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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. 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)

  4. 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.

  5. Acoustic emission under biaxial stresses in unflawed 21-6-9 and 304 stainless steel

    International Nuclear Information System (INIS)

    Acoustic emission (AE) testing has been carried out with uniaxial and biaxial (2:1 stress ratio) stressing of smooth samples of 21-6-9 and 304 stainless steel (SS). Uniaxial testing was done with simple tensile and compression samples as well as with the special biaxial specimens. Biaxial tensile stressing was accomplished with a specially designed specimen, which had been used previously to characterize AE in 7075 aluminum under biaxial stressing. Results were obtained for air-melt and for vacuum-melt samples of 21-6-9 SS. The air-melt samples contain considerably more inclusion particles than the vacuum-melt samples. For the 304 SS, as received material was examined. To allow AE correlations with microstructure, extensive characterization of the 21-6-9 microstructure was carried out. Significant differences in AE occur in biaxially stressed specimens as compared to uniaxially stressed samples. 15 figures, 3 tables

  6. 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.

  7. 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.

  8. A Novel Biaxial Specimen for Inducing Residual Stresses in Thermoset Polymers and Fibre Composite Material

    DEFF Research Database (Denmark)

    Jakobsen, Johnny; Andreasen, Jens Henrik

    2014-01-01

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

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

    DEFF Research Database (Denmark)

    Jakobsen, Johnny; Andreasen, Jens Henrik

    2015-01-01

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

  10. Influences of equal biaxial tensile loads on the stress fields near the mixed mode crack

    International Nuclear Information System (INIS)

    A hybrid method for photoelasticity is introduced and applied to the plane problems of isotropic polycarbonate plates with a central crack under uniaxial and equal biaxial tensile loads. Also, the influences of equal biaxial tensile loads on the isochromatic fringes, stress fields and stress intensity factors near the mixed mode crack-tip have been investigated. The results show that, when an equal lateral tensile load is added to the specimen under uniaxial tensile load, the asymmetric isochromatic fringes about the line of crack gradually become symmetric, and the slope of the isochromatic fringe loop near the crack-tip is inclined towards the crack surface according to the increasing of the inclined angle of crack. Furthermore, the shapes of distribution of all stress components are changed from asymmetric to symmetric. In the equal biaxial tensile load condition against the uniaxial tensile load condition, the values of stress intensity factors are changed little, and only the region of compressive stress of ?x /?0 is changed when ? = 0 .deg., but the values of KI/K0 are increased and those of KII/K0 become almost zero, namely, we have the mode I condition when ? =15 .deg.?45 .deg.

  11. Influences of equal biaxial tensile loads on the stress fields near the mixed mode crack

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Dong Chul; Lee, Joon Hyun [Pusan National University, Busan (Korea, Republic of); Nam, Jeong Hwan; Hawong, Jai Sug [Yeungnam University, Gyoungsan (Korea, Republic of)

    2009-08-15

    A hybrid method for photoelasticity is introduced and applied to the plane problems of isotropic polycarbonate plates with a central crack under uniaxial and equal biaxial tensile loads. Also, the influences of equal biaxial tensile loads on the isochromatic fringes, stress fields and stress intensity factors near the mixed mode crack-tip have been investigated. The results show that, when an equal lateral tensile load is added to the specimen under uniaxial tensile load, the asymmetric isochromatic fringes about the line of crack gradually become symmetric, and the slope of the isochromatic fringe loop near the crack-tip is inclined towards the crack surface according to the increasing of the inclined angle of crack. Furthermore, the shapes of distribution of all stress components are changed from asymmetric to symmetric. In the equal biaxial tensile load condition against the uniaxial tensile load condition, the values of stress intensity factors are changed little, and only the region of compressive stress of {sigma}{sub x} /{sigma}{sub 0} is changed when {beta} = 0 .deg., but the values of K{sub I}/K{sub 0} are increased and those of K{sub I}I/K{sub 0} become almost zero, namely, we have the mode I condition when {beta} =15 .deg.{approx}45 .deg.

  12. Evaluation of stress intensity factor of multiple inclined cracks under biaxial loading

    Directory of Open Access Journals (Sweden)

    A.K. Chaudhary

    2012-10-01

    Full Text Available A finite rectangular plate of unit thickness with two inclined cracks (parallel and non parallel under biaxial mixed mode condition are modelled using finite element method. The finite element method is used for determination of stress intensity factors by ANYSIS software. Effects of crack inclination angle on stress intensity factors for two parallel and non parallel cracks are investigated. The significant effects of different crack inclination parameters on stress intensity factors are seen for lower and upper crack in two inclined crack. The present method is validated by comparing the results from available experimental data obtained by photo elastic method in same condition.

  13. Anisotropic biaxial stresses in diamond films by polarized Raman spectroscopy of cubic polycrystals

    Science.gov (United States)

    Gries, T.; Vandenbulcke, L.; Simon, P.; Canizares, A.

