density approximation) of the effects of biaxial strain and composition on the self-diffusion of Si and Ge in SiGe alloys diffusing by a vacancy mechanism. The biaxial strain dependence of the vacancy formation energy was reconfirmed with previous calculations. The effect of biaxial strain on the interaction potential energy between a substitutional Ge atom and a vacancy was calculated. These calculations were used to estimate the change in the activation energy (due to biaxial strain) for the self-diffusion of Si and Ge in Si by a vacancy mechanism. The composition dependence of the vacancy formation energy was calculated. A database of ab initio migration energy barriers for vacancy migration in different local environments was systematically developed by considering the effect of the first nearest neighbor sites explicitly and the effect of the other sites by a mean field approximation. A kinetic Monte Carlo ...

  14. Biaxial and antiferroelectric structure of the orthogonal smectic phase of a bent-shaped molecule and helical structure in a chiral mixture system

    Science.gov (United States)

    Kang, Sungmin; Nguyen, Ha; Nakajima, Shunpei; Tokita, Masatoshi; Watanabe, Junji

    2013-05-01

    We examined the biaxial and antiferroelectric properties in the Smectic-APA (Sm-APA) phase of bent-shaped DC-S-8. The biaxiality, which results from the existence of a secondary director, was well established from birefringence observations in the homeotropically aligned Sm-APA. By entering into Sm-APA phase, the birefringence (?n, difference between two refractive indices of short axes) continuously increased from 0 to 0.02 with decreasing temperature. The antiferroelectric switching and second harmonic generation (SHG) activity on the field-on state were also observed in the Sm-APA phase, and the evaluated spontaneous polarization (PS) value strongly depended on temperature. The temperature dependence of ?n and PS resembles each other and follows Haller's approximation, showing that the biaxiality is due to polar packing in which the molecules are preferentially packed with their bent direction arranged in the same direction, and that the phase transition of Sm-APA to Sm-A is second order. The biaxiality was further examined in chiral Sm-APA*. Doping with chiral components induced the helical twisting of the secondary director in the Sm-APA* phase, which was confirmed by observing the reflection of the circular dichroism (CD) bands in the homeotropically aligned cell. The helical pitch of Sm-APA* is tunable in the range of 300-700 nm wavelength with a variation in the chiral content of 5 to 10 weight (wt)%.

  15. Mechanical response of cross-ply Si{sub 3}N{sub 4}/BN fibrous monoliths under uniaxial and biaxial loadings

    Energy Technology Data Exchange (ETDEWEB)

    Singh, D.; Cruse, T. A.; Hermanson, D. J.; Goretta, K. C.; Zok, F. W.; McNulty, J. C.

    2000-03-01

    Mechanical properties of hot-pressed Si{sub 3}N{sub 4}/BN fibrous monoliths (FMs) were evaluated under ambient conditions in four-point and biaxial flexure modes. Effects of cell orientation, 0{degree}/90{degree} and {+-}45{degree}, on elastic modulus and fracture strength of the FMs were investigated. Fracture surfaces were examined by scanning electron microscopy.

  16. Effect of Low Pressure Nitrogen DC Plasma on Optical Properties of Biaxial-Oriented Polypropylene (BOPP), Poly Methyl Methacrylate (PMMA) and Poly Vinyl Chloride (PVC) Films

    Science.gov (United States)

    Mortazavi, S. H.; Ghoranneviss, M.; Faryadras, S.

    2012-06-01

    In this paper properties of Biaxial-Oriented Polypropylene, Poly Vinyl Chloride and Poly Methyl Methacrylate samples treated by DC glow discharge of N2 plasma have been investigated by UV-Vis_NIR spectrophotometer. It was found that plasma treatment change chemical structure of polymer surfaces. In addition, absorption coefficient, refractive index and extinction coefficient of all treated samples have been slightly changed.

  17. The effect of viscosity and activation mode on biaxial flexure strength and modulus of dual resin cements / Efeito da viscosidade e modo de ativação na resistência flexural biaxial e módulo em cimentos resinosos duais

    Scientific Electronic Library Online (English)

    Marina Di, Francescantonio; Frederick Allen, Rueggeberg; Cesar Augusto Galvão, Arrais; Glaucia Maria Bovi, Ambrosano; Marcelo, Giannini.

    Full Text Available SciELO Brazil | Language: English Abstract in portuguese OBJETIVO: O objetivo do estudo é avaliar o efeito do modo de ativação na resistência flexual biaxial (RF) e módulo (MF) em cimentos resinosos duais. METODOLOGIA: Foram formados oito grupos experientais (n=12) de acordo com cimento resinos (Nexus 2/Kerr Corp. and Variolink II/IvoclarVivadent), modo d [...] e ativação (dual ou auto-polimerizado) e viscosidade (baixa e alta). Quarenta e oito discos de cada cimento foram fabridados (0,5 mm espessura por 6,0 mm diametro). Metade dos espécimes foram foto-ativados e a outra metade foi deixado para auto-polimerização. Após dez dias, o teste biaxial foi realizado em máquina de ensaio universal (1,27 mm/min, Instron 5844). Os dados foram analisados estatisticamente por ANOVA e teste Tukey (5%). RESULTADOS: A foto-ativação aumentou a RF e RM para os cimentos em ambas as viscosidades em comparação com os grupos auto-polimerizados. A versão alta viscosidade dos cimentos foto-ativados apresentou maior RF que os cimentos em baixa viscosidade. A viscosidade e o tipo de cimento não influenciam o MF. A foto-ativação aumenta os valores de RF e MF para ambos os cimentos e viscosidades. CONCLUSÃO: O uso de diferentes cimentos com diferentes viscosidades pode influenciar o comportamento biomecânico de cimentos resinoso. Abstract in english PURPOSE: The aim of this study was to evaluate the effects of curing mode and viscosity on the biaxial flexural strength (FS) and modulus (FM) of dual resin cements. METHODS: Eight experimental groups were created (n=12) according to the dual-cured resin cements (Nexus 2/Kerr Corp. and Variolink II/ [...] IvoclarVivadent), curing modes (dual or self-cure), and viscosities (low and high). Forty-eight cement discs of each product (0.5 mm thick by 6.0 mm diameter) were fabricated. Half specimens were light - activated for 40 seconds and half were allowed to self-cure. After 10 days, the biaxial flexure test was performed using a universal testing machine (1.27 mm/min, Instron 5844). Data were statistically analyzed by three-way ANOVA and Tukey's test (5%). RESULTS: Light-activation increased FS and FM of resin cements at both viscosities in comparison with self-curing mode. The high viscosity version of light-activated resin cements exhibited higher FS than low viscosity versions. The viscosity of resin and the type of cement did not influence the FM. Light-activation of dual-polymerizing resin cements provided higher FS and FM for both resin cements and viscosities. CONCLUSION: The use of different resin cements with different viscosities may change the biomechanical behavior of these luting materials.

  18. Stress incontinence

    Science.gov (United States)

    Incontinence - stress ... over 2 cups of urine in their bladder. Stress incontinence occurs when the muscles that control your ... the pelvic area or the prostate (in men) Stress incontinence is the most common type in women. ...

  19. Cold Stress

    Science.gov (United States)

    ... Workplace Safety & Health Topics NIOSH Share Compartir COLD STRESS On this Page Overview Types of Cold Stress ... access to important safety information. Types of Cold Stress Hypothermia | Cold Water Immersion | Frostbite | Trench Foot | Chilblains ...

  20. Managing Stress

    Science.gov (United States)

    ... page It's been added to your dashboard . Managing stress 3:13 Pregnancy is a stressful time for ... Here are practical suggestions to help you manage stress. Stanford Prematurity 5:57 Babies on Broadway 2: ...

  1. Managing Stress

    Medline Plus

    Full Text Available ... page It's been added to your dashboard . Managing stress 3:13 Pregnancy is a stressful time for ... Here are practical suggestions to help you manage stress. Stanford Prematurity 5:57 Babies on Broadway 2: ...

  2. Managing Stress

    Medline Plus

    Full Text Available ... page It's been added to your dashboard . Managing stress 3:13 Pregnancy is a stressful time for ... Here are practical suggestions to help you manage stress. Ovulation and pregna 3:13 2011 National Ambass ...

  3. Managing Stress

    Medline Plus

    Full Text Available ... page It's been added to your dashboard . Managing stress 3:13 Pregnancy is a stressful time for ... Here are practical suggestions to help you manage stress. March of Dimes 75th 2:00 Partner category ...

  4. Bi-axial magnetic orientation in a twinned ErBa2Cu3Oy superconductor by controlling grain size

    International Nuclear Information System (INIS)

    Bi-axial magnetic orientation in ErBa2Cu3Oy (Er123) superconductor with a twinned microstructure was demonstrated. A ball-milling process effectively improved the degree of the in-plane and c-axis orientation of Er123 powder samples oriented in a modulated rotating magnetic field of 10 T. From the relationship between the particle size and the degree of orientation, it is concluded that pulverization induced the appearance of the in-plane magnetic anisotropy of Er123 grains through inhomogenization of two different types of domains in their grains. The present study presents a production technique of RE123 bulk magnets and coated conductors without epitaxy technology.

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

    CERN Document Server

    Kim, Young-ki; 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 surface orientation of the director changes from tangential (parallel to the bounding plates) to tilted. Each domain wall separates two regions with the director tilted in opposite azimuthal directions. At the centre of the wall, the director remains parallel to the bonding plates. The domain walls can be easily removed by applying a modest electric field. The anchoring transition is explained by the balance of (a) the intrinsic perpendicular surface anchoring produced by the polyimide aligning layer and (b) tangential alignme...

  6. Self-field ac losses in biaxially aligned Y endash Ba endash Cu endash O tape conductors

    International Nuclear Information System (INIS)

    Self-field ac losses were measured by the conventional ac four-probe method in biaxially aligned Y endash Ba endash Cu endash O tapes using polycrystalline Hastelloy tapes with textured yttria-stabilized-zirconia buffer layers. The ac losses increased in proportion to the fourth power of transport current in the high Jc sample, and agreed well with Norris close-quote equation for thin strip conductors. However, the low Jc sample had rather higher losses than Norris close-quote prediction, suggesting excessive magnetic flux penetration caused by percolated current paths. The results confirmed Norris close-quote prediction of the low ac losses for thin strip conductors, and indicated the importance of removing percolated structures of current paths to avoid higher ac losses than the theoretical predictions based on uniform conductors. copyright 1997 American Institute of Physics

  7. Spin phase interference in magnetization tunneling at excited levels of biaxial ferromagnets in an arbitrarily directed magnetic field

    CERN Document Server

    Lü, R; Kou, S P; Zhou, Y; Gu, B L; Lu, Rong; Zhu, Jia-Lin; Kou, Su-Peng; Zhou, Yi; Gu, Bing-Lin

    2000-01-01

    The quantum interference effects induced by the Wess-Zumino term, or Berry phase are studied theoretically in resonant quantum tunneling of the magnetization vector between degenerate states in nanometer-scale single-domain ferromagnets with biaxial symmetry in an external magnetic field at an arbitrarily directed angle in the $ZY$ plane. We calculate analytically the tunnel splittings between degenerate excited levels of neighboring wells with the help of the periodic instanton method in the spin-coherent-state path-integral representation. The low-lying energy level spectrum of $n$-th excited state is found by applying the Bloch theorem in one-dimensional periodic potential, and by calculating the Euclidean transition amplitude, respectively. The energy level spectrum for integer total spins is significantly different from that for half-integer spins. The topological phase interference effects are found to depend on the orientation of the external magnetic field distinctly. The transition from classical to ...

  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

    2009-01-01

    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 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 for a speed range of 50 to 2000 rpm. A method for initial rotor position of BEGA is proposed based on injection of a very short voltage pulse in the machine dc excitation, the method being independency of machine parameters. Experimental results for initial rotor position estimation proved accuracy below 10 electrical degrees in less than 2 ms test time.

  9. Engineering of optical polarization based on electronic band structures of A-plane ZnO layers under biaxial strains

    Energy Technology Data Exchange (ETDEWEB)

    Matsui, Hiroaki, E-mail: hiroaki@ee.t.u-tokyo.ac.jp; Tabata, Hitoshi [Department of Bioengineering, The University of Tokyo, 1-3-7 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Electrical Engineering and Information Systems, The University of Tokyo, 1-3-7 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Hasuike, Noriyuki; Harima, Hiroshi [Department of Electronics and Information Science, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585 (Japan)

    2014-09-21

    In-plane anisotropic strains in A-plane layers on the electronic band structure of ZnO were investigated from the viewpoint of optical polarization anisotropy. Investigations utilizing k·p perturbation theory revealed that energy transitions and associated oscillation strengths were dependent on in-plane strains. The theoretical correlation between optical polarizations and in-plane strains was experimentally demonstrated using A-plane ZnO layers with different in-plane strains. Finally, optical polarization anisotropy and its implications for in-plane optical properties are discussed in relation to the energy shift between two orthogonal directions. Higher polarization rotations were obtained in an A-plane ZnO layer with in-plane biaxially compressive strains as compared to strain-free ZnO. This study provides detailed information concerning the role played by in-plane strains in optically polarized applications based on nonpolar ZnO in the ultra-violet region.

  10. Correlation of residual strength with acoustic emission from impact-damaged composite structures under constant biaxial load

    Science.gov (United States)

    Hamstad, M. A.; Whittaker, J. W.; Brosey, W. D.

    1992-01-01

    Small, filament-wound, Kevlar/epoxy, biaxial test specimens were subjected to various levels of impact damage. The specimens were pressurized in a proof test cycle to 58 percent of their nominal, undamaged strength and then pressurized to failure. Acoustic emission data were gathered by multiple sensors during a 10 minute hold at peak proof pressure. Post-test filtering of the data was performed to study composite behavior in the damaged region and other areas. The rate and total amount of AE produced depends on the duration of the static load and degree of damage. The concept of the event rate moment is introduced as a method of quantifying a structure's total AE behavior when under static load. Average event rate, total long duration events, and event rate moments provided various degrees of correlation between AE and residual strength.

  11. Engineering of optical polarization based on electronic band structures of A-plane ZnO layers under biaxial strains

    International Nuclear Information System (INIS)

    In-plane anisotropic strains in A-plane layers on the electronic band structure of ZnO were investigated from the viewpoint of optical polarization anisotropy. Investigations utilizing k·p perturbation theory revealed that energy transitions and associated oscillation strengths were dependent on in-plane strains. The theoretical correlation between optical polarizations and in-plane strains was experimentally demonstrated using A-plane ZnO layers with different in-plane strains. Finally, optical polarization anisotropy and its implications for in-plane optical properties are discussed in relation to the energy shift between two orthogonal directions. Higher polarization rotations were obtained in an A-plane ZnO layer with in-plane biaxially compressive strains as compared to strain-free ZnO. This study provides detailed information concerning the role played by in-plane strains in optically polarized applications based on nonpolar ZnO in the ultra-violet region.

  12. Anisotropic dynamics of optical vortex-beam propagating in biaxial crystals: a numerical method based on asymptotic expansion.

    Science.gov (United States)

    Lu, Xiancong; Chen, Lixiang

    2013-04-01

    One difficulty of angular spectrum representation method in studying optical propagation inside anisotropic crystals is to calculate the double integrals containing highly oscillating functions. In this paper, we introduce an accuracy and numerically cheap method based on asymptotic expansion theory to overcome this difficulty, which therefore allows to compute optical fields with arbitrary incident beam and is not restricted to the paraxial limit. This numerical method is benchmarked against the analytical solutions in uniaxial crystals and excellent agreements between them are obtained. As an application, we adopt it to investigate the propagation of a Gaussian vortex-beam in a biaxial crystal. The general features of anisotropic dynamics and power conversion between field components are revealed. The numerical results is interpreted by making appropriate analytical approximation to the wave equations. PMID:23571939

  13. Behavior of annealed type 316 stainless steel under monotonic and cyclic biaxial loading at room temperature

    International Nuclear Information System (INIS)

    The elastic-plastic behavior of type 316 stainless steel at room temperature was studied. The stress-limited loading was restricted to two relatively simple histories, and since hardening under cyclic conditions is a concern in design, the yield behavior of type 316 stainless steel after several cycles of strain-limited loading was investigated

  14. Effects of deposition temperature and thermal cycling on residual stress state in zirconia-based thermal barrier coatings

    International Nuclear Information System (INIS)

    Advanced ceramic multilayered coatings are commonly used as protective coatings for engine metal components to improve performance, e.g. thermal barrier coatings (TBCs). Zirconia-based TBCs were produced by plasma spraying process and characterized in terms of microstructure, porosity, elastic modulus, adherence and residual stresses. In this contribution the residual stresses in multilayered coatings applied on Ni based superalloys for use as thermal barrier coatings were studied both by numerical modelling and experimental stress measurement. The thermal residual stresses generated during the spraying process of duplex TBCs were simulated by using an heat transfer finite element program and an elasto-plastic biaxial stress model. The TBC system was subjected to different thermal cycling conditions (maximum temperature, heating up and cooling down rates, dwell time at maximum temperature, etc.). The stress distribution within the TBC was also modelled after thermal cycling. The stress state in the as-deposited and in thermally cycled coatings was verified using an X-ray diffraction technique. The measurements were in good agreement with the residual stress modelled calculations. It was observed that the residual stresses were dependent on the thermal history of the TBC (as-deposited and thermally cycled). It is proposed that thermal cycling allowed the stresses to relax by microcracking and creep mechanisms at high temperature such that on cooling down to room tempere such that on cooling down to room temperature, an in-plane biaxial compressive stress will arise on the zirconia top coating due to the difference on the coefficients of thermal expansion between the metallic substrate and ceramic coating material. (orig.)

  15. Effect of an external magnetic field on the nematic-isotropic phase transition in mesogenic systems of uniaxial and biaxial molecules: A Monte Carlo study

    Science.gov (United States)

    Ghoshal, Nababrata; Mukhopadhyay, Kisor; Roy, Soumen Kumar

    2014-04-01

    We determine the nematic-isotropic coexistence curve terminating at the critical point in a temperature-external field phase diagram for nematic liquid crystals with positive diamagnetic anisotropy, where the molecules are either perfectly uniaxial or biaxial using computer simulation of a lattice model. The coexistence curve is much steeper than that predicted by the standard Landau-de Gennes and Maier-Saupe mean-field theories. For the uniaxial system the critical magnetic field is estimated to be one order of magnitude lower than the mean-field estimate but of the same order of magnitude as the experimental measurement. Our study shows that molecular biaxiality could reduce the critical field strength significantly.

  16. 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)

  17. Epitaxial growth of CeO2/yttria-stabilized ZrO2 double layer films on biaxially textured Ni tape via electrostatic spray assisted vapour deposition

    International Nuclear Information System (INIS)

    Epitaxial growth of CeO2 and yttria-stabilized ZrO2 (YSZ) double layer films has been successfully carried out on biaxially textured nickel substrates at a temperature between 400 and 600 deg. C using electrostatic spray assisted vapour deposition method. The structure of the double layer was characterized by X-ray diffraction and scanning electron microscopy. The results show that highly oriented CeO2/YSZ double buffer films were formed epitaxially onto biaxially textured Ni substrates. The orientation relationships between YSZ layer and Ni substrate are 001YSZ//001Ni and 110YSZ//100Ni, while the orientation relationships between CeO2 and YSZ are 001CeO2//001YSZ and 100CeO2//100YSZ

  18. Polarization Manipulation via Orientation Control in Polycrystalline BiFeO3 Thin Films on Biaxially Textured, Flexible Metallic Tapes

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Junsoo [ORNL; Goyal, Amit [ORNL; Jesse, Stephen [ORNL; Heatherly Jr, Lee [ORNL

    2011-01-01

    (111)-, (101)-, and (001)-oriented polycrystalline BiFeO3 films were fabricated on rolling-assisted biaxially textured substrates (RABiTS) with appropriate, buffer layer engineering of heteroepitaxially grown buffer multilayers on RABiTS. The crystallographic orientation and polarization direction were confirmed using X-ray diffraction and piezoresponse force microscopy (PFM), respectively. All the films exhibited excellent ferroelectric properties. Switching spectroscopy PFM demonstrated that the switching polarization in (111)-oriented polycrystalline BiFeO3 films is higher than (101) or (001) oriented films. These high-quality, BiFeO3 films on low-cost, flexible, biaxially textured metallic tapes with controllable orientation and polarization are attractive for application in flexible ferroelectric devices.

  19. Investigation of the interaction of alkali ions with surfactant head groups for the formation of lyotropic biaxial nematic phase via optical birefringence measurements

    Science.gov (United States)

    Akpinar, Erol; Reis, Dennys; Figueiredo Neto, Antonio Martins

    2013-03-01

    Lyotropic liquid crystals exhibiting nematic phases were obtained from the mixtures potassium laurate/alkali sulfate salts (M2SO4)/1-undecanol (UndeOH)/water and sodium dodecyl sulfate (SDS)/M2SO4/1-dodecanol (DDeOH)/water, where M2SO4 represents the alkali sulfate salts being Li2SO4, Na2SO4, K2SO4, Rb2SO4 or Cs2SO4. The birefringences measurements were performed via laser conoscopy. Our results indicated that cosmotropic and chaotropic behaviors of both ions and head groups are very important to obtain lyotropic biaxial nematic phase. To obtain the biaxial nematic phase, surfactant head group and ion present in lyotropic mixture have relatively opposite behavior, e.g. one more cosmotropic (more chaotropic) other less cosmotropic (less chaotropic) or vice versa.

  20. 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.; Becker, P.; Bohaty?, 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 ...

  1. Critical role of the sample preparation in experiments using piezoelectric actuators inducing uniaxial or biaxial strains

    OpenAIRE

    Butkovicova, D.; Marti, X.; Saidl, V.; Schmoranzerova-rozkotova, E.; Wadley, P.; Holy, V.; Nemec, P.

    2013-01-01

    We report on a systematic study of the stress transferred from an electromechanical piezo-stack into GaAs wafers under a wide variety of experimental conditions. We show that the strains in the semiconductor lattice, which were monitored in situ by means of X-ray diffraction, are strongly dependent on both the wafer thickness and on the selection of the glue which is used to bond the wafer to the piezoelectric actuator. We have identified an optimal set of parameters that re...

  2. Experimental investigation of strains in fabric under biaxial and shear forces.

    Science.gov (United States)

    Alley, V. L., Jr.; Faison, R. W.

    1972-01-01

    The paper defines the experimental phase of an objective to obtain the mechanical characteristics and coefficients required by the generalized form of Hooke's law for nylon-polyurethane-coated fabric. Test specimens were cylindrical fabric sleeves and were loaded in axial tension by an Instron, in hoop tension by pressurizing, and in shear by a torquing fixture. An extensive amount of strain data is included for a wide combination of the three membrane loads. The tests indicate highly nonlinear stress-strain characteristics of the fabric and a strong dependency on all three membrane loads.

  3. Near tip stress and strain fields for short elastic cracks

    Science.gov (United States)

    Soediono, A. H.; Kardomateas, G. A.; Carlson, R. L.

    1994-01-01

    Recent experimental fatigue crack growth studies have concluded an apparent anomalous behavior of short cracks. To investigate the reasons for this unexpected behavior, the present paper focuses on identifying the crack length circumstances under which the requirements for a single parameter (K(sub I) or delta K(sub I) if cyclic loading is considered) characterization are violated. Furthermore, an additional quantity, the T stress, as introduced by Rice, and the related biaxiality ratio, B, are calculated for several crack lengths and two configurations, the single-edge-cracked and the centrally-cracked specimen. It is postulated that a two-parameter characterization by K and T (or B) is needed for the adequate description of the stress and strain field around a short crack. To further verify the validity of this postulate, the influence of the third term of the Williams series on the stress, strain and displacement fields around the crack tip and in particular on the B parameter is also examined. It is found that the biaxiality ratio would be more negative if the third term effects are included in both geometries. The study is conducted using the finite element method with linearly elastic material and isoparametric elements and axial (mode I) loading. Moreover, it is clearly shown that it is not proper to postulate the crack size limits for 'short crack' behavior as a normalized ratio with the specimen width, a/w; it should instead be stated as an absolute, or normalized with respect to a small characteristic dimension such as the grain size. Finally, implications regarding the prediction of cyclic (fatigue) growth of short cracks are discussed.

  4. Ion-irradiation induced stress relaxation in metallic thin films and multilayers grown by ion beam sputtering

    International Nuclear Information System (INIS)

    The stress state of Mo layers in Ni/Mo multilayers was investigated and its evolution under ion beam irradiation was monitored using the 'sin2 ?' method. The growth stress in the Mo sub-layers was found to be consistent with a hydrostatic state of stress, accounting for the local deformations due to point defects induced during the sputter growth process. The hydrostatic stress is also responsible for a biaxial stress component appearing in the multilayer that is attached to the substrate, an additional stress component which is superimposed to the coherency stress developed due to epitaxial growth of the multilayers. Ion-irradiation of multilayers results in partial stress relaxation at low fluences, as the growth stress can be almost fully relaxed, while the coherency stresses remain unchanged. That is due to the system's state, the growth stress is far from thermodynamic equilibrium, the coherency stress is close-to-equilibrium. The employed method, combining X-ray diffraction strain analysis and ion irradiation-induced relaxation, in addition to identifying the chemical effects contribution, proved to be a unique tool for recognising and distinguishing stress contributions

  5. Stress echocardiography

    OpenAIRE

    Salustri, A.

    1993-01-01

    This thesis presents the initial experience on stress echocardiography done at the Department of Cardiology, University Hospital of Rotterdam. The main purposes of this research were: 1) to assess the safety and feasibility of stress echocardiography; 2) to evaluate the sensitivity and specificity of stress echocardiography for the detection of coronary artery disease; 3) to compare the results of stress echocardiography with those obtained at myocardial perfusion scintig...

  6. Adolescent Stress.

    Science.gov (United States)

    Van Oteghen, Sharon L.; Forrest, Marian

    1988-01-01

    In a survey of 68 students (grades 7-9) students identified level, causes, and means of dealing with stress. Findings suggest overall stress increases with grade level; students avoid drugs as a coping strategy; and they find ways to deal with stress that demonstrate maturity. (IAH)

  7. Stress, Inc.

    Science.gov (United States)

    Integrated Teaching and Learning Program,

    Students explore the physical and psychological effect of stress and tension on human beings. Concepts of stress and stress management are introduced. Students discover how perception serves to fuel a huge industry dedicated to minimizing risk and relieving stress. Students complete a writing activity focused on developing critical thinking skills. Note: The literacy activities for the Mechanics unit are based on physical themes that have broad application to our experience in the world — concepts of rhythm, balance, spin, gravity, levity, inertia, momentum, friction, stress and tension.

  8. 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...

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

    International Nuclear Information System (INIS)

    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. Above-bandgap optical properties of biaxially strained GeSn alloys grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Richard D’Costa, Vijay, E-mail: elevrd@nus.edu.sg; Wang, Wei; Zhou, Qian; Yeo, Yee-Chia, E-mail: eleyeoyc@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583 (Singapore); Soon Tok, Eng [Department of Physics, National University of Singapore, Singapore 117551 (Singapore)

    2014-01-13

    The complex dielectric function of biaxially strained Ge{sub 1?x}Sn{sub x} (0???x???0.17) alloys grown on Ge (100) has been determined by spectroscopic ellipsometry from 1.2 to 4.7?eV. The effect of substitutional Sn incorporation and the epitaxial strain on the energy transitions E{sub 1}, E{sub 1}?+??{sub 1}, E{sub 0}?, and E{sub 2} of GeSn alloys is investigated. Our results indicate that the strained GeSn alloys show Ge-like electronic bandstructure with all the transitions shifted downward due to the alloying of Sn. The strain dependence of E{sub 1} and E{sub 1}?+??{sub 1} transitions is explained using the deformation potential theory, and values of ?5.4?±?0.4?eV and 3.8?±?0.5?eV are obtained for the hydrostatic and shear deformation potentials, respectively.

  11. A Study in Three-Dimensional Chaotic Dynamics: Granular Flow and Transport in a Bi-Axial Spherical Tumbler

    CERN Document Server

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

    2014-01-01

    We study 3D chaotic dynamics through an analysis of transport in a granular flow in a half-full spherical tumbler rotated sequentially about two orthogonal axes (a bi-axial "blinking" tumbler). The flow is essentially quasi-2D in any vertical slice of the sphere during rotation about a single axis, and we provide an explicit exact solution to the model in this case. Hence, the cross-sectional flow can be represented by a twist map, allowing us to express the 3D flow as a linked twist map (LTM). We prove that if the rates of rotation about each axis are equal, then (in the absence of stochasticity) particle trajectories are restricted to 2D surfaces consisting of a portion of a hemispherical shell closed by a "cap"; if the rotation rates are unequal, then particles can leave the surface they start on and traverse a volume of the tumbler. The period-one structures of the governing LTM are examined in detail: analytical expressions are provided for the location of period-one curves, their extent into the bulk of...

  12. Growth of thin Al2O3 films on biaxially oriented polymer films by atomic layer deposition

    International Nuclear Information System (INIS)

    The effects of thin film nucleation and initial growth on roughness, chemistry and thermomechanical properties of polymer film surfaces were studied. Al2O3 was deposited onto commercial biaxially oriented polypropylene and polylactic acid films at 80 °C by using atomic layer deposition technique. Both substrates, especially the more hydrophobic polypropylene, showed initial growth through Al2O3 clusters. There was a faster deposition of Al2O3 on polylactic acid film than on polypropylene at the early stages of the Al2O3 deposition. There were also indications of chemical interactions between polylactic acid and trimethyl aluminum used as a precursor for Al2O3. Changes in the thermo-mechanical properties of the polymer surfaces with Al2O3 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: ? Growth of atomic layer deposited Al2O3 at 80 °C was studied on commercial films. ? Both substrate films showed early Al2O3 growth through clusters. ? Initial growth rate depends on the nature of the substrate film surface. ? There were indications of chemical interactions between substrate and practions between substrate and precursor. ? Film thickness and chemical interactions affect thermo-mechanical properties.