    2008-07-01

    The anisotropic stresses in diamond films induced by permanent deformations of titanium tensile substrates are studied by polarized Raman spectroscopy. The influence of the in-plane orientation of each grain relative to the stress directions is shown experimentally and theoretically. Considering the dynamical equations under small strains, the solutions of the secular equation permit the determination of the triply degenerate phonon frequency of polycrystalline diamond, which splits into three singlets for each crystallite. The calculation is carried out here for six growth directions, along [001], [110], [111], [112], [113], and [331], and for all in-plane orientations normal to these textures. In the case of anisotropic stresses, it is shown how the relative values of the two stresses induce different shapes in the Raman spectra. For an isotropic polycrystalline diamond film, this Raman spectroscopy of strained cubic polycrystals approximates the complete solution for all crystallite orientations relative to the anisotropic biaxial stresses. It allows calculating theoretical Raman spectra that fairly well compare to the experimental ones. The determination of the anisotropic stresses is obtained with a better accuracy when the influence of all orientations is taken into account than with the previous average procedures used for isotropic cubic polycrystalline materials. Partially or completely textured films along one of the growth directions can also be studied. If the stresses along the two directions are identical, the particular case of isotropic biaxial stresses is also studied with a better accuracy.

  14. Stress-strain state and stress intensity factor in the vicinity of crack-like defects under biaxial tension of a plate

    Science.gov (United States)

    Ostsemin, A. A.; Utkin, P. B.

    2014-11-01

    The problem of determining a stress-strain state described by singular and regular terms and a stress intensity factor in the vicinity of the tip of a crack-like defect in a plate under biaxial loading is considered. The Kolosov-Muskhelishvili method is used to obtain expressions for the stress tensor near the vertex of an ellipse, which yield formulas for stresses in the case of blunt cracks. The maximum shear stress, principal stresses, and stress intensity are determined. Formulas for the stress intensity factor under biaxial loading of a plate with a crack-like defect are obtained and can be used in the holographic interferometry method.

  15. 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)

  16. 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)

  17. 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)

  18. Determination of the biaxial stress in strained silicon nano-stripes through polarized oblique incidence Raman spectroscopy

    Science.gov (United States)

    Ndong, G.; Picardi, G.; Licitra, C.; Rouchon, D.; Eymery, J.; Ossikovski, R.

    2013-10-01

    We report on the experimental determination of the biaxial stress characteristic of the strain state present in strained silicon nano-stripes on insulator structures. Conventional confocal backscattering Raman spectroscopy being insensitive to the tensorial nature of strain, a methodology based on the use of polarized oblique incidence backscattering Raman spectroscopy is employed. The stress component values thus obtained are compared with those provided by grazing incidence x-ray diffraction as a reference technique. By combining the oblique backscattering configuration with polarization control of the incident and scattered beams, an efficient method for the accurate measurement of biaxial stress in patterned silicon structures results.

  19. 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.

  20. 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

  1. Model for analysis of biaxial and triaxial stresses by x-ray diffraction assuming orthotropic materials

    International Nuclear Information System (INIS)

    In this work we aim to develop expressions for the calculation of biaxial and triaxial stresses in polycrystalline anisotropic materials, and to determine their elastic constants using the theory of elasticity for continuum isochoric deformations; thus, we also derive a model to determine residual stress. The constitutive relation between strain and stress in these models must be assumed to be orthotropic, obeying the generalized Hooke's law. One technique that can be applied with our models is that of X-ray diffraction, because the experimental conditions are similar to the assumptions in the models, that is, it measures small deformations compared with the sample sizes and the magnitude of the tensions involved, and is insufficient to change the volume (isochoric deformation). Therefore, from the equations obtained, it is possible to use the sin2 ? technique for materials with texture or anisotropy by first characterizing the texture through the pole figures to determine possible angles ? that can be used in the equation, and then determining the deformation for each diffraction peak with the angles ? obtained from the pole figures. (author)

  2. Model for Analysis of Biaxial and Triaxial Stresses by X-ray Diffraction Assuming Orthotropic Materials

    Science.gov (United States)

    Santos, Edson M.; Orlando, Marcos T. D.; Miltão, Milton S. R.; Martinez, Luis G.; Alves, Alvaro S.; Passos, Carlos A.

    2010-05-01

    In this work we aim to develop expressions for the calculation of biaxial and triaxial stresses in polycrystalline anisotropic materials, and to determine their elastic constants using the theory of elasticity for continuum isochoric deformations; thus, we also derive a model to determine residual stress. The constitutive relation between strain and stress in these models must be assumed to be orthotropic, obeying the generalized Hooke's law. One technique that can be applied with our models is that of X-ray diffraction, because the experimental conditions are similar to the assumptions in the models, that is, it measures small deformations compared with the sample sizes and the magnitude of the tensions involved, and is insufficient to change the volume (isochoric deformation). Therefore, from the equations obtained, it is possible to use the sin 2? technique for materials with texture or anisotropy by first characterizing the texture through the pole figures to determine possible angles ? that can be used in the equation, and then determining the deformation for each diffraction peak with the angles ? obtained from the pole figures.

  3. Optimization of the magnetic properties of Co/Pd multilayers by applying a large persistent in-plane biaxial stress

    Energy Technology Data Exchange (ETDEWEB)

    Mohanan, Senthilnathan; Herr, Ulrich [Insitut fuer Mikro- und Nanomaterialien, Universitaet Ulm, 89081 Ulm (Germany)

    2008-07-01

    Co/Pd multilayers exhibiting perpendicular magnetic anisotropy (PMA) are promising candidates for perpendicular recording media. In these multilayers, stress induced magnetic anisotropy contributes significantly to the PMA due to the high negative magnetostriction constant. We present a study about the optimization of the magnetic properties of Co/Pd multilayers by changing the magnetoelastic contribution to the anisotropy energy. An in-plane biaxial tensile stress was applied to the Co/Pd multilayers by loading the Ta substrate with hydrogen. In-situ x-ray analysis during hydrogen loading and unloading showed that the hydrogen can absorb and desorb from the Co/Pd multilayer under the conditions used, but that it remains in the Ta substrate after exposing the sample to air again. This leads to a persistent in-plane biaxial stress of up to 2.8 GPa in the Co/Pd multilayers. We observed an increase of H{sub c} and the remanent magnetization with increasing biaxial stress. Analysis of the effective perpendicular anisotropy K{sub eff} in terms of a simple model yields the corresponding magnetostriction constants.

  4. Effective X-ray elastic constant measurement for in situ stress measurement of biaxially strained AA5754-O

    International Nuclear Information System (INIS)

    Accurate measurement of stresses by X-ray diffraction requires accurate X-ray elastic constants. Calibration experiments are one method to determine these for a specific material in a specific condition. In this paper, uniaxial tension experiments are used to investigate the variation of these constants after uniaxial and equal-biaxial plastic deformation for an aluminum alloy (AA5754-O) of interest to the automotive industry. These data are critical for accurate measurement of the biaxial mechanical properties of the material using a recent experimental method combining specialized sheet metal forming equipment with portable X-ray diffraction equipment. The measured effective X-ray elastic constants show some minor variation with increased plastic deformation, and this behavior was found to be consistent for both uniaxially and equal-biaxially strained samples. The use of two average values for effective X-ray elastic constants, one in the rolling direction and one transverse to the rolling direction of the sheet material, is shown to be of sufficient accuracy for the combined tests of interest. Comparison of uniaxial data measured using X-ray diffraction and standard methods show good agreement, and biaxial stress–strain results show good repeatability. Additionally, the calibration data show some non-linear behavior, which is analyzed in regards to crystallographic texture and intergranular stress effects. The non-linear behavior is found to be the result of intehavior is found to be the result of intergranular stresses based on comparison with additional measurements using other X-ray diffraction equipment and neutron diffraction.

  5. Determination of out-of-plane biaxial stress effects on fracture toughness for shallow surface cracks in reactor pressure vessel steels

    International Nuclear Information System (INIS)

    Pressurized-thermal-shock loading in a reactor pressure vessel (RPV) produces significant positive out-of-plane stresses along the crack front for both circumferential and axial cracks. Experimental evidence, while very limited, seems to indicate that a reduction in toughness is associated with out-of-plane biaxial loading when compared with toughness values obtained under uniaxial conditions. The motivation and objectives of a testing program to determine the effects of out-of-plane biaxial loading on fracture toughness of RPV steels are presented. A cruciform bend specimen that meets specified criteria for the testing program is analyzed using three-dimensional, elastic-plastic, finite-element techniques. These analysis results provide the basis for proposed test conditions that are judged likely to produce a biaxial loading effect in the cruciform bend specimen

  6. 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.

  7. Creep behavior of Portland cement, mortar, and concrete under biaxial stress

    Energy Technology Data Exchange (ETDEWEB)

    Kesler, C.E.

    1977-03-01

    Equipment developed at the Oak Ridge National Laboratory was used to make uniaxial and biaxial creep tests on mortar, normal weight concrete and lightweight concrete using both sealed and unsealed specimens. Some of the results are questionable because of the poor performance of the strain gages. Nevertheless, useful information was obtained on shrinkage, creep and Poisson's ratio. Generally speaking, the results were consistent with the work of other investigators. Both the shrinkage and creep were highest for the mortar and lowest for the normal weight concrete and intermediate for the lightweight concrete. The shrinkage and creep were highest for the unsealed specimens. A Poisson's ratio effect in creep was noted but the magnitudes were slightly less than those expected for elastic loadings.

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

    International Nuclear Information System (INIS)

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

  9. 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.

  10. 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.