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

    Science.gov (United States)

    Fabián Molina, Gustavo; Cabral, Ricardo Juan; Mazzola, Ignacio; Brain Lascano, Laura; Frencken, Jo E

    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, 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/cm(2) for 30?s while setting (Group 2), and heated with LED lamp of 1400?mW/cm(2) 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 (? = 0.05). Heating the glass-ionomer cements with an LED curing light of 1400?mW/cm(2) 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. PMID:23841095

  14. 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.

  15. High JC YBCO films on biaxially textured Ni with oxide buffer layers deposited using evaporation and sputtering techniques

    International Nuclear Information System (INIS)

    Epitaxial buffer layers of CeO2 and yttria-stabilised ZrO2 (YSZ) have been deposited on biaxially textured nickel substrates using evaporation and rf sputtering. The buffer layers were characterised by XRD, SEM and optical microscopy. YBa2Cu3O7-? (YBCO) films were deposited by high pressure dc sputtering on CeO2/YSZ/CeO2 buffered substrates and the resulting superconducting properties were measured inductively. On exclusively evaporated buffers critical current densities of up to 0.6 MA/cm2 (77.3 K, H=0 T) were achieved. The buffer layers showed some cracks after YBCO deposition, which we considered to be responsible for the relatively low JC. In contrast buffer architectures with evaporated CeO2 followed by rf sputtering of YSZ and CeO2 remained completely free of cracks after YBCO deposition. Critical current densities between 1.5 and 2.6 MA/cm2 (77 K, H=0 T) in 400 nm thick YBCO films were obtained reproducibly. The critical temperatures TC ranged between 87 and 92 K and the typical width ?TC of the transition was 1.5 K

  16. Stress relief and texture formation in aluminium nitride by plasma immersion ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Gan, B K [Applied and Plasma Physics, School of Physics (A28), University of Sydney, New South Wales 2006 (Australia); Bilek, M M M [Applied and Plasma Physics, School of Physics (A28), University of Sydney, New South Wales 2006 (Australia); McKenzie, D R [Applied and Plasma Physics, School of Physics (A28), University of Sydney, New South Wales 2006 (Australia); Shi, Yang [Applied and Plasma Physics, School of Physics (A28), University of Sydney, New South Wales 2006 (Australia); Tompsett, D A [Applied and Plasma Physics, School of Physics (A28), University of Sydney, New South Wales 2006 (Australia); Taylor, M B [Department of Applied Physics, RMIT University, GPO Box 2476V, Melbourne 3001 (Australia); McCulloch, D G [Department of Applied Physics, RMIT University, GPO Box 2476V, Melbourne 3001 (Australia)

    2004-03-17

    The effect on the intrinsic stress in AlN films of applying pulsed bias during cathodic arc deposition has been studied. We find that the stress depends only on the pulse voltage-pulse frequency product, V f. The form of the dependence is well fitted by an exponential function whose parameters can be interpreted physically. The preferred orientation changes progressively with V f, from hexagonal crystallites having their <0001> direction in the plane of the film at low V f, to hexagonal crystallites having their <0001> direction normal to the plane of the film at high V f. The <0001> in-plane orientation may be consistent with energy minimization in a biaxial stress field whereas the <0001> normal orientation is consistent with the alignment of a channelling direction with the ion beam.

  17. Residual stresses

    International Nuclear Information System (INIS)

    The principal effect of unloading a material strained into the plastic range is to create a permanent set (plastic deformation), which if restricted somehow, gives rise to a system of self-balancing within the same member or reaction balanced by other members of the structure., known as residual stresses. These stresses stay there as locked-in stresses, in the body or a part of it in the absence of any external loading. Residual stresses are induced during hot-rolling and welding differential cooling, cold-forming and extruding: cold straightening and spot heating, fabrication and forced fitting of components constraining the structure to a particular geometry. The areas which cool more quickly develop residual compressive stresses, while the slower cooling areas develop residual tensile stresses, and a self-balancing or reaction balanced system of residual stresses is formed. The phenomenon of residual stresses is the most challenging in its application in surface modification techniques determining endurance mechanism against fracture and fatigue failures. This paper discusses the mechanism of residual stresses, that how the residual stresses are fanned and what their behavior is under the action of external forces. Such as in the case of a circular bar under limit torque, rectangular beam under limt moment, reclaiming of shafts welds and peening etc. (author)

  18. Stress–strain relations for hydrogels under multiaxial deformation

    DEFF Research Database (Denmark)

    Drozdov, Aleksey; Christiansen, Jesper de Claville

    2013-01-01

    Constitutive equations are derived for the elastic response of swollen elastomers and hydrogels under an arbitrary deformation with finite strains. An expression is developed for the free energy density of a polymer network based on the Flory concept of flexible chains with constrained junctions and solvent-dependent reference configuration. The importance of introduction of a reference configuration evolving under swelling is confirmed by the analysis of experimental data on nanocomposite hydrogels subjected to swelling and drying. Adjustable parameters in the stress–strain relations are found by fitting observations on swollen elastomers, chemical gels (linked by covalent bonds and sliding cross-links), and physical gels under uniaxial stretching, equi-biaxial tension, and pure shear. Good agreement is demonstrated between the observations and results of numerical simulation. A pronounced difference is revealed between the effect of solvent content on elastic moduli of chemical and physical gels.

  19. Biaxial incremental homeostatic elastic moduli of coronary artery: two-layer model.

    Science.gov (United States)

    Lu, Xiao; Pandit, Aditya; Kassab, Ghassan S

    2004-10-01

    The detailed mechanical properties of various layers of the coronary artery are important for understanding the function of the vessel. The present article is focused on the determination of the incremental modulus in different layers and directions in the neighborhood of the in vivo state. The incremental modulus can be defined for any material subjected to a large deformation if small perturbations in strain lead to small perturbations of stresses in a linear fashion. This analysis was applied to the porcine coronary artery, which was treated as a two-layered structure consisting of an inner intima-media layer and an outer adventitia layer. We adopted a theory based on small-perturbation experiments at homeostatic conditions for determination of incremental moduli in circumferential, axial, and cross directions in the two layers. The experiments were based on inflation and axial stretch. We demonstrate that under homeostatic conditions the incremental moduli are layer- and direction dependent. The incremental modulus is highest in the circumferential direction. Furthermore, in the circumferential direction, the media is stiffer than the whole wall, which is stiffer than the adventitia. In the axial direction, the adventitia is stiffer than the intact wall, which is stiffer than the media. Hence, the coronary artery must be treated as a composite, nonisotropic body. The data acquire physiological relevance in relation to coronary artery health and disease. PMID:15371266

  20. Mechanically reinforced and biaxially textured Ni alloys composite substrates for coated conductors

    International Nuclear Information System (INIS)

    Key requirements for the substrates employed in coated conductors are using magnetic reduced and strengthening materials. In this work, Ni-based alloy composite tapes were designed and prepared in order to meet such needs through a hybrid route. A novel multi-layer of composite tapes was obtained by sintering two pieces of Ni-5at.%W (out layers) connected with Ni-12at.%W mixture powder together using sparking plasma sintering (SPS) technology. The high tungsten contents mixture powder after sintering not only played a role as a joint layer, but also performed high strength and reduced ferromagnetism as an inner layer at the same time. The sharp cube texture was obtained in the composite tapes after the optimized cold rolling and recrystallization. The FWHM values of (1 1 1) Phi-scans and (0 0 2) rocking curves of these tapes were around 9.45oand 5.48o, respectively, measured by X-rays. Extremely, the yield stress of this composite substrate exceeds 320 MPa, the magnetization of the composite substrate being reduced to 10.9 emu/g at 77 K, only 41% in comparison with commercial Ni5W substrate

  1. Bone Stress

    Science.gov (United States)

    The Exploratorium

    2011-12-07

    In this optics activity, learners examine how polarized light can reveal stress patterns in clear plastic. Learners place a fork between two pieces of polarizing material and induce stress by squeezing the tines together. Learners will observe the colored stress pattern in the image of the plastic that is projected onto a screen using an overhead projector. Learners rotate one of the polarizing filters to explore which orientations give the most dramatic color effects. This activity can be related to bones, as bones develop stress patterns from the loads imposed upon them every day.

  2. "STRESS MANAGEMENT”

    Directory of Open Access Journals (Sweden)

    Amit Kumar

    2014-06-01

    Full Text Available Initially my studied in depth about what is stress and stress management, we visited different colleges and approached different teachers to find out what are the various questions that can be put in our questionnaire. Now our next job was to pen down the questions we could ask teachers which should not be too harsh and direct that makes teachers uncomfortable to cooperate. After making questionnaire the next hurdle that came was what if teachers didn't knew whether they were stressed or what if they refused even though they were stressed.

  3. Effect of light sources and curing mode techniques on sorption, solubility and biaxial flexural strength of a composite resin

    Scientific Electronic Library Online (English)

    Andreia Assis, Carvalho; Francine do Couto Lima, Moreira; Rodrigo Borges, Fonseca; Carlos José, Soares; Eduardo Batista, Franco; João Batista de, Souza; Lawrence Gonzaga, Lopes.

    2012-04-01

    Full Text Available SciELO Brazil | Language: English Abstract in english Adequate polymerization plays an important role on the longevity of the composite resin restorations. OBJECTIVES: The aim of this study was to evaluate the effect of light-curing units, curing mode techniques and storage media on sorption, solubility and biaxial flexural strength (BFS) of a composit [...] e resin. MATERIAL AND METHODS: Two hundred and forty specimens were made of one composite resin (Esthet-X) in a stainless steel mold (2 mm x 8 mm Ø), and divided into 24 groups (n=10) established according to the 4 study factors: light-curing units: quartz tungsten halogen (QTH) lamp and light-emitting diodes (LED); energy densities: 16 J/cm² and 20 J/cm²; curing modes: conventional (CM) and pulse-delay (PD); and permeants: deionized water and 75% ethanol for 28 days. Sorption and solubility tests were performed according to ISO 4049:2000 specifications. All specimens were then tested for BFS according to ASTM F394-78 specification. Data were analyzed by three-way ANOVA followed by Tukey, Kruskal-Wallis and Mann-Whitney tests (?=0.05). RESULTS: In general, no significant differences were found regarding sorption, solubility or BFS means for the light-curing units and curing modes (p>0.05). Only LED unit using 16 J/cm² and PD using 10 s produced higher sorption and solubility values than QTH. Otherwise, using CM (16 J/cm²), LED produced lower values of BFS than QTH (p

  4. Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl6

    Science.gov (United States)

    Pilania, G.; Uberuaga, B. P.

    2015-03-01

    Here, we investigate the electronic structure, energetics of cation ordering, and effect of biaxial strain on double perovskite CsRbCaZnCl6 using first-principles calculations based on density functional theory. The two constituents (i.e., CsCaCl3 and RbZnCl3) forming the double perovskite exhibit a stark contrast. While CsCaCl3 is known to exist in a cubic perovskite structure and does not show any epitaxial strain induced phase transitions within an experimentally accessible range of compressive strains, RbZnCl3 is thermodynamically unstable in the perovskite phase and exhibits ultra-sensitive response at small epitaxial strains if constrained in the perovskite phase. We show that combining the two compositions in a double perovskite structure not only improves overall stability but also the strain-polarization coupling of the material. Our calculations predict a ground state with P4/nmm space group for the double perovskite, where A-site cations (i.e., Cs and Rb) are layer-ordered and B-site cations (i.e., Ca and Zn) prefer a rocksalt type ordering. The electronic structure and bandgap in this system are shown to be quite sensitive to the B-site cation ordering and is minimally affected by the ordering of A-site cations. We find that at experimentally accessible compressive strains CsRbCaZnCl6 can be phase transformed from its paraelectric ground state to an antiferroelectric state, where Zn atoms contribute predominantly to the polarization. Furthermore, both energy difference and activation barrier for a transformation between this antiferroelectric state and the corresponding ferroelectric configuration are predicted to be small. The computational approach presented here opens a new pathway towards a rational design of novel double perovskites with improved strain response and functionalities.

  5. 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.

  6. Nuclear stress test

    Science.gov (United States)

    ... Persantine stress test; Thallium stress test; Stress test - nuclear; Adenosine stress test; Regadenoson stress test ... Thallium stress test is a nuclear imaging method that shows how well blood flows into the heart muscle, both at rest and during activity.

  7. Low Pressure Hexamethyldisiloxane (HMDSO)/Nitrogen Plasma Treatment on the Wettability and Surface Free Energy of Biaxial-Oriented Polypropylene (BOPP) Films

    Science.gov (United States)

    Mortazavi, S. Hamideh; Ghoranneviss, Mahmood; Sari, A. H.

    2011-02-01

    In this paper the influence of DC glow discharge HMDSO-N2 plasma on wettability and surface properties of Biaxial-oriented polypropylene (BOPP) polymeric surfaces, has been investigated. The effects of plasma exposure time and HMDSO percent on the surface energy and wettability of the BOPP films were characterized using Fourier transform infrared spectroscopy (FTIR), Atomic force microscopy (AFM) and contact angle measurement. A clear change in the surface energy of BOPP films due to plasma treatment was observed. In this work we report changing surface properties of BOPP films instead of plasma treatment time and HMDSO ratios.

  8. Job Stress

    Science.gov (United States)

    ... University of Utah study found that as stressed workers get older, their blood pressure increases above normal levels. Interestingly, many of the study's over-60 workers reported that they did not feel upset or ...

  9. Stress hysteresis and mechanical properties of plasma-enhanced chemical vapor deposited dielectric films

    Science.gov (United States)

    Thurn, Jeremy; Cook, Robert F.; Kamarajugadda, Mallika; Bozeman, Steven P.; Stearns, Laura C.

    2004-02-01

    A comprehensive survey is described of the responses of three plasma-enhanced chemical vapor deposited dielectric film systems to thermal cycling and indentation contact. All three films—silicon oxide, silicon nitride, and silicon oxy-nitride—exhibited significant nonequilibrium permanent changes in film stress on thermal cycling or annealing. The linear relationship between stress and temperature changed after the films were annealed at 300 °C, representing a structural alteration in the film reflecting a change in coefficient of thermal expansion or biaxial modulus. A double-substrate method was used to deduce both thermoelastic properties before and after the anneal of selected films and the results were compared with the modulus deconvoluted from small-scale depth-sensing indentation experiments (nanoindentation). Rutherford backscattering spectrometry and hydrogen forward scattering were used to deduce the composition of the films and it was found that all the films contained significant amounts of hydrogen.

  10. Stress hysteresis and mechanical properties of plasma-enhanced chemical vapor deposited dielectric films

    International Nuclear Information System (INIS)

    A comprehensive survey is described of the responses of three plasma-enhanced chemical vapor deposited dielectric film systems to thermal cycling and indentation contact. All three films - silicon oxide, silicon nitride, and silicon oxy-nitride - exhibited significant nonequilibrium permanent changes in film stress on thermal cycling or annealing. The linear relationship between stress and temperature changed after the films were annealed at 300 deg. C, representing a structural alteration in the film reflecting a change in coefficient of thermal expansion or biaxial modulus. A double-substrate method was used to deduce both thermoelastic properties before and after the anneal of selected films and the results were compared with the modulus deconvoluted from small-scale depth-sensing indentation experiments (nanoindentation). Rutherford backscattering spectrometry and hydrogen forward scattering were used to deduce the composition of the films and it was found that all the films contained significant amounts of hydrogen

  11. 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

    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 to the flow in the non-linear flow regime. This has allowed highly elastic measurements within the limit of pure orientational stress, as the time of the flow was considerably smaller than the Rouse time. A Doi-Edwards [J. Chem. Soc., Faraday Trans. 2 74, 1818-1832 (1978)] type of constitutive model 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

  12. Soapy Stress

    Science.gov (United States)

    Integrated Teaching and Learning Program,

    To experience the three types of material stress related to rocks — tensional, compressional and shear — students break bars of soap using only their hands. They apply force created by the muscles in their own hands to put pressure on the soap, a model for the larger scale, real-world phenomena that forms, shapes and moves the rocks of our planet. They also learn the real-life implications of understanding stress in rocks, both for predicting natural hazards and building safe structures.

  13. Multi-mode technique for the determination of the biaxial Y2SiO5 permittivity tensor from 300 to 6 Kelvin

    CERN Document Server

    Carvalho, N C; Krupka, J; Tobar, M E

    2015-01-01

    The Y2SiO5 (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 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 a new multi-mode technique, which uses simultaneous measurement of low order Whispery Gallery Modes. Knowledge of the permittivity tensor offers new important data, es...

  14. Residual stress and the effect of implanted argon in films of zirconium nitride made by physical vapor deposition

    International Nuclear Information System (INIS)

    Zirconium nitride films made by reactive cathodic arc evaporation at high bias have been dual energy ion implanted with argon. It is found that the x-ray elastic constants of the unimplanted films differ from those measured under simple biaxial compressive elastic stress conditions. The effect of 1% argon implantation is to reduce both the lattice parameters and the compressive residual stress. It is considered that the argon resides on substitutional lattice sites following a softening of the implanted layers caused by the energy accompanying the implantation process. As the amount of argon implanted is increased (6% or 12%), the lattice continues to contract, but less rapidly, and the residual stress is hardly affected. It is suggested that the lattice softening continues and is accompanied by precipitation of the argon as bubbles

  15. 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.

    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/?2/0/-?2]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 of different thickness between the thin (2-plies) and the thick (4-plies) layers. Results are presented in terms of S–N curves for the initiation of the first cracks, crack density evolution, stiffness degradation and Paris-like curves for the crack propagation phase. The values of the off-axis angle ? 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 stress states. © 2014 Elsevier Ltd. All rights reserved.

  16. Hypervelocity Impact of Unstressed and Stressed Titanium in a Whipple Configuration in Support of the Orion Crew Exploration Vehicle Service Module Propellant Tanks

    Science.gov (United States)

    Nahra, Henry K.; Christiansen, Eric; Piekutowski, Andrew; Lyons, Frankel; Keddy, Christopher; Salem, Jonathan; Miller, Joshua; Bohl, William; Poormon, Kevin; Greene, Nathanel; Rodriquez, Karen

    2010-01-01

    Hypervelocity impacts were performed on six unstressed and six stressed titanium coupons with aluminium shielding in order to assess the effects of the partial penetration damage on the post impact micromechanical properties of titanium and on the residual strength after impact. This work is performed in support of the definition of the penetration criteria of the propellant tanks surfaces for the service module of the crew exploration vehicle where such a criterion is based on testing and analyses rather than on historical precedence. The objective of this work is to assess the effects of applied biaxial stress on the damage dynamics and morphology. The crater statistics revealed minute differences between stressed and unstressed coupon damage. The post impact residual stress analyses showed that the titanium strength properties were generally unchanged for the unstressed coupons when compared with undamaged titanium. However, high localized strains were shown near the craters during the tensile tests.

  17. Stress and Mood

    Science.gov (United States)

    Home » Stress & Mood Stress & Mood Many people who go back to smoking do it when they are feeling down or stressed out. This ... story: Time Out Times 10 >> share What Causes Stress? Read full story: What Causes Stress? >> share The ...

  18. Welding stresses

    International Nuclear Information System (INIS)

    The aim is to show how internal stresses are generated and to fix the orders of magnitude. A realistic case, the vertical welding of thick plates free to move one against the other, is described and the deformations and stresses are analyzed. The mathematical model UEDA, which accounts for the elastic modulus, the yield strength and the expansion coefficient of the metal with temperature, is presented. The hypotheses and results given apply only to the instantaneous welding of a welded plate and to a plate welded by a moving electrode

  19. Biaxially textured composite substrates

    Science.gov (United States)

    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.

  20. Stress analysis of two-dimensional cellular materials with thick cell struts

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Do Hyung; Kim, Han Sung; Kim, Young Ho [Yonsei University, Wonju (Korea, Republic of); Kim, Yoon Hyuk [Kyunghee University, Yongin (Korea, Republic of); Al-Hassani, S.T.S. [University of Manchester, Manchester (United Kingdom)

    2008-05-15

    Finite element analyses (FEA) were performed to thoroughly validate the collapse criteria of cellular materials presented in our previous companion paper. The maximum stress (von-Mises stress) on the cell strut surface and the plastic collapse stress were computed for two-dimensional (2D) cellular materials with thick cell struts. The results from the FEA were compared with those from theoretical criteria of authors. The FEA results were in good agreement with the theoretical results. The results indicate that when bending moment, axial and shear forces are considered, the maximum stress on the strut surface gives significantly different values in the tensile and compressive parts of the cell wall as well as in the two loading directions. Therefore, for the initial yielding of ductile cellular materials and the fracture of brittle cellular materials, in which the maximum stress on the strut surface is evaluated, it is necessary to consider not only the bending moment but also axial and shear forces. In addition, this study shows that for regular cellular materials with the identical strut geometry for all struts, the initial yielding and the plastic collapse under a biaxial state of stress occur not only in the inclined cell struts but also in the vertical struts. These FEA results support the theoretical conclusion of our previous companion paper that the anisotropic 2D cellular material has a truncated yield surface not only on the compressive quadrant but also on the tensile quadrant

  1. Stress analysis of two-dimensional cellular materials with thick cell struts

    International Nuclear Information System (INIS)

    Finite element analyses (FEA) were performed to thoroughly validate the collapse criteria of cellular materials presented in our previous companion paper. The maximum stress (von-Mises stress) on the cell strut surface and the plastic collapse stress were computed for two-dimensional (2D) cellular materials with thick cell struts. The results from the FEA were compared with those from theoretical criteria of authors. The FEA results were in good agreement with the theoretical results. The results indicate that when bending moment, axial and shear forces are considered, the maximum stress on the strut surface gives significantly different values in the tensile and compressive parts of the cell wall as well as in the two loading directions. Therefore, for the initial yielding of ductile cellular materials and the fracture of brittle cellular materials, in which the maximum stress on the strut surface is evaluated, it is necessary to consider not only the bending moment but also axial and shear forces. In addition, this study shows that for regular cellular materials with the identical strut geometry for all struts, the initial yielding and the plastic collapse under a biaxial state of stress occur not only in the inclined cell struts but also in the vertical struts. These FEA results support the theoretical conclusion of our previous companion paper that the anisotropic 2D cellular material has a truncated yield surface not only on the compressive quadrant but also on t on the compressive quadrant but also on the tensile quadrant

  2. Investigations of the effects of the state of stress on fracture characteristics

    International Nuclear Information System (INIS)

    In this paper investigations have been made whether a biaxial load increases the stress stateover the plain strain and whether consequently a decrease of the critical fracture toughness and a shift of the temperatures Tsub(g)sub(y) and Tsub(s) results which characterise the fracture behaviour of steel. In order to answer these questions the tests were made which induced due to their geometry an additional nominal stress parallel to the crack front inspite of uni-axial loading. The results were compared with those from specimen without an additional nominal stress and having in their cross section under same test conditions nearly the same plain strain. The fracture toughness of both specimen types were compared at temperatures between 142 K and 252 K and correlated to other material-characterising values. The tests were completed by stress analysis and by comparing the crack opening displacement. Due to the additional stress, Tsub(g)sub(y) was found to be 20 K higher than for the reference specimen. The fracture toughness decreases significantly in certain temperature ranges. The plastic stress concentration factor was comparatively higher and the remaining plastic crack opening decreases up to 25%. (orig./IHOE)

  3. Stress Analysis

    DEFF Research Database (Denmark)

    Burcharth, Hans F.

    1988-01-01

    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)

  4. 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.

  5. Bi-axial magnetic orientation in a twinned ErBa{sub 2}Cu{sub 3}O{sub y} superconductor by controlling grain size

    Energy Technology Data Exchange (ETDEWEB)

    Horii, S; Tanoue, T; Yamaki, M; Maeda, T [Department of Environmental Systems Engineering, Kochi University of Technology, Tosa-Yamada, Kami-shi, Kochi 782-8502 (Japan); Shimoyama, J, E-mail: horii.shigeru@kochi-tech.ac.jp [JST-TRIP, Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan)

    2011-05-15

    Bi-axial magnetic orientation in ErBa{sub 2}Cu{sub 3}O{sub y} (Er123) superconductor with a twinned microstructure was demonstrated. A ball-milling process effectively improved the degree of the in-plane and c-axis orientation of Er123 powder samples oriented in a modulated rotating magnetic field of 10 T. From the relationship between the particle size and the degree of orientation, it is concluded that pulverization induced the appearance of the in-plane magnetic anisotropy of Er123 grains through inhomogenization of two different types of domains in their grains. The present study presents a production technique of RE123 bulk magnets and coated conductors without epitaxy technology.

  6. Design and calibration of a bi-axial extended octagonal ring transducer system for the measurement of tractor-implement forces

    Directory of Open Access Journals (Sweden)

    Khan J.

    2007-02-01

    Full Text Available A bi-axial extended octagonal ring (EOR transducer system for the measurement of tractor-implement forces was designed for a category II and III MB Trac 1300 tractor. The EOR transducers and a gauged top link were calibrated and the Sensitivity, Cross-Sensitivity, Hysteresis, Linearity and Repeatability were found. The system was tested for 80kN applied coincident load and 60kN perpendicular load. No lateral forces or moment in the plane of the two forces was considered. The results of the calibration tests of the system showed its workability. The system could best be used for the measurement of draught (horizontal and vertical forces where heavy implements are attached with the tractor.

  7. 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.

  8. The biaxial nonlinear crystal BiB?O? 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 BiB?O? (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 ?-BaB?O? (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

  9. 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

    Manti?, 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...

  10. Stress analyses of flat plates with attached nozzles. Vol. 2: Experimental stress analyses of a flat plate with one nozzle attached

    International Nuclear Information System (INIS)

    Vol. 1 of this report compares experimental results with theoretical stress distributions for a flat plate with one nozzle configuration and for a flat plate with two closely spaced nozzles attached. This volume contains the complete test results for a flat plate with one nozzle attached that was subjected to 1:1 and 1:2 biaxial planar loadings on the plate, to a thrust loading on the nozzle, and to a moment loading on the nozzle. The plate tested was 36 x 36 x 0.375 in., and the attached nozzle had an outer dia of 2.625 in. and a 0.250-in.-thick wall. The nozzle was located in the center of the plate and was considered to be free of weld distortions and irregularities in the junction area. (U.S.)

  11. Effect of biaxial strain on half-metallicity of transition metal alloyed zinc-blende ZnO and GaAs: a first-principles study

    International Nuclear Information System (INIS)

    The electronic structure, magnetic and half-metallic properties of transitional metal (TM)-alloyed zinc-blende ZnO and GaAs (TM = Cr, Mn, Fe, Co, Ni) thin films with biaxial strains on the (0 0 1) plane are studied by density functional theory and beyond. Here, we focus on two simple layer-by-layer delta doping structures with the TM substituting along the (1 0 0) planes (type-I) and (0 0 1) planes (type-II). We find that the Fe-, Co- and Ni-alloyed GaAs, Mn- and Fe-alloyed ZnO, and Co-alloyed ZnO(II) show antiferromagnetic (AFM) states, while Ni-alloyed ZnO(I) and Cr-alloyed GaAs show ferromagnetic (FM) coupling independent of the biaxial strain within 25% along the (0 0 1) plane. For the systems of Cr-alloyed ZnO, Co-alloyed ZnO(I), Ni-alloyed ZnO(II) and Mn-alloyed GaAs(I, II), the strain from the substrate will induce a phase transition from AFM to FM states. The Co-alloyed ZnO(I), Ni-alloyed ZnO(I, II) and Cr-alloyed GaAs(I, II) systems are demonstrated to be half-metallic from the generalized gradient approximation (GGA) calculations. The Cr-alloyed ZnO and Mn-alloyed GaAs systems also show robust half-metallicity with a large spin-flip gap by a GGA + U description, although their half-metallicity disappears with the standard GGA description.

  12. Stress and Skin

    Science.gov (United States)

    ... they feel emotionally. On a microscopic level, stress reduction can decrease the release of pro-inflammatory stress ... substantially reduce patients' stress and improve their skin, hair and nail conditions. However, if stress is clearly ...

  13. 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)

  14. Atomic-level stress and induced growth of wurtzite zinc oxide using molecular dynamics simulation

    Science.gov (United States)

    Hong, Zheng-Han; Fang, Te-Hua; Hwang, Shun-Fa

    2011-12-01

    Molecular dynamics is used to simulate the film growth process of zinc oxide (ZnO) deposited on a ZnO substrate. In the work, the Buckingham-type interatomic potential is modelled to describe the interaction of Zn-O atoms. The effects of incident energy and substrate temperature on the layer coverage function, radial distribution function and residual stress are investigated. Results show that the crystal growth of the deposition film is a symmetric wurtzite lattice along the [0?0?0?1] direction due to charge transformation. Epitaxial-like growth only occurs at very low incident energies, while the intermixing process could start from an incident energy of 3 eV. The average stress of the Zn layer is a compressive stress that is close to zero. However, the average mean biaxial stress and the normal stress of the O layer are -4.49 GPa and -3.07 GPa, respectively. The simulation results are compared with experimental results available in the literature.

  15. 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

  16. A Method to Estimate Residual Stress in Austenitic Stainless Steel Using a Microindentation Test

    Science.gov (United States)

    Yonezu, Akio; Kusano, Ryota; Hiyoshi, Tomohiro; Chen, Xi

    2015-01-01

    This study proposed a method to evaluate the residual stress and plastic strain of an austenitic stainless steel using a microindentation test. The austenitic stainless steel SUS316L obeys the Ludwick's work hardening law and is subjected to in-plane equi-biaxial residual stress. A numerical experiment with the finite element method (FEM) was carried out to simulate an indentation test for SUS316L having various plastic strains (pre-strains) and residual stresses. It was found that the indentation force increased with increasing pre-strain as well as with compressive residual stress. Next, a parametric FEM study by changing both residual stress ?res and pre-strain ?pre was conducted to deduce the relationship between the indentation curve and the parameters ?pre and ?res (which were employed for the FEM study). This relationship can be expressed by a dimensionless function with simple formulae. Thus, the present method can estimate both ?pre and ?res, when a single indentation test is applied to SUS316L.