  11. Investigation of in-plane biaxial low cycle fatigued austenitic stainless steel AISI 321. II. Neutron diffraction stress analysis at the IBR-2 pulsed nuclear reactor

    International Nuclear Information System (INIS)

    The in-plane biaxial low cycle fatigued sample of the cruciform geometry from austenitic stainless steel AISI 321 was investigated on the time-of-flight neutron Fourier stress-diffractometer. The lattice parameters in the austenite matrix and the martensite inclusions created during the fatigue cycling as well as the martensite volume fraction were measured along two mutually perpendicular planar axes of the sample of the cruciform geometry by using the strain neutron scanner. The phase total residual strain components were calculated using the stress equilibrium relations. The separation of the residual stresses into macro- and microstresses was performed using the mixture rule. The measurements of the applied load-phase elastic strain responses were carried out on a uniaxial load machine. The strong difference between the phase elastic moduli was found out

  12. Biaxial model for bounding creep ratcheting in shells

    International Nuclear Information System (INIS)

    The concept of elastic core stress is used to derive bounds for the maximum inelastic strains in shells of revolution subjected to pressure and cyclic thermal loads in the creep regime. Solutions are obtained for primary membrane stresses of arbitrary biaxiality and thermal bending of arbitrary biaxiality. The stress regimes where previously derived uniaxial solutions can be conservatively used are defined. The new biaxial solutions provide more efficient bounds than the uniaxial solutions for the maximum strains in pressurized spheres and cylinders. (orig.)

  13. 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.

  14. 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)

  15. A Langevin-elasticity-theory-based constitutive equation for rubberlike networks and its comparison with biaxial stress-strain data. Part I.

    Czech Academy of Sciences Publication Activity Database

    Meissner, Bohumil; Mat?jka, Libor

    2003-01-01

    Ro?. 44, ?. 16 (2003), s. 4599-4610. ISSN 0032-3861 R&D Projects: GA ?R GA104/00/1311; GA AV ?R IAA4050008 Institutional research plan: CEZ:AV0Z4050913 Keywords : theory of rubber elasticity * biaxial deformations * experimental testing Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.340, year: 2003

  16. A Langevin-elasticity-theory-based constitutive equation for rubberlike networks and its comparison with biaxial stress-strain data. Part II.

    Czech Academy of Sciences Publication Activity Database

    Meissner, Bohumil; Mat?jka, Libor

    2004-01-01

    Ro?. 45, ?. 21 (2004), s. 7247-7260. ISSN 0032-3861 R&D Projects: GA ?R GA104/00/1311; GA AV ?R IAA4050008 Institutional research plan: CEZ:AV0Z4050913 Keywords : theory of rubber elasticity * biaxial deformations * experimental testing Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.433, year: 2004

  17. Diffraction measurements of elastic strains in stainless steel subjected to in situ biaxial loading

    International Nuclear Information System (INIS)

    The lattice strains in AL6XN stainless steel specimens subjected to in situ biaxial stress states have been measured by neutron diffraction. The biaxial stress states were generated in tubular specimens using a specially designed loading apparatus that is capable of applying axial loads to specimens under internal pressure. Lattice strains in the axial and hoop directions were measured for different levels of stress biaxiality in numerous loaded and partially unloaded states. The results revealed the role of the biaxial stress state in the differences in average lattice strains between various crystallographic fibers. These trends are examined in light of the orientational dependencies of the lattice strains on the stress biaxiality under an assumption of uniform stress. Possible additional factors contributing to the observed trends are discussed

  18. Biaxial strength of HY 80 steel

    Energy Technology Data Exchange (ETDEWEB)

    Chan, K.S.; Lindholm, U.S.; Wise, J.

    1985-04-01

    The biaxial deformation behavior of HY 80 steel has been examined by testing thin wall tubes under combined axial tension and internal pressure. The effective stressstrain curves and the hardening response have been found to vary with the stress state. The plastic strain ratio at a given stress ratio deviates from the von Mises value except at the stress states near uniaxial tension, plane strain and equi-biaxial tension. Using Drucker theory, these deviations are eliminated and the resulting yield locus is in good agreement with both the Bishop-Hill theory and the experimental results. Influenced by the tube geometry, the instability strains at the onset of diffuse necking are decreased by an increase in hoop tension. The diffuse necking strains are reasonably predicted by the Swift and the LankfordSaibel/Mellor criteria.

  19. Biaxial Yield Surface Investigation of Polymer-Matrix Composites

    Directory of Open Access Journals (Sweden)

    Zhengjia He

    2013-03-01

    Full Text Available This article presents a numerical technique for computing the biaxial yield surface of polymer-matrix composites with a given microstructure. Generalized Method of Cells in combination with an Improved Bodner-Partom Viscoplastic model is used to compute the inelastic deformation. The validation of presented model is proved by a fiber Bragg gratings (FBGs strain test system through uniaxial testing under two different strain rate conditions. On this basis, the manufacturing process thermal residual stress and strain rate effect on the biaxial yield surface of composites are considered. The results show that the effect of thermal residual stress on the biaxial yield response is closely dependent on loading conditions. Moreover, biaxial yield strength tends to increase with the increasing strain rate.