  17. Atomic-level stress and induced growth of wurtzite zinc oxide using molecular dynamics simulation

    International Nuclear Information System (INIS)

    Molecular dynamics is used to simulate the film growth process of zinc oxide (ZnO) deposited on a ZnO substrate. In the work, the Buckingham-type interatomic potential is modelled to describe the interaction of Zn-O atoms. The effects of incident energy and substrate temperature on the layer coverage function, radial distribution function and residual stress are investigated. Results show that the crystal growth of the deposition film is a symmetric wurtzite lattice along the [0?0?0?1] direction due to charge transformation. Epitaxial-like growth only occurs at very low incident energies, while the intermixing process could start from an incident energy of 3 eV. The average stress of the Zn layer is a compressive stress that is close to zero. However, the average mean biaxial stress and the normal stress of the O layer are -4.49 GPa and -3.07 GPa, respectively. The simulation results are compared with experimental results available in the literature. (paper)

  18. Effects of texture of zirconium alloy and multi-axial stress on iodine SCC susceptibility

    International Nuclear Information System (INIS)

    An analytical model of iodine stress corrosion cracking (SCC) of hexagonal close packed metals is developed. The SCC susceptibility is represented in the model by the elastic strain energy in the single crystals with tensile strain toward the axis of the crystal. The model incorporates the effect of crystallographic textures and multi-axial stress states. The SCC susceptibilities of the Zr and Zr alloy fuel claddings with three different textures are calculated based on the model. It is found that the stress for the tangential tensile loading of cladding is about 40% of that for longitudinal tensile loading with the same SCC susceptibility. Measurements are made on the number of microcracks on the inner surface of the Zircaloy-2 fuel claddings. These cracks are produced during the iodine SCC tests performed at 3500C under the biaxial stress state with a constant Mises' effective stress. The SCC susceptibility obtained by the proposed model was found to agree with the experimental results. The SCC susceptibility for the ?-zirconium single crystal, as calculated by the model, is also shown to be in good agreement with experimental results. (author)

  19. Effects of texture of zirconium alloy and multi-axial stress on iodine SCC susceptibility

    International Nuclear Information System (INIS)

    An analytical model of iodine stress corrosion cracking (SCC) of hexagonal close packed metals is developed. The SCC susceptibility is represented in the model by the elastic strain energy in the single crystals with tensile strain toward the axis of the crystal. The model incorporates the effect of crystallographic textures and multi-axial stress states. The SCC susceptibilities of the zirconium and zirconium alloy fuel claddings with three different textures are calculated based on the model. It is found that the stress for the tangential tensile loading of cladding is about 40% of that for longitudinal tensile loading with the same SCC susceptibility. Measurements are made on the number of microcracks on the inner surface of the Zircaloy-2 fuel claddings. These cracks are produced during the iodine SCC tests performed at 350 deg. C under the biaxial stress state with a constant Mises' effective stress. The SCC susceptibility obtained by the proposed model was found to agree with the experimental results. The SCC susceptibility for the ?-zirconium single crystal, as calculated by the model, is also shown to be in good agreement with experimental results. (author)

  20. Effect of laser shock peening on residual stress and fatigue life of clad 2024 aluminium sheet containing scribe defects

    International Nuclear Information System (INIS)

    Highlights: ? Effect of laser peen intensity on local residual stress fields in 2024 aluminium. ? Peening induces significant changes in surface topography and local hardness. ? Residual stress at peen spot centre in tension, spot overlap in compression. ? Notched fatigue lives increased; crack morphology correlated to residual stress field. ? 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 ?m deep scribes, and slight improvement for samples with 150 ?m scribes. Use of the residual stress intensity Kresid approach to calculate fatigue life improvement arising from peening was unsuccessful at predicting the relative effet predicting the relative effects of the different peening treatments. Possible reasons for this are explored.

  1. 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 2? 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 the residual stress in the electrolyte layer and thus to the involved damage mechanisms.

  2. Oxidative stress

    Directory of Open Access Journals (Sweden)

    Stevanovi? 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

  3. Modeling of delayed strains of concrete under biaxial loadings. Application to the reactor containment of nuclear power plants

    International Nuclear Information System (INIS)

    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)

  4. Identification of a Visco-Elastic Model for PET Near Tg Based on Uni and Biaxial Results

    OpenAIRE

    Luo, Y. M.; Chevalier, L.; Monteiro, E.

    2011-01-01

    The mechanical response of Polyethylene Terephthalate (PET) in elongation is strongly dependent on temperature, strain and strain rate. Near the glass transition temperature Tg, the stress-strain curve presents a strain softening effect vs strain rate but a strain hardening effect vs strain under conditions of large deformations. The main goal of this work is to propose a viscoelastic model to predict the PET behaviour when subjected to large deformations and to determine the material propert...

  5. Temperature dependence of biaxial strain and its influence on phonon and band gap of GaN thin film

    International Nuclear Information System (INIS)

    Hexagonal GaN epilayer grown on sapphire substrate by metal organic chemical vapour deposition (MOCVD) is studied using Raman scattering and photoluminescence in a temperature range from 100 K to 873 K. The model of strain (stress) induced by the different lattice parameters and thermal coefficients of epilayer and substrate as a function of temperature is set up. The frequency and the linewidth of E2high mode in a GaN layer are modelled by a theory with considering the thermal expansion of the lattice, a symmetric decay of the optical phonons, and the strain (stress) in the layer. The temperature-dependent energy shift of free exciton A is determined by using Varshni empirical relation, and the effect of strain (stress) is also investigated. We find that the strain in the film leads to a decreasing shift of the phonon frequency and an about 10meV-increasing shift of the energy in a temperature range from 100 K to 823 K

  6. Temperature dependence of biaxial strain and its influence on phonon and band gap of GaN thin film

    Science.gov (United States)

    Xu, Hong-Yan; Jian, Ao-Qun; Xue, Chen-Yang; Chen, Yang; Zhang, Bin-Zhen; Zhang, Wen-Dong; Zhang, Zhi-Guo; Feng, Zhen

    2008-06-01

    Hexagonal GaN epilayer grown on sapphire substrate by metal organic chemical vapour deposition (MOCVD) is studied using Raman scattering and photoluminescence in a temperature range from 100 K to 873 K. The model of strain (stress) induced by the different lattice parameters and thermal coefficients of epilayer and substrate as a function of temperature is set up. The frequency and the linewidth of E2high mode in a GaN layer are modelled by a theory with considering the thermal expansion of the lattice, a symmetric decay of the optical phonons, and the strain (stress) in the layer. The temperature-dependent energy shift of free exciton A is determined by using Varshni empirical relation, and the effect of strain (stress) is also investigated. We find that the strain in the film leads to a decreasing shift of the phonon frequency and an about 10meV-increasing shift of the energy in a temperature range from 100 K to 823 K.

  7. 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.

  8. 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)

  9. Analysis of stresses in finite anisotropic panels with centrally located cutouts

    Science.gov (United States)

    Britt, Vicki O.

    1992-01-01

    A method for analyzing biaxial- and shear-loaded anisotropic rectangular panels with centrally located circular and elliptical cutouts is presented in the present paper. The method is based on Lekhnitskii's complex variable equations of plane elastostatics combined with a boundary collocation method and a Laurent series approximation. Results are presented for anisotropic panels with elliptical cutouts and subjected to combined shear and compression loading. The effects on the stress field of panel aspect ratio, anisotropy, cutout size, and cutout orientation are addressed. Angle-ply laminates, unidirectional off-axis laminates, and ((+ or - 45/0/90)(sub 3))s, ((+ or - 45/0(sub 2))(sub 3))s, and ((+ or - 45/90(sub 2))(sub 3))s laminates are examined.

  10. Phase transition and magnetic properties of a bond-diluted mixed spin-1 and spin1/2 Ising model with the uniaxial and biaxial single-ion anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Belmamoun, Y; Kerouad, M [LPMMS, Department of Physics, Faculty of Sciences, University Moulay Ismail, BP 11201, Zitoune, Meknes (Morocco)], E-mail: kerouad@fs-umi.ac.ma

    2008-02-15

    The effective-field theory with a probability distribution technique that accounts for the self-spin correlation functions is used to study the phase diagrams and magnetic properties of a bond-diluted mixed spin1/2 and spin-1 Ising model with the uniaxial and biaxial single-ion anisotropy on a simple cubic structure. It is found that the phase diagrams of the system can exhibit re-entrant phenomena for certain values of the concentration p and uniaxial and biaxial single-ion anisotropy, D{sub 0}/J, D{sub x}/J and D{sub y}/J. We have also studied the effect of these parameters on the existence of the tricritical behavior.

  11. Phase transition and magnetic properties of a bond-diluted mixed spin-1 and spin1/2 Ising model with the uniaxial and biaxial single-ion anisotropy

    International Nuclear Information System (INIS)

    The effective-field theory with a probability distribution technique that accounts for the self-spin correlation functions is used to study the phase diagrams and magnetic properties of a bond-diluted mixed spin1/2 and spin-1 Ising model with the uniaxial and biaxial single-ion anisotropy on a simple cubic structure. It is found that the phase diagrams of the system can exhibit re-entrant phenomena for certain values of the concentration p and uniaxial and biaxial single-ion anisotropy, D0/J, Dx/J and Dy/J. We have also studied the effect of these parameters on the existence of the tricritical behavior

  12. Association of catastrophic biaxial fracture of the proximal sesamoid bones with bony changes of the metacarpophalangeal joint identified by standing magnetic resonance imaging in cadaveric forelimbs of Thoroughbred racehorses.

    Science.gov (United States)

    Peloso, John G; Vogler Iii, James B; Cohen, Noah D; Marquis, Patricia; Hilt, Lynn

    2015-03-15

    Objective-To compare bony changes in the metacarpophalangeal joint (MCPJ) of racehorses with (cases) and without (controls) biaxial proximal sesamoid bone (PSB) fracture as determined by 2 grading scales applied to images of cadaveric forelimbs obtained by means of standing MRI (sMRI). Design-Case-control study. Sample-Forelimbs from 74 Thoroughbred racehorses (21 cases and 53 controls) that were euthanized at a Florida racetrack. Procedures-Both forelimbs were harvested from cases and controls. Each forelimb underwent sMRI to obtain images of the MCPJ. Two grading scales were described and used for image evaluation; one assessed the density of the PSBs, and the other assessed the integrity of the subchondral bone (SCB) plate at the distopalmar aspect of the third metacarpal bone (MC3). Logistic regression was used to compare the grades between case and control limbs. Results-Biaxial PSB fracture was associated with a total PSB grade (sum of lateral and medial PSB grades) ? 5 for the fractured limb, total MC3 SCB grade (sum of lateral and medial MC3 SCB grades) ? 5 for the contralateral limb, and the presence of orthopedic disease in the contralateral MC3. Conclusions and Clinical Relevance-For cases with biaxial PSB fracture, the density of the PSBs in the affected limb was greater and the MC3 of the contralateral limb was more likely to have orthopedic disease, compared with those for controls. Further evaluation of sMRI as a screening tool for identification of racehorses at risk of biaxial PSB fracture is warranted. (J Am Vet Med Assoc 2015;246:661-673). PMID:25719849

  13. Generalized Stress Concentration Factors

    OpenAIRE

    Segev, Reuven

    2006-01-01

    The classical stress concentration factor is regarded as the ratio between the maximal value of the stress in a body and the maximal value of the applied force for a given distribution of material properties. An optimal stress concentration factor is defined as the lowest stress concentration factor if we allow any stress field that is in equilibrium with the given load. The generalized stress concentration factor, a purely geometric property of a body, is the maximal optimal stress concentra...

  14. The Mohr stress circle: Determining stress and stress states

    Science.gov (United States)

    Seth Kruckenberg

    The goal of this exercise is to reinforce concepts discussed in lecture on the topic of stress and give students a hands on intuition of the relationships between the principal stresses, the normal and shear stresses, and the interaction of these quantaties on planes of varying orientation. The Mohr circle provides a graphical construction of stress equations and their systematic variation which is both practical and intuitive.

  15. Relationships Between the Phase Transformation Kinetics, Texture Evolution, and Microstructure Development in a 304L Stainless Steel Under Biaxial Loading Conditions: Synchrotron X-ray and Electron Backscatter Diffraction Studies

    Science.gov (United States)

    Cakmak, Ercan; Choo, Hahn; Kang, Jun-Yun; Ren, Yang

    2015-02-01

    The relationships between the martensitic phase transformation kinetics, texture evolution, and the microstructure development in the parent austenite phase were studied for a 304L stainless steel that exhibits the transformation-induced plasticity effect under biaxial loading conditions at ambient temperature. The applied loading paths included: pure torsion, simultaneous biaxial torsion/tension, simultaneous biaxial torsion/compression, and stepwise loading of tension followed by torsion (i.e., first loading by uniaxial tension and then by pure torsion in sequence). Synchrotron X-ray and electron backscatter diffraction techniques were used to measure the evolution of the phase fractions, textures, and microstructures as a function of the applied strains. The influence of loading character and path on the changes in martensitic phase transformation kinetics is discussed in the context of (1) texture-transformation relationship and the preferred transformation of grains belonging to certain texture components over the others, (2) effects of axial strains on shear band evolutions, and (3) volume changes associated with martensitic transformation.

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

    International Nuclear Information System (INIS)

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

  17. Prediction of stress relaxation under multiaxial stresses

    International Nuclear Information System (INIS)

    Computations have been made of the relaxation of residual stresses in a thick walled tube under conditions corresponding to commercial stress relief heat treatment of the nuclear reactor pressure vessel steel A533B. The distribution of residual stresses which were introduced was peaked around a given radius in the tube. The relax- ation of the equivalent stresses followed almost exactly a uniaxial behavior. The relaxation rate of the hydrostatic stress was of about the same order or slower than that of the equivalent stress. The time dependence of the hydrostatic stress was mainly controlled by the initial magnitude of hydrostatic stress whereas the degree of the constraint and thereby the boundary conditions at the tube walls had only a small influence. The relaxation rate decreased with increasing initial magnitude of the hydrostatic stress. The computed relaxation behaviour under multiaxial stress could be rationalized in terms of a developed model. This model was also suc- cessfully applied to Gott's measurements on stress relaxation during stress relief heat treatment of a welded joint between 130 mm thick plates of A533B where the stress state was highly triaxial. (Authors)

  18. Accurate Thermal Stresses for Beams: Normal Stress

    Science.gov (United States)

    Johnson, Theodore F.; Pilkey, Walter D.

    2003-01-01

    Formulations for a general theory of thermoelasticity to generate accurate thermal stresses for structural members of aeronautical vehicles were developed in 1954 by Boley. The formulation also provides three normal stresses and a shear stress along the entire length of the beam. The Poisson effect of the lateral and transverse normal stresses on a thermally loaded beam is taken into account in this theory by employing an Airy stress function. The Airy stress function enables the reduction of the three-dimensional thermal stress problem to a two-dimensional one. Numerical results from the general theory of thermoelasticity are compared to those obtained from strength of materials. It is concluded that the theory of thermoelasticity for prismatic beams proposed in this paper can be used instead of strength of materials when precise stress results are desired.

  19. Stress and Infertility

    Science.gov (United States)

    ... Website of the American Society for Reproductive Medicine Stress and infertility It is not clear how exactly ... during times of intense personal challenge. What is stress? Stress is often defined as an e vent ...

  20. Repetitive Stress Injuries

    Science.gov (United States)

    ... t had any problems since. What Are Repetitive Stress Injuries? Repetitive stress injuries (RSIs) are injuries that ... shoulders, knees, and heels. Continue What Causes Repetitive Stress Injuries? Most RSI conditions found in teens are ...