  20. Design optimization of cruciform specimens for biaxial fatigue loading

    OpenAIRE

    R. Baptista,; R. A. Claudio; L. Reis,; I. Guelho,; de Freitas, M.; Madeira, J. F. A.

    2014-01-01

    In order to correctly assess the biaxial fatigue material properties one must experimentally test different load conditions and stress levels. With the rise of new in-plane biaxial fatigue testing machines, using smaller and more efficient electrical motors, instead of the conventional hydraulic machines, it is necessary to reduce the specimen size and to ensure that the specimen geometry is appropriated for the load capacity installed. At the present time there are no standard sp...

  1. Biaxial Creep Specimen Fabrication

    International Nuclear Information System (INIS)

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

  2. Biaxial Creep Specimen Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    JL Bump; RF Luther

    2006-02-09

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

  3. Light propagation in biaxial crystals

    CERN Document Server

    Turpin, Alex; Kalkandjiev, Todor K; Mompart, Jordi

    2015-01-01

    We present a formalism able to predict the transformation of light beams passing through biaxial crystals. We use this formalism to show both theoretically and experimentally the transition from double refraction to conical refraction, which is found when light propagates along one of the optic axes of a biaxial crystal. Additionally, we demonstrate that the theory is applicable both to non-cylindrically symmetric and non-homogeneously polarized beams by predicting the transformation of input beams passing through a cascade of biaxial crystals.

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

    Science.gov (United States)

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

    1997-01-01

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

  5. Post-buckling capacity of bi-axially loaded rectangular steel plates

    DEFF Research Database (Denmark)

    Jönsson, Jeppe; Bondum, T. H.

    2012-01-01

    Results from a detailed numerical investigation of the post-buckling behaviour of rectangular simply supported steel plates subjected to biaxial in-plane loading are presented. The Steel plates are loaded through forced edge displacements. The effects of initial imperfections, aspect ratio, plate slenderness and edge displacement ratio are included in the investigations presented. Capacity interaction curves are established in the bi-axial stress domain. It turns out that for certain stress ratios the imperfections dominating the ultimate capacity are not affine to the lowest classical buckling mode for biaxial stress. It is of great interest that short wave imperfections of a lower magnitude compared to conventionally used imperfections are seen to lower the capacity of the bi-axially loaded plates. The topic is of major concern in the flange plates of long span bridges with multi box girder configurations.

  6. Residual stress fields in surface-treated silicon carbide for space industry--comparison of biaxial and triaxial analysis using different X-ray methods

    International Nuclear Information System (INIS)

    Any mechanical surface treatment and machining leaves 'footprints' in the form of residual stress fields in the surface region of technical parts or components, which are detectable by X-ray diffraction. In the present paper, we applied different X-ray methods to investigate the residual stress state in the near-surface zone of sintered silicon carbide after mechanical surface processing. Using the sin2 ?-based 'universal plot' method, we found steep gradients for the in-plane components ?11 and ?22 in the form of high compressive stresses at the surface, which change into tensile stresses within a few microns. To gain information on the triaxial residual stress state, we applied the scattering vector method, which is based on strain depth profiling by sample rotation around the diffraction vector. For the in-plane stresses, we observed gradients similar to those obtained by the 'universal plot' method, but they were shifted on the absolute scale towards tensile stress. We explain this difference by 'pseudo-macroscopic' tensile residual stress fields ?33, which act normal to the surface and therefore pretend higher in-plane compressive stresses ?ii (i = 1, 2), if they are not regarded in the evaluation procedure

  7. Crack under biaxial loading: Two-parameter description.

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Bermejo, C. S.

    Ostrava : VŠB Ostrava, 2014 - (Krejsa, M.), s. 1-6 ISBN 978-80-248-3320-0. [Modelování v mechanice 2014. Ostrava (CZ), 05.02.2014-06.02.2014] R&D Projects: GA ?R(CZ) GAP105/11/1551 Institutional support: RVO:68081723 Keywords : Biaxial loading * T- stress * stress intensity factor * crack Subject RIV: JL - Materials Fatigue, Friction Mechanics

  8. Chirality and Biaxiality in Cholesteric Liquid Crystals

    OpenAIRE

    Dhakal, Subas; Selinger, Jonathan V.

    2010-01-01

    We investigate the statistical mechanics of chirality and biaxiality in liquid crystals through a variety of theoretical approaches, including Monte Carlo simulations, lattice mean-field theory, and Landau theory. All of these calculations show that there is an important interaction between cholesteric twist and biaxial order: The twist acts as a field on the biaxial order, and conversely, the biaxial order increases the twist, i.e. reduces the pitch. We model the behavior o...

  9. 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)

  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 testing of canine annulus fibrosus tissue under changing salt concentrations

    OpenAIRE

    Jacques M. Huyghe

    2010-01-01

    The in vivo mechanics of the annulus fibrosus of the intervertebral disc is one of biaxial rather than uniaxial loading. The material properties of the annulus are intimately linked to the osmolarity in the tissue. This paper presents biaxial relaxation experiments of canine annulus fibrosus tissue under stepwise changes of external salt concentration. The force tracings show that stresses are strongly dependent on time, salt concentration and orientation. The force tracing signature of are s...

  12. Volume phase transitions of biaxial nematic elastomers.

    Science.gov (United States)

    Matsuyama, Akihiko

    2012-01-01

    We present a mean-field theory to describe biaxial nematic phases of side-chain liquid crystalline elastomers. Novel biaxial nematic phases are theoretically predicted in a side-chain liquid crystalline polymer and gel, where side chains (mesogens) and rigid-backbone chains favor mutually perpendicular orientations. We calculate uniaxial and biaxial orientational order parameters and examine deformations of the gel and stable biaxial nematic phases of the liquid crystalline gel dissolved in isotropic solvents. We predict first-order uniaxial-biaxial nematic phase transitions of the gel and the volume of the gel is discontinuously changed at the phase transition temperature. PMID:22400583

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

    OpenAIRE

    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 failu...

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

    Science.gov (United States)

    Becker, Winston R; De Vita, Raffaella

    2015-06-01

    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

  16. 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.

  17. Biaxially oriented film on flexible polymeric substrate

    Science.gov (United States)

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

    2009-10-13

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

  18. Biaxial shear/tension failure criteria of spectra single fibers

    Science.gov (United States)

    Sun, Jianzhuo

    An experimental study was conducted to develop the biaxial failure surface criteria of single Spectra 130d and 100d filaments in a torsion-tension environment. The cross-sectional profiles of single Spectra fibers were investigated using scanning electron microscopy and X-ray computed tomography. A pin-gripping method to fix the ends of a polyethylene single fiber was developed. Effects of pin diameter on failure stress for both Spectra 130d and 100d were characterized. It was found that the perturbed stress field effect can be neglected when the pin diameter is larger than 0.8 mm. Additionally, the effect of the sample's gage length on fiber tensile strength was investigated. The gage length of 5.5 mm was determined as an appropriate length for single fiber samples under stress-wave loading. A twisting apparatus was built for a single fiber to achieve specific degrees of shear strains. Quasi-static experiments were conducted using an MTS servo-hydraulic system to apply tensile loads on pre-twisted Spectra fibers. A tension Kolsky bar was employed to study the biaxial shear/tensile behavior of Spectra fibers at high strain rates. A decreasing trend of tensile strength, with increasing torsional strain, for Spectra fibers was observed. Furthermore, a torsional pendulum apparatus was developed to determine the torsional shear stresses in fibers at various levels of axial loading. The relationship between apparent shear stress and axial stress was discovered. Finally, a biaxial shear/tension failure criterion envelope of each of the Spectra fibers was established. Scanning electron microscopy images revealed the specific feature on the surface of twisted fibers and fracture surface of failure fibers.

  19. Biaxial fatigue of mild steel; data compilation and analysis

    International Nuclear Information System (INIS)

    This paper describes a study performed at the University of Waterloo which combined data from nine investigations of fatigue of mild steels at room temperature under fully-reversed, biaxial, stress or strain controlled, conditions. This assemblage of some 260 data points covers the fatigue life range from 10 to 107 cycles. Biaxial stress ratios, from equibiaxial (+1) to torsional (-1) are represented. By combining data a broad view of the effect of biaxiality on fatigue is obtained. Areas where data are scant or show inconsistencies become apparent and conclusions drawn have more general applicability than those based on a single investigation. The data analyzed are published as amplitude or range of stress, total strain, plastic strain or equivalent plastic strain. A variety of testing techniques and interpretations of specimen failure were used. The chemical composition and heat treatment of the steels used also varied. The paper shows how some standard and other less usual strain based criteria describe the data. Two-part criteria were investigated in which the equivalent elastic and plastic strain components are based on either octahedral - or maximum -shear strain with the equivalent plastic strain modified to include a hydrostatic stress effect. The collected data were also compared to the ASME Pressure Vessel Code curves for design against fatigue. The safety factors included are shown to be less than the desired 2 on stress or 20 on life particularlired 2 on stress or 20 on life particularly at short fatigue lives. Some modifications to the design practice to restore these safety factors are suggested

  20. 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

  1. Singular values, nematic disclinations, and emergent biaxiality.

    Science.gov (United States)

    ?opar, Simon; Dennis, Mark R; Kamien, Randall D; Žumer, Slobodan

    2013-05-01

    Both uniaxial and biaxial nematic liquid crystals are defined by orientational ordering of their building blocks. While uniaxial nematics only orient the long molecular axis, biaxial order implies local order along three axes. As the natural degree of biaxiality and the associated frame that can be extracted from the tensorial description of the nematic order vanishes in the uniaxial phase, we extend the nematic director to a full biaxial frame by making use of a singular value decomposition of the gradient of the director field instead. The degrees of freedom are unveiled in the form of quasidefects and the similarities and differences between the uniaxial and biaxial phase are analyzed by applying the algebraic rules of the quaternion group to the uniaxial phase. PMID:23767474