  1. Stress in America

    Science.gov (United States)

    ... Room // Stress in America Press Room EMAIL PRINT Stress in America Press Room Since 2007, the American ... 2013 2012 2011 2010 2009 2008 2007 2014 Stress in America: Paying With Our Health Press release ...

  2. Stress and Heart Health

    Science.gov (United States)

    Stress and Heart Health Updated:Jun 13,2014 When you’ve got an unexpected bill, a dead ... Health and Heart Health Last reviewed 6/2014 Stress Management • Home • How Does Stress Affect You? Introduction ...

  3. Analysis and optimization of oxide buffer layers related to YBCO films deposited by CSD and MOCVD on biaxially textured NiW substrates

    Energy Technology Data Exchange (ETDEWEB)

    Elmechaouri, E.; Moenter, B.; Hoffmann, M. [Bergische Univ. Wuppertal (Germany)

    2007-07-01

    The studies based on epitaxial buffer layers of CeO{sub 2} and Yttria-stabilised ZrO{sub 2} (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 CeO{sub 2}/YSZ/CeO{sub 2} 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 CeO{sub 2}/YSZ/CeO{sub 2} buffered substrates J{sub c} values higher than 2 MA/cm{sup 2}. The resulting superconducting properties were measured by inductive characterization and by Hall probe measurements of the magnetic field due to induced magnetization currents. (orig.)

  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. 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.

  6. Deposition of CeO2 and NiO buffer layers for YBCO coated conductors on biaxially textured Ni substrates by a MOCVD technique

    International Nuclear Information System (INIS)

    CeO2 and NiO buffers for YBCO coated conductors were deposited on biaxially textured Ni substrates by a metal-organic chemical vapor deposition method. The degree of texture and surface roughness of the oxide films were analyzed by X-ray pole figure, atomic force microscope (AFM) and scanning electron microscopy. The texture of deposited CeO2 films was a function of deposition temperature and oxygen partial pressure (PO2). The (2 0 0) texture of CeO2 was fully developed at T=500-520 deg. C and PO2=3.33 Torr. The growth rate of the CeO2 films was 200 nm/min at T=520 deg. C and PO2=2.30 Torr, which is much faster than those prepared by other physical deposition methods. The (2 0 0) texture of NiO was formed at T=450 deg. C and PO2=1.67 Torr. The full width half maximum of the both films was in the range of 8-10 deg. . The AFM surface roughness of the films was between 3.0-10 nm, depending on the deposition temperature

  7. Biaxially textured constantan alloy (Cu 55 wt%, Ni 44 wt%, Mn 1 wt%) substrates for YBa2Cu3O7-x coated conductors

    International Nuclear Information System (INIS)

    Commercially available constantan alloy rods (nominal composition Cu55-Ni44-Mn1 wt%) have been thermo-mechanically processed to develop biaxially textured substrates. It was found that the (001) recrystallization cube texture percentage could be increased from 72% to nearly 100% as the annealing temperature of the rolled substrates was increased from 750 to 1200 deg. C. A full width half maximum (FWHM) of 6.5 deg. in (111) phi scans and an FWHM of 4.9 deg. in (100) omega scans were observed in the substrates annealed at 1200 deg. C for 2 h. These substrates were found to have a Curie temperature of 35 K and so were paramagnetic at 77 K and ferromagnetic at 5 K with a saturation magnetization that is 2.5 times less than that of Ni-5 at.% W substrates. Yield strengths of highly textured constantan substrates were found to be 1.5 times that of textured pure Ni substrates at room temperature

  8. 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.

  9. 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.

  10. 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.

  11. Highly reinforced, low magnetic and biaxially textured Ni-7 at.%W/Ni-12 at.%W multi-layer substrates developed for coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Yue; Suo Hongli; Zhu Yonghua; Liu Min; He Dong; Ye Shuai; Ma Lin; Fan Ruifen; Zhou Meiling [Key Laboratory of Advanced Functional Materials, Ministry of Education, College of Materials Science and Engineering, Beijing University of Technology, 100 Pingleyuan, Chaoyang District, Beijing 100022 (China); Ji Yuan [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, 100 Pingleyuan, Chaoyang District, Beijing 100022 (China)], E-mail: honglisuo@bjut.edu.cn

    2008-07-15

    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 <001> {l_brace}100{r_brace} 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 {sigma}{sub 0.2} 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.

  12. High J{sub C} YBCO films on biaxially textured Ni with oxide buffer layers deposited using evaporation and sputtering techniques

    Energy Technology Data Exchange (ETDEWEB)

    Kreiskott, S.; Getta, M.; Moenter, B.; Piel, H.; Pupeter, N

    2003-01-01

    Epitaxial buffer layers of CeO{sub 2} and yttria-stabilised ZrO{sub 2} (YSZ) have been deposited on biaxially textured nickel substrates using evaporation and rf sputtering. The buffer layers were characterised by XRD, SEM and optical microscopy. YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films were deposited by high pressure dc sputtering on CeO{sub 2}/YSZ/CeO{sub 2} buffered substrates and the resulting superconducting properties were measured inductively. On exclusively evaporated buffers critical current densities of up to 0.6 MA/cm{sup 2} (77.3 K, H=0 T) were achieved. The buffer layers showed some cracks after YBCO deposition, which we considered to be responsible for the relatively low J{sub C}. In contrast buffer architectures with evaporated CeO{sub 2} followed by rf sputtering of YSZ and CeO{sub 2} remained completely free of cracks after YBCO deposition. Critical current densities between 1.5 and 2.6 MA/cm{sup 2} (77 K, H=0 T) in 400 nm thick YBCO films were obtained reproducibly. The critical temperatures T{sub C} ranged between 87 and 92 K and the typical width {delta}T{sub C} of the transition was 1.5 K.

  13. Fast neutron induced creep in pyrocarbon under constant stress

    International Nuclear Information System (INIS)

    Pyrocarbon is used as a coating material in the fuel of high-temperature nuclear reactors, and a thorough understanding of its irradiation behaviour includes a knowledge of its ability to creep under fast neutron irradiation. A experiment is described which demonstrates fast neutron-induced creep of a pyrolytic carbon under constant applied stress. This differs from previous work which has obtained creep ductility data from restrained shrinkage tests. The specimens were centre-loaded discs freely supported at the rim, thus subjected to a constant biaxial stress. On each specimen, elastic and plastic strains were produced and measured using the same geometry and loading arrangement to allow the creep strain to be expressed simply in terms of initial elastic strain units. Results were obtained on specimens of initial density 1.95 g/cm3 and 1.64g/cm3 up to a fast neutron dose of 4 x 1020 n/cm2 (DNE) at a temperature of 10000C. The low-density specimens showed both the greater shrinkage and the greater creep strain, and average creep rates were 0.5 and 1.0 elastic units per 1020 n/cm2 (DNE) for the high and low-density specimens respectively. These constant-stress creep results are shown to be consistent with other data on pyrocarbon. They differ from graphite creep data in that the two pyrocarbons give creep strains per unit initial elastic strain which depend on their initial densities. (Auth.)depend on their initial densities. (Auth.)

  14. 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…

  15. 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.…

  16. Analysis of linear elasticity and non-linearity due to plasticity and material damage in woven and biaxial braided composites

    Science.gov (United States)

    Goyal, Deepak

    Textile composites have a wide variety of applications in the aerospace, sports, automobile, marine and medical industries. Due to the availability of a variety of textile architectures and numerous parameters associated with each, optimal design through extensive experimental testing is not practical. Predictive tools are needed to perform virtual experiments of various options. The focus of this research is to develop a better understanding of linear elastic response, plasticity and material damage induced nonlinear behavior and mechanics of load flow in textile composites. Textile composites exhibit multiple scales of complexity. The various textile behaviors are analyzed using a two-scale finite element modeling. A framework to allow use of a wide variety of damage initiation and growth models is proposed. Plasticity induced non-linear behavior of 2x2 braided composites is investigated using a modeling approach based on Hill's yield function for orthotropic materials. The mechanics of load flow in textile composites is demonstrated using special non-standard postprocessing techniques that not only highlight the important details, but also transform the extensive amount of output data into comprehensible modes of behavior. The investigations show that the damage models differ from each other in terms of amount of degradation as well as the properties to be degraded under a particular failure mode. When compared with experimental data, predictions of some models match well for glass/epoxy composite whereas other's match well for carbon/epoxy composites. However, all the models predicted very similar response when damage factors were made similar, which shows that the magnitude of damage factors are very important. Full 3D as well as equivalent tape laminate predictions lie within the range of the experimental data for a wide variety of braided composites with different material systems, which validated the plasticity analysis. Conclusions about the effect of fiber type on the degree of plasticity induced non-linearity in a +/-25° braid depend on the measure of non-linearity. Investigations about the mechanics of load flow in textile composites bring new insights about the textile behavior. For example, the reasons for existence of transverse shear stress under uni-axial loading and occurrence of stress concentrations at certain locations were explained.

  17. Residual stress determination in PECVD TiN coatings by X-ray diffraction: a parametric study

    DEFF Research Database (Denmark)

    Thomsen, N.B.; Horsewell, Andy

    1998-01-01

    The main objective of this research is to study the residual macroscopic stress in titanium-nitride, TiN, coatings deposited onto a tool steer substrate. The measurements were performed with a theta-theta decoupled X-ray diffractometer. The coatings were manufactured using an industrial pulsed-DC plasma-enhanced chemical vapour deposition (PECVD) technique. The coatings were characterized in terms of microstructure, mechanical and tribological properties. A parametric study of the deposition parameters was performed. Process pressure, bias voltage, temperature and partial gas flows (argon, hydrogen, nitrogen and titanium tetra chloride) were varied in an effort to obtain optimal coating properties. Besides the bi-axial stress, the stress-free lattice constant, d(0), are presented as well as an indication of the changes in texture as a function of process parameter. Total macroscopic stress values were found to range from -1.5 to 1.5 GPa. The intrinsic stresses for the major part of the coatings were close to zero lending to low intrinsic strain energies favouring a preferred orientation of the coating corresponding to the plane with the lowest surface energy which is (200). Other properties are also discussed, e.g. microstructure, composition and hardness.

  18. An area-average approach to peening residual stress under multi-impacts using a three-dimensional symmetry-cell finite element model with plastic shots

    International Nuclear Information System (INIS)

    We estimate realistic peening residual stress based on area-averaged solution using a 3D multi-impact symmetry-cell finite element (FE) model. The analytical model includes elaborate factors reflecting actual peening phenomena and plastic shot effect. Area-averaged solution is much closer to X-ray diffraction (XRD) experimental solution than four-node-averaged solution in plastic shot FE model. The area-averaged solution, moreover, converges to the perfect equi-biaxial stress state. From this, based on the area-averaged solution, we obtained the FE Almen curve, and then derived related equations among FE arc height, FE coverage and shot velocity. The FE Almen curve corresponds well with experimentally obtained by Kim et al. [Kim T, Lee JH, Lee H. An Effective 2D FE model with plastic shot for evaluation of peening residual stress. J Mater Process Technol, submitted for publication; Kim T, Lee H, Lee JH. A 3D phenomenological FE model for unique solution of peening stress due to multi-impacts. Int J Numer Methods Eng, submitted for publication]. Using the FE Almen curve, we examine the FE area-averaged solution in major peening materials. The FE solutions of surface, maximum compressive residual stress and deformation depth quite reach experimental solutions. The FE Almen curve is thus confirmed to be useful for estimation of residual stress solution. Consequently, we validated that the concept of area-averaged solution is the systematical analytical method for evaluation of real peening residual stress.

  19. 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 exposed to CMAS glass at 1300°C for up to 48 hours. Stresses were measured as a function of depth in the multilayer coatings, and a compressive stress on the surface increased with exposure time from -50 MPa to a maximum of -160 MPa. Backscatter electron imaging and energy dispersive X-ray techniques demonstrated that infiltration depth of the glass increased with exposure time.

  20. STRESS MANAGEMENT PRACTICES & TIPS

    Directory of Open Access Journals (Sweden)

    UDAYSINH MANEPATIL

    2013-02-01

    Full Text Available 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.

  1. 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…

  2. 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.

  3. Managing Leadership Stress

    Science.gov (United States)

    Bal, Vidula; Campbell, Michael; McDowell-Larsen, Sharon

    2008-01-01

    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…

  4. 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.

  5. Caregiver Stress and Elder Abuse

    Science.gov (United States)

    ... stresses associated with providing care. What is caregiver stress and why is it harmful? Stress is often ... or even premature death. Do all caregivers experience stress? Some stress is normal. In the past, it ...

  6. Stress and stem cells

    OpenAIRE

    Tower, John

    2012-01-01

    The unique properties and functions of stem cells make them particularly susceptible to stresses and also lead to their regulation by stress. Stem cell division must respond to the demand to replenish cells during normal tissue turnover as well as in response to damage. Oxidative stress, mechanical stress, growth factors, and cytokines signal stem cell division and differentiation. Many of the conserved pathways regulating stem cell self-renewal and differentiation are also stress-response pa...

  7. Observation of asymmetrical two-cone Vavilov-Cherenkov radiation in biaxial crystal of triglycinesulphate emitted by 658 MeV protons passing along bi normal

    International Nuclear Information System (INIS)

    The paper deals with the directivity and polarization properties of the Vavilov-Cherenkov radiation (VChR) produced in passage of 658 MeV protons along an optical axis (bi normal) crystal of triglycinesulphate (TGS). The azimuthal distribution of the radiation turned out to be rather peculiar. First, it was asymmetrical about the plane running through the velocity vector of the beam particles perpendicularly to the plane of optical axes (POA). This VChR asymmetry was not observed in three earlier studied cases of 660 MeV protons passing through the main dielectric axes of a biaxial TGS crystal (i.e. when particles move along the small and the large bisectrix and perpendicularly to the plane of optical axes). Secondly, the azimuthal distribution of the VChR has a form of two symmetrical semi cones with different cone angles (their sections perpendicular to the proton beam axis resemble half-horseshoes inserted into each with their arcs outward). It also appeared that the outer VChR cone, F-, is practically polarized only in the POA, while the inner cone, F+, has more complicated polarization, i.e. in the angular region ? ? 900 perpendicularly to the POA. Formulae are obtained for radiation directivity at any angle ? for this asymmetrical two-cone radiation. Comparison of the VChR emission angles calculated by these formulae and measured in experiment shows good agreement (within the measurement errors for the azimuthal wave distribution of F+ (inner cone) and some systematic excess (? 0.50) for wave angles of F- (outer cone). 9 refs.; 5 figs.; 2 tabs

  8. 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.

  9. Effect of the alkyl chain length of the alcohols on the nematic uniaxial-to-biaxial phase transitions in the potassium laurate/alcohol/K2SO4/water lyotropic mixture

    OpenAIRE

    Akpinar, Erol; Reis, Dennys; Neto, Antonio Martins Figueiredo

    2012-01-01

    Lyotropic liquid crystalline quaternary mixtures of potassium laurate (KL), potassium sulphate (K2SO4)/alcohol (n-OH)/water, with the alcohols having different number of carbon atoms in the alkyl chain (n), from 1 octanol to 1-hexadecanol, were investigated by optical techniques (optical microscopy and laser conoscopy). The biaxial nematic phase domain is present in a window of values of n = nKL \\pm 2, where nKL = 11 is the number of carbon atoms in the alkyl chain of KL. Th...