  2. Peripheral shear strength of biaxially tensioned reinforced concrete wall elements

    International Nuclear Information System (INIS)

    The results of a series of tests on biaxially tensioned, orthogonally reinforced concrete panels subjected to punching shear are presented and discussed. Contrary to existing U.S. code provisions, the punching shear capacity is not reduced significantly as the biaxial tension level is increased to as much as 0,8fsub(y) in the reinforcement. A design equation is proposed that gives 4?f'sub(c) shear stress for zero biaxial tension and a linear decrease to 3.1?f'sub(c) as the tension is increased to 0.9fsub(y). The size of the loading pad under the punching force and the shear span have little effect on the strength but the pattern of the failure crack does change with these geometric variables. The splitting crack tends to connect the edge of the loading pad and the supports. More testing is recommended to evaluate a few additional variables, such as the use of inserts which receive the punching force. (orig.)

  3. 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

  4. Biaxial mechanical testing of posterior sclera using high-resolution ultrasound speckle tracking for strain measurements.

    Science.gov (United States)

    Cruz Perez, Benjamin; Tang, Junhua; Morris, Hugh J; Palko, Joel R; Pan, Xueliang; Hart, Richard T; Liu, Jun

    2014-03-21

    This study aimed to characterize the mechanical responses of the sclera, the white outer coat of the eye, under equal-biaxial loading with unrestricted shear. An ultrasound speckle tracking technique was used to measure tissue deformation through sample thickness, expanding the capabilities of surface strain techniques. Eight porcine scleral samples were tested within 72 h postmortem. High resolution ultrasound scans of scleral cross-sections along the two loading axes were acquired at 25 consecutive biaxial load levels. An additional repeat of the biaxial loading cycle was performed to measure a third normal strain emulating a strain gage rosette for calculating the in-plane shear. The repeatability of the strain measurements during identical biaxial ramps was evaluated. A correlation-based ultrasound speckle tracking algorithm was used to compute the displacement field and determine the distributive strains in the sample cross-sections. A Fung type constitutive model including a shear term was used to determine the material constants of each individual specimen by fitting the model parameters to the experimental stress-strain data. A non-linear stress-strain response was observed in all samples. The meridian direction had significantly larger strains than that of the circumferential direction during equal-biaxial loadings (P'stracking for strain measurements during mechanical testing. PMID:24438767

  5. Biaxial tensile testing and constitutive modeling of human supraspinatus tendon.

    Science.gov (United States)

    Szczesny, Spencer E; Peloquin, John M; Cortes, Daniel H; Kadlowec, Jennifer A; Soslowsky, Louis J; Elliott, Dawn M

    2012-02-01

    The heterogeneous composition and mechanical properties of the supraspinatus tendon offer an opportunity for studying the structure-function relationships of fibrous musculoskeletal connective tissues. Previous uniaxial testing has demonstrated a correlation between the collagen fiber angle distribution and tendon mechanics in response to tensile loading both parallel and transverse to the tendon longitudinal axis. However, the planar mechanics of the supraspinatus tendon may be more appropriately characterized through biaxial tensile testing, which avoids the limitation of nonphysiologic traction-free boundary conditions present during uniaxial testing. Combined with a structural constitutive model, biaxial testing can help identify the specific structural mechanisms underlying the tendon's two-dimensional mechanical behavior. Therefore, the objective of this study was to evaluate the contribution of collagen fiber organization to the planar tensile mechanics of the human supraspinatus tendon by fitting biaxial tensile data with a structural constitutive model that incorporates a sample-specific angular distribution of nonlinear fibers. Regional samples were tested under several biaxial boundary conditions while simultaneously measuring the collagen fiber orientations via polarized light imaging. The histograms of fiber angles were fit with a von Mises probability distribution and input into a hyperelastic constitutive model incorporating the contributions of the uncrimped fibers. Samples with a wide fiber angle distribution produced greater transverse stresses than more highly aligned samples. The structural model fit the longitudinal stresses well (median R(2) ? 0.96) and was validated by successfully predicting the stress response to a mechanical protocol not used for parameter estimation. The transverse stresses were fit less well with greater errors observed for less aligned samples. Sensitivity analyses and relatively affine fiber kinematics suggest that these errors are not due to inaccuracies in measuring the collagen fiber organization. More likely, additional strain energy terms representing fiber-fiber interactions are necessary to provide a closer approximation of the transverse stresses. Nevertheless, this approach demonstrated that the longitudinal tensile mechanics of the supraspinatus tendon are primarily dependent on the moduli, crimp, and angular distribution of its collagen fibers. These results add to the existing knowledge of structure-function relationships in fibrous musculoskeletal tissue, which is valuable for understanding the etiology of degenerative disease, developing effective tissue engineering design strategies, and predicting outcomes of tissue repair. PMID:22482671