  10. Influence of deposition conditions on mechanical properties of low-pressure chemical vapor deposited low-stress silicon nitride films

    International Nuclear Information System (INIS)

    The effect of deposition temperature, deposition pressure, or input gas ratio (SiH2Cl2:NH3) on film stress was determined for low-pressure chemical vapor deposited silicon nitride films. Wafer curvature measurements were performed for films deposited on single crystal silicon and amorphous silica wafer substrates to determine film stress ?dep, biaxial modulus Ef+, and coefficient of thermal expansion ?f. Apparent plane strain film modulus E-barf' and hardness H were measured using depth-sensing indentation. Ellipsometry was used to measure film thickness tf and refractive index n. Infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), forward recoil energy spectroscopy (FReS), and Rutherford backscattering spectroscopy (RBS) experiments were performed to determine film composition. Although film deposition stress varied from -135 MPa (compressive) to 235 MPa (tensile) Ef+, E-barf', H, and ?f remained nearly constant. Infrared spectroscopy resolved only Si-N species for all films, and results from FReS on three films confirmed that the hydrogen content was negligible. RBS and XPS indicated that Si/N increased with increased compressive ?dep. Ellipsometry and RBS indicated that all films were silicon-rich, to a greater extent with increased compressive ?dep. As RBS indicatesive ?dep. As RBS indicated that atomic density decreased with increased compressive deposition stress, it was concluded that the deposition conditions changed both thermal and intrinsic deposition stress for all films. In particular, intrinsic stress was tensile, and became increasingly tensile for increased Si/N and decreased atomic density. Assuming thermal stress was similar for all films examined here, the intrinsic stress must have varied from changes dependent on the deposition conditions

  11. Stress at Work Place

    OpenAIRE

    Shahrour, Mohammad A.

    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...

  12. Hvad er Stress? : Om historien bag 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 vores arbejdsliv, privatliv og samfund?

  13. Spatial variation in seismotectonics and stress conditions across the Kurile and Japan trenches inferred from the analysis of focal mechanism data in Hokkaido, northern Japan

    Science.gov (United States)

    Ghimire, Subesh; Kasahara, Minoru

    2009-03-01

    We analyzed seismotectonic characteristics of focal mechanism data across the Kurile and Japan trenches in the Hokkaido region, north Japan, to check for spatial variation in seismotectonics. For this purpose we selected highly constrained focal mechanism data from the Harvard CMT catalog and Japanese National Research Institute for Earth Science and Disaster Prevention (NIED) for the period 1976 to July 2007. Further, we selected data with high double couple components within a depth range of ±7.5 km from the inferred boundary of the subducting Pacific slab. We found a systematic variation in seismotectonic affinity of the data exhibiting eight distinct zones in the region. Among them, the outer rise region exhibits a normal fault regime with biaxial extension along and across the trenches. In the regions hosting the Pacific slab at shallow depths, most of the focal mechanism data lie in the thrust regime and the odd-event regime. This is due to a complicated stress condition with a major component of seismic deformation being accommodated by extensional and strike-slip movements in a thrust regime. Dominantly uniaxial compression acting downdip of the subducted Pacific slab is found in the regions hosting the rupture zones of large subduction earthquakes such that during an interseismic period tectonic stress is loaded by subduction. In the proximity of the Hidaka collision zone the stress conditions suggest that the impact of collision on ongoing seismotectonics is inevitable. In such regions we found thrust regimes with biaxial compression along the collision and subduction directions that favor bulging and/or contortion of the subducted slab.

  14. Takotsubo (Stress) Cardiomyopathy

    Science.gov (United States)

    ... Name Password Sign In Cardiology Patient Page Takotsubo (Stress) Cardiomyopathy Scott W. Sharkey , MD ; John R. Lesser , ... to normal. Previous Section Next Section Importance of Stress In 85% of cases, takotsubo is triggered by ...

  15. Exercise stress test

    Science.gov (United States)

    ... EKG - exercise treadmill; Stress ECG; Exercise electrocardiography; Stress test - exercise treadmill ... This test is done at a medical center or health care provider's office. The technician will place 10 flat, ...

  16. Stress Propagation in Sand

    CERN Document Server

    Cates, M E

    1998-01-01

    We describe a new continuum approach to the modelling of stress propagation in static granular media, focussing on the conical sandpile created from a point source. We argue that the stress continuity equations should be closed by means of scale-free, local constitutive relations between different components of the stress tensor, encoding the construction history of the pile: this history determines the organization of the grains, and thereby the local relationship between stresses. Our preferred model FPA (Fixed Principle Axes) assumes that the eigendirections (but not the eigenvalues) of the stress tensor are determined forever when a material element is first buried. Stresses propagate along a nested set of archlike structures within the medium; the results are in good quantitative agreement with published experimental data. The FPA model is one of a larger class, called OSL (Oriented Stress Linearity) models, in which the direction of the characteristics for stress propagation are fixed at burial. We spec...

  17. Stress and Wound Healing

    OpenAIRE

    Christian, Lisa M.; Graham, Jennifer E.; Padgett, David A.; Glaser, Ronald; Kiecolt-glaser, Janice K.

    2006-01-01

    Over the past decade it has become clear that stress can significantly slow wound healing: stressors ranging in magnitude and duration impair healing in humans and animals. For example, in humans, the chronic stress of caregiving as well as the relatively brief stress of academic examinations impedes healing. Similarly, restraint stress slows healing in mice. The interactive effects of glucocorticoids (e.g. cortisol and corticosterone) and proinflammatory cytokines [e.g. interleukin-1? (IL-1...

  18. 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 under the head, at the thread start or at the thread root. To minimize the stress concentration shape optimization is applied.

  19. Smoking and financial stress

    OpenAIRE

    Siahpush, M.; Borland, R.; Scollo, M.

    2003-01-01

    Aim: Stress relief is commonly provided as a reason for smoking. However, it is plausible that the cost of smoking may create financial stress, particularly among the poor. The aim of the study was to examine the relationship between smoking and financial stress.

  20. Stress in the Library.

    Science.gov (United States)

    Bunge, Charles

    1987-01-01

    Reports results of a survey of 800 library staff members on aspects of library work that they find stressful. The findings include sources of satisfaction and stress for all participants, and sources of stress specific to public services librarians, technical services librarians, and support staff members. (CLB)

  1. Managing Stress. Project Seed.

    Science.gov (United States)

    Muto, Donna; Wilk, Jan

    One of eight papers from Project Seed, this paper describes a stress management project undertaken with high school sophomores. Managing Stress is described as an interactive workshop that offers young people an opportunity to examine specific areas of stress in their lives and to learn effective ways to deal with them. The program described…

  2. Are You Stressed?

    Science.gov (United States)

    WSU's Student Success Center

    2010-06-14

    FYE Module Your Stress (Part 1) One of the best ways to deal with stress is to be aware of how much we're experiencing. Stress can be overt and in-your-face, like a violent crime, or stealthy and chronic, like your living environment. Sometimes we're unaware of how ...

  3. Electronic structure and biaxial strain in RbHgF3 perovskite and hybrid improper ferroelectricity in (Na,Rb)Hg2F6 and (K,Rb)Hg2F6 superlattices

    Science.gov (United States)

    Pilania, Ghanshyam; Lookman, Turab

    2014-09-01

    Here we study geometry, electronic structure, and effects of biaxial strain on RbHgF3 fluoro-perovskite from first-principles based density-functional theory computations. It has been shown that while an epitaxial strain of ˜±2% is sufficient to produce a significant ferroelectric polarization in the prototypical cubic Pm3¯m structure, the ground state orthorhombic Pnma structure remains effectively immune to the strain induced ferroelectricity even at biaxial strains as high as ±5%. We further show that RbHgF3 in the Pnma structure can accommodate compressive and tensile strains, respectively, by a-a-b0 tilting (out-of-phase tilts along a and b axes) and a0a0b+ rotations (in-phase rotations along c axis) of HgF2 octahedra. Similar to many perovskite oxides, HgF2 octahedral rotations in RbHgF3 are found to be accompanied by large Rb-site antipolar displacements along the [001] direction. We demonstrate that this coupling between the octahedral rotations and Rb-site antipolar modes can be harnessed in RbHgF3/NaHgF3 and RbHgF3/KHgF3 superlattices to produce significant net polarizations of 4.93 ?C/cm2 and 1.70 ?C/cm2, respectively.

  4. Crack initiation under thermal fatigue: An overview of CEA experience Part II (of II): Application of various criteria to biaxial thermal fatigue tests and a first proposal to improve the estimation of the thermal fatigue damage

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, A.; Gourdin, C.; Ancelet, O.; Demassieux, A.; Chapuliot, S. [CEA Saclay, Dept Modelisat Syst and Struct, Serv Etud Mecan and Therm, Lab Integrite Struct and Normalisat, 91 - Gif-sur-Yvette (France); Amiable, S.; Constantinescu, A. [Ecole Polytech, Mecan Solides Lab, CNRS, UMR 7649, F-91128 Palaiseau (France); Haddar, N. [Ecole Natl Ingenieur Sfax, Ecole Super Mines Paris, Sfax Tunisie (Tunisia); Mermaz, F.; Stelmaszyk, J. M. [Inst Radioprotect and Surete Nucl, F-92262 Fontenay Aux Roses (France); Vincent, L.; Maillot, V. [CEA Saclay, Serv Rech Met Appl, Lab Comportement and Dommage, 91 - Gif-sur-Yvette (France)

    2009-07-15

    A Part I accompanying paper clearly showed that for a given level of strain range (Delta epsilon), the number of cycles required to achieve crack initiation is significantly lower in biaxial thermal fatigue than in uniaxial isothermal fatigue. Such discrepancy does not come from a thermal effect, as it is emphasized by a comparison between the uniaxial data, coming either from thermomechanical fatigue tests, or from isothermal low cycle fatigue tests. A detrimental effect of multiaxial loading on fatigue life is noticed in many cases as reported in the literature. In this frame, the goal of this paper is to propose criteria in order to take into account the reduction of fatigue life resulting from the multi-axiality. Among all the examined multiaxial criteria, a criterion based on strain proposed by Zamrik, and a new criterion based on energy proposed by 'Ecole Polytechnique' give the best estimations. Furthermore, application of the Zamrik's criterion using the RCC-MR method is very promising for the design engineer. Indeed, these two criteria exhibit a notable potential, since they are well adapted to all the available thermal fatigue experimental data, despite significant differences between approaches and processes developed by both accessible facilities. However, such investigation must be continued with achievement of additional thermal fatigue tests (for higher number of cycles...), and isothermal biaxial fatigue tests. (authors)

  5. 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.

  6. [Skin and stress].

    Science.gov (United States)

    Consoli, S

    1996-12-01

    The concept of stress was developed based on data from experimental pathology and psychology studies. Selye defined stress and described the physiologic changes induced by stress, under the designation "general adaptation syndrome". The interactive aspect of stress has since then been emphasized. Stress results from a unique interaction between a thinking individual and a physical or social environment. The presence in humans of a mental apparatus capable of thinking, reminiscing, and fantasizing accounts for the specific features of stress as a clinical condition. It follows that psychosomatic dermatology cannot be satisfied with defining and documenting stress, with establishing a link between stress and a disorder of the skin (an organ that plays a unique role in communication), and with evaluating the biological mechanism underlying the skin lesions. Another essential goal is to understand why an individual patient, with his or her unique history, develops a skin disorder as a manifestation of an inability to cope with adversity. Two psychologic factors should be taken into account in dermatology, namely stress and the personality of the person subjected to the stress. What makes a life event stressful is often the personality of the subject experiencing the event. PMID:9157367

  7. Stress Reactivity in Insomnia.

    Science.gov (United States)

    Gehrman, Philip R; Hall, Martica; Barilla, Holly; Buysse, Daniel; Perlis, Michael; Gooneratne, Nalaka; Ross, Richard J

    2014-08-15

    This study examined whether individuals with primary insomnia (PI) are more reactive to stress than good sleepers (GS). PI and GS (n = 20 per group), matched on gender and age, completed three nights of polysomnography. On the stress night, participants received a mild electric shock and were told they could receive additional shocks during the night. Saliva samples were obtained for analysis of cortisol and alpha amylase along with self-report and visual analog scales (VAS). There was very little evidence of increased stress on the stress night, compared to the baseline night. There was also no evidence of greater stress reactivity in the PI group for any sleep or for salivary measures. In the GS group, stress reactivity measured by VAS scales was positively associated with an increase in sleep latency in the experimental night on exploratory analyses. Individuals with PI did not show greater stress reactivity compared to GS. PMID:25126695

  8. Stress distributions and energetics in the laterally ordered systems of buried pyramidal Ge/Si(001) islands: An atomistic simulation study

    Science.gov (United States)

    Makeev, Maxim A.; Yu, Wenbin; Madhukar, Anupam

    2003-11-01

    Stress distributions in laterally ordered arrays of coherent Ge islands of shallow pyramidal shape buried in a Si(001) matrix are studied via large-scale atomistic simulations, using Stillinger-Weber Ge/Si systems as a vehicle. The existence of tensile hydrostatic stress regions is observed on the spacer surface, above the buried islands. Our previously reported finding [M. A. Makeev and A. Madhukar, Phys. Rev. Lett. 86, 5542 (2001)] that the hydrostatic stress at the spacer layer surface above the island apex is nearly inversely proportional to the spacer layer thickness is validated by a comparison with experimental data. The lateral variations of the hydrostatic stress on the spacer layer surface show “bell-shape” profiles, with the effective size of the tensile regions above the island apex varying as a power law with the spacer layer thickness, with the power exponent being greater than 1. Studies of the energetics of twofold stacks of island systems show that the elastic interaction energy between the islands is minimized for the vertically aligned geometry. The spacer layer thickness dependence of the hydrostatic and biaxial stress field distributions in the interior of the Si(001) matrix are presented as these define the behavior of the electron and hole three-dimensional confinement potentials that determine the electronic properties of the pyramidal island quantum dots.

  9. Initiation behavior of stress corrosion cracking for type 316L stainless steel with controlled distribution of surface work hardened layer in high temperature water

    International Nuclear Information System (INIS)

    The stress corrosion cracking susceptibility is strongly affected by the properties of surface work hardened layer. Therefore, to fabricate the samples with reproducible surface is required for quantitative SCC initiation tests. The main focus of this study is to establish the preparation method of SCC initiation test sample using face milling. Furthermore, CBB test was conducted to evaluate the SCC susceptibility of these samples. Face milling was conducted on the commercial type 316L stainless steels with the cutting parameters of feed and spindle speed. Micro Vickers hardness tests and stress measurements using XRD were carried out to evaluate the distribution of properties of SCC test samples. The results obtained are as follows; (1) The cutting mark spacing and the depth of cut were controlled by feedrate. (2) The spacing and local hardness of high and low plastic strained region, average and standard deviation of hardness on surface were controlled by depth of polishing. (3) Residual stress introduced by face milling was bi-axial tensile stress. (4) The hardness distribution in high plastic strained region is equivalent to damaged core shroud H4 and surface grinding. (5) SCC was initiated on high plastic strained region. (6) CBB test results suggest that SCC susceptibility is related to hardness and stress distribution. (author)

  10. 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…

  11. Direct evidence for stress-induced texture evolution and grain growth of silver thin films upon thermal treatment and self-ion bombardment

    International Nuclear Information System (INIS)

    Common failure mechanisms in microelectronics, such as electromigration, creep and fatigue, can be positively influenced by microstructure optimization. In this paper a combination of post-deposition heat treatment and self-ion bombardment is proposed as a valid candidate to gain control over the microstructure of (1 1 1) fiber textured thin silver films. Irradiation can induce a strong in-plane texture and hence lead to biaxially textured films through a process of selective grain growth. Moreover, we report microstructural stability of the irradiated regions over a wide range of temperatures (up to 600 deg. C), in contrast to non-irradiated portions of the film, which underwent abnormal growth of the (1 0 0) out-of-plane oriented grains, and a consequent texture change, at temperatures as low as 195 deg. C. The thermal stress induced in the film upon heat treatment was quantified in situ and its role in texture change elucidated.

  12. Stress Corrosion of Glass

    International Nuclear Information System (INIS)

    This paper a review of environmentally induced stress corrosion (static fatigue) mechanisms of glass. The rates of extractions of glass constituents by alkali ion-exchange or silica dissolution in water and buffered solution were discussed as a basis of stress corrosion, and the strength in crease of abraded glasses after immersing in water was explained in terms of potential strengthening mechanisms. And a detailed chemical bond rupture model in silica glass for the interaction of the environment with mechanically strained bonds at a tip of crack was presented as a stress corrosion crack growth model. The stress corrosion behavior and static fatigue limit of glasses obtained by measuring crack velocity as a function of applied stress using the double-cantilever cleavage specimen were shown, and the effects of temperature, pH and vapor concentration on fracture behavior and the stages of stress corrosion was also discussed

  13. Stress Measurement System

    Science.gov (United States)

    1996-01-01

    Under the Aircraft Structural Integrity program, Langley Research Center and Stress Photonics developed an infrared-based stress measurement system for use in nondestructive evaluation of materials and structures. Stress Photonics commercialized the technology in the DeltaTherm 1000 system, used to compare designs and detect cracks in structures, especially for aging aircraft and bridges. The system combines digital signal processing technology with a special infrared camera to provide instantaneous thermal images and live differential images.

  14. Mental Health and Stress

    Science.gov (United States)

    Mrs. Falconer

    2007-03-18

    This project collects resources for studying mental health and stress issues with middle schoolers. Teens and stress Science NetLinks: The Laughing Brain 2: A Good Laugh Dealing with anger Stress-o-meter Look at each of the above sites. Choose one and read the content. Write a one-paragraph summary. Play interactive games and take quizzes. Keep a log of what you do. Tell which site you liked best and why. ...

  15. 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...

  16. Stresses in nanocrystalline materials

    OpenAIRE

    Sheng, Jianfeng

    2010-01-01

    Residual, mechanical stresses in thin films are of great importance for the reliability and performance of film systems in technological applications. The residual stresses can be due to the deposition process, the mismatch of the coefficients of thermal expansion of the thin film(s) and the substrate upon cooling or heating (thermal stresses), interdiffusion (differences in the molar volumes and differences in the atomic fluxes of the diffusing species), (continued) grain growth, excess vaca...

  17. Learning During Stressful Times

    OpenAIRE

    Shors, Tracey J.

    2004-01-01

    Stressful life events can have profound effects on our cognitive and motor abilities, from those that could be construed as adaptive to those not so. In this review, I discuss the general notion that acute stressful experience necessarily impairs our abilities to learn and remember. The effects of stress on operant conditioning, that is, learned helplessness, as well as those on classical conditioning procedures are discussed in the context of performance and adaptation. Studies indicating se...

  18. Stressed and Strained

    Science.gov (United States)

    Integrated Teaching and Learning Program,

    Students are introduced to the concepts of stress and strain with examples that illustrate the characteristics and importance of these forces in our everyday lives. They explore the factors that affect stress, why engineers need to know about it, and the ways engineers describe the strength of materials. In an associated literacy activity, while learning about the stages of group formation, group dynamics and team member roles, students discover how collective action can alleviate personal feelings of stress and tension.

  19. Salivary mental stress proteins.

    Science.gov (United States)

    Obayashi, Konen

    2013-10-21

    Of the major diagnostic specimen types, saliva is one of the most easily collected. Many studies have focused on the evaluation of salivary proteins secreted by healthy people and patients with various diseases during responses to acute mental stress. In particular, such studies have focused on cortisol, ?-amylase, chromogranin A (CgA), and immunoglobulin A (IgA) as salivary stress markers. Each of these salivary stress markers has its own strengths and weaknesses as well as data gaps related to many factors including collection technique. In this review, we summarize the critical knowledge of the positive and negative attributes and data gaps pertaining to each salivary stress marker. PMID:23939251

  20. The teacher under stress

    Directory of Open Access Journals (Sweden)

    Krnjaji? 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.

  1. 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, which results in a more evenly distribution of load along the engaged thread, has a limited influence on the maximum stress due to the stress concentration at the first thread root. To further reduce the maximum stress, the transition from bolt shank to the thread must be optimized. Stress reduction of up to 34% is found, still with the standard International Organization for Standardization thread. The design changes suggested in this article also have the positive advantage of reducing the joint stiffness factor. The reduction in the bolt shank directly reduces the bolt stiffness but the design 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.

  2. Stresses in Dolosse

    DEFF Research Database (Denmark)

    Burcharth, Hans F.; Liu, Zhou

    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 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.

  3. Design for thermal stresses

    CERN Document Server

    Barron, Randall F

    2011-01-01

    The tools engineers need for effective thermal stress design Thermal stress concerns arise in many engineering situations, from aerospace structures to nuclear fuel rods to concrete highway slabs on a hot summer day. Having the tools to understand and alleviate these potential stresses is key for engineers in effectively executing a wide range of modern design tasks. Design for Thermal Stresses provides an accessible and balanced resource geared towards real-world applications. Presenting both the analysis and synthesis needed for accurate design, the book emphasizes key principles,

  4. 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 physical and emotional employers ( to do perfect job all the well being. time B. Avoiding pitfalls: by identifying 3. Long hours of stressful work knee jerks habits and negative attitudes

  5. Stress inversion assumptions review

    Science.gov (United States)

    Lejri, Mostfa; Maerten, Frantz; Maerten, Laurent; Joonnenkindt, Jean Pierre; Soliva, Roger

    2014-05-01

    Wallace (1951) and Bott (1959) were the first to introduce the idea that the slip on each fault surface has the same direction and sense as the maximum shear stress resolved on that surface. This hypothesis are based on the assumptions that (i) faults are planar, (ii) blocks are rigid, (iii) neither stress perturbations nor block rotations along fault surfaces occur and (iv), the applied stress state is uniform. However, this simplified hypothesis is questionable since complex fault geometries, heterogeneous fault slip directions, evidences of stress perturbations in microstructures and block rotations along fault surfaces were reported in the literature. Earlier numerical geomechanical models confirmed that the striation lines (slip vectors) are not necessarily parallel to the maximum shear stress vector but is consistent with local stress perturbations. This leads us to ask as to what extent the Wallace and Bott simplifications are reliable as a basis hypothesis for stress inversion. In this presentation, a geomechanical multi-parametric study using 3D boundary element method (BEM), covering (i) fault geometries such as intersected faults or corrugated fault surfaces, (ii) the full range of Andersonian state of stress, (iii) fault friction, (iv) half space effect and (v), rock properties, is performed in order to understand the effect of each parameter on the angular misfit between geomechanical slip vectors and the resolved shear stresses. It is shown that significant angular misfits can be found under specific configurations and therefore we conclude that stress inversions based on the Wallace-Bott hypothesis might sometime give results that should be interpreted with care. Major observations are that (i) applying optimum tectonic stress conditions on complex fault geometries can increase the angular misfit, (ii) elastic material properties, combined to half-space effect, can enhance this effect, and (iii) an increase of the sliding friction leads to a reduction of this misfit.

  6. 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 (?1, ?2) 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)

  7. Stress-ING Out: Phosphoinositides Mediate the Cellular Stress Response

    Science.gov (United States)

    Matthew W. Bunce (University of Wisconsin; Department of Pharmacology REV)

    2006-11-07

    Phosphoinositides regulate numerous cellular processes required for growth, proliferation, and motility. Whereas phosphoinositide signal transduction pathways within the cytosol have been well characterized, nuclear signaling pathways remain poorly understood. Accumulating experimental data have now started to uncover critical functions for nuclear phosphoinositides. In particular, phosphoinositides modulate the activity of the tumor suppressor protein ING2 in response to extracellular stress. These findings highlight a previously uncharacterized function for phosphoinositides and implicate their metabolism in signaling pathways critical for cell survival.

  8. Stress and its effect on optical properties of GaN epilayers grown on Si(111), 6H-SiC(0001), and c-plane sapphire

    Science.gov (United States)

    Zhao, D. G.; Xu, S. J.; Xie, M. H.; Tong, S. Y.; Yang, Hui

    2003-07-01

    The stress states in unintentionally doped GaN epilayers grown on Si(111), 6H-SiC(0001), and c-plane sapphire, and their effects on optical properties of GaN films were investigated by means of room-temperature confocal micro-Raman scattering and photoluminescence techniques. Relatively large tensile stress exists in GaN epilayers grown on Si and 6H-SiC while a small compressive stress appears in the film grown on sapphire. The latter indicates effective strain relaxation in the GaN buffer layer inserted in the GaN/sapphire sample, while the 50-nm-thick AlN buffer adopted in the GaN/Si sample remains highly strained. The analysis shows that the thermal mismatch between the epilayers and the substrates plays a major role in determining the residual strain in the films. Finally, a linear coefficient of 21.1±3.2 meV/GPa characterizing the relationship between the luminescent bandgap and the biaxial stress of the GaN films is obtained.

  9. CD-ROM Stress.

    Science.gov (United States)

    Bunge, Charles A.

    1991-01-01

    Discussion of stress in library reference departments focuses on stress caused by CD-ROM reference tools. Topics discussed include work overload; nonreference duties; patron attitudes and behavior; staff attitudes; the need for proper staff training; and the need for library administrators to be sensitive to reference staff needs. (LRW)

  10. Feel the Stress

    Science.gov (United States)

    GK-12 Program, School of Engineering and Applied Science,

    Working individually or in groups, students explore the concept of stress (compression) through physical experience and math. They discover why it hurts more to poke themselves with mechanical pencil lead than with an eraser. Then they prove why this is so by using the basic equation for stress and applying the concepts to real engineering problems.

  11. 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.

  12. Leveraging Stress Level

    OpenAIRE

    Pathak, Mitali

    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.

  13. Risk/Stress Analysis.

    Science.gov (United States)

    Schwerdtfeger, Don; Howell, Richard E.

    1986-01-01

    Identifies stress as a definite health hazard and risk factor involved in a variety of health situations. Proposes that stress identification efforts be considered in environmental analysis so that a more complete approach to risk assessment and management and health hazard prevention can occur. (ML)

  14. Actively stressed marginal networks.

    Science.gov (United States)

    Sheinman, M; Broedersz, C P; MacKintosh, F C

    2012-12-01

    We study the effects of motor-generated stresses in disordered three-dimensional fiber networks using a combination of a mean-field theory, scaling analysis, and a computational model. We find that motor activity controls the elasticity in an anomalous fashion close to the point of marginal stability by coupling to critical network fluctuations. We also show that motor stresses can stabilize initially floppy networks, extending the range of critical behavior to a broad regime of network connectivities below the marginal point. Away from this regime, or at high stress, motors give rise to a linear increase in stiffness with stress. Finally, we demonstrate that our results are captured by a simple, constitutive scaling relation highlighting the important role of nonaffine strain fluctuations as a susceptibility to motor stress. PMID:23368268

  15. Actively stressed marginal networks

    CERN Document Server

    Sheinman, M; MacKintosh, F C

    2012-01-01

    We study the effects of motor-generated stresses in disordered three dimensional fiber networks using a combination of a mean-field, effective medium theory, scaling analysis and a computational model. We find that motor activity controls the elasticity in an anomalous fashion close to the point of marginal stability by coupling to critical network fluctuations. We also show that motor stresses can stabilize initially floppy networks, extending the range of critical behavior to a broad regime of network connectivities below the marginal point. Away from this regime, or at high stress, motors give rise to a linear increase in stiffness with stress. Finally, we demonstrate that our results are captured by a simple, constitutive scaling relation highlighting the important role of non-affine strain fluctuations as a susceptibility to motor stress.

  16. Stress, Arousal, and Sleep.

    Science.gov (United States)

    Sanford, Larry D; Suchecki, Deborah; Meerlo, Peter

    2014-05-23

    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 at least a brief period of arousal and wakefulness, the subsequent amount and architecture of recovery sleep can vary dramatically across conditions even though classical markers of acute stress such as corticosterone are virtually the same. Sleep after stress appears to be highly influenced by situational variables including whether the stressor was controllable and/or predictable, whether the individual had the possibility to learn and adapt, and by the relative resilience and vulnerability of the individual experiencing stress. There are multiple brain regions and neurochemical systems linking stress and sleep, and the specific balance and interactions between these systems may ultimately determine the alterations in sleep-wake architecture. Factors that appear to play an important role in stress-induced wakefulness and sleep changes include various monominergic neurotransmitters, hypocretins, corticotropin releasing factor, and prolactin. In addition to the brain regions directly involved in stress responses such as the hypothalamus, the locus coeruleus, and the amygdala, differential effects of stressor controllability on behavior and sleep may be mediated by the medial prefrontal cortex. These various brain regions interact and influence each other and in turn affect the activity of sleep-wake controlling centers in the brain. Also, these regions likely play significant roles in memory processes and participate in the way stressful memories may affect arousal and sleep. Finally, stress-induced changes in sleep-architecture may affect sleep-related neuronal plasticity processes and thereby contribute to cognitive dysfunction and psychiatric disorders. PMID:24852799

  17. The Trier Social Stress Test Protocol for Inducing Psychological Stress

    OpenAIRE

    Birkett, Melissa A.

    2011-01-01

    This article demonstrates a psychological stress protocol for use in a laboratory setting. Protocols that allow researchers to study the biological pathways of the stress response in health and disease are fundamental to the progress of research in stress and anxiety.1 Although numerous protocols exist for inducing stress response in the laboratory, many neglect to provide a naturalistic context or to incorporate aspects of social and psychological stress. Of psychological stress protocol...

  18. Stress Intensity Factors - T-Stresses - Weight Functions

    OpenAIRE

    Fett, Theo

    2008-01-01

    Failure of cracked components is governed by the stresses in the vicinity of the crack tip. The singular stress contribution is characterised by the stress intensity factor K, the first regular stress term is represented by the so-called T-stress. Sufficient information about the stress state is available, if these two parameters are known Results for K and T are compiled in form of figures, tables, and approximate relations.

  19. STRESS ETHYLENE PRODUCTION - A MEASURE OF PLANT RESPONSE TO STRESS

    Science.gov (United States)

    Contents: Introduction to the symposium; Environmental data acquisition; Plant organ chambers in plant physiology field research; Interpreting the metabolic responses of plants to water stress; Stress ethylene production....

  20. 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…