  6. Design optimization of cruciform specimens for biaxial fatigue loading

    Directory of Open Access Journals (Sweden)

    R. Baptista

    2014-10-01

    Full Text Available In order to correctly assess the biaxial fatigue material properties one must experimentally test different load conditions and stress levels. With the rise of new in-plane biaxial fatigue testing machines, using smaller and more efficient electrical motors, instead of the conventional hydraulic machines, it is necessary to reduce the specimen size and to ensure that the specimen geometry is appropriated for the load capacity installed. At the present time there are no standard specimen’s geometries and the indications on literature how to design an efficient test specimen are insufficient. The main goal of this paper is to present the methodology on how to obtain an optimal cruciform specimen geometry, with thickness reduction in the gauge area, appropriated for fatigue crack initiation, as a function of the base material sheet thickness used to build the specimen. The geometry is optimized for maximum stress using several parameters, ensuring that in the gauge area the stress is uniform and maximum with two limit phase shift loading conditions. Therefore the fatigue damage will always initiate on the center of the specimen, avoiding failure outside this region. Using the Renard Series of preferred numbers for the base material sheet thickness as a reference, the reaming geometry parameters are optimized using a derivative-free methodology, called direct multi search (DMS method. The final optimal geometry as a function of the base material sheet thickness is proposed, as a guide line for cruciform specimens design, and as a possible contribution for a future standard on in-plane biaxial fatigue tests.

  7. 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

  8. Molecular field theory for biaxial smectic A liquid crystals.

    Science.gov (United States)

    To, T B T; Sluckin, T J; Luckhurst, G R

    2013-10-01

    Thermotropic biaxial nematic phases seem to be rare, but biaxial smectic A phases less so. Here we use molecular field theory to study a simple two-parameter model, with one parameter promoting a biaxial phase and the second promoting smecticity. The theory combines the biaxial Maier-Saupe and McMillan models. We use alternatively the Sonnet-Virga-Durand (SVD) and geometric mean approximations (GMA) to characterize molecular biaxiality by a single parameter. For non-zero smecticity and biaxiality, the model always predicts a ground state biaxial smectic A phase. For a low degree of smectic order, the phase diagram is very rich, predicting uniaxial and biaxial nematic and smectic phases, with the addition of a variety of tricritical and tetracritical points. For higher degrees of smecticity, the region of stability of the biaxial nematic phase is restricted and eventually disappears, yielding to the biaxial smectic phase. Phase diagrams from the two alternative approximations for molecular biaxiality are similar, except inasmuch that SVD allows for a first-order isotropic-biaxial nematic transition, whereas GMA predicts a Landau point separating isotropic and biaxial nematic phases. We speculate that the rarity of thermotropic biaxial nematic phases is partly a consequence of the presence of stabler analogous smectic phases. PMID:24116580

  9. 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.

  10. Vertically aligned biaxially textured molybdenum thin films

    International Nuclear Information System (INIS)

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

  11. Vertically aligned biaxially textured molybdenum thin films

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-09-15

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

  12. 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).

  13. 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.

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

    OpenAIRE

    Bru?ggenwirth, Martin; Fricke, Heiko; Knoche, Moritz

    2014-01-01

    Sweet cherry and other fleshy fruit crack when the surface is exposed to water. Osmotic water uptake is believed to increase fruit volume and hence surface area, thereby subjecting the skin to stress and strain. The objectives were to (1) establish a standardized biaxial tensile test that simulates the in vivo strain of the skin and (2) characterize its mechanical properties. A bulging device was used to pressurize skin segments. Pressure and extent of bulging were monitored. The data demonst...

  15. Effect of biaxial loading on the fracture behaviour of a ferritic steel component

    International Nuclear Information System (INIS)

    The effect of biaxial loading on the ductile tearing behaviour of a through-wall crack in a ferritic steel structure under contained yield is of particular interest to the structural integrity argument for reactor pressure vessels. This results from the fact that there are many instances in practice, (for example a crack in a circumferential weld), where a significant applied stress is present in the direction parallel to the crack as well as in the perpendicular direction. Two large plate ductile tearing tests have been performed on centre through-crack specimens (75 mm by 2 m by 2 m) manufactured from a ferritic steel. The first test specimen was loaded in uniaxial tension and the second test specimen was loaded bi-axially. This paper presents experimental details and results of the two wide plate tests and describes the analysis work being undertaken which is required to interpret the experiments satisfactorily. Preliminary results of this analysis work are presented. The following main conclusions may be drawn from the work contained in this report: 1) The initiation applied stress, evaluated by the ACPD method, for the biaxial specimen, GNSR/1.OB, was approximately 20% higher than that for the uniaxial specimen, GNSR/1.OU indicating an effective benefit of biaxial loading. 2) The maximum applied stresses were similar in the two tests with that for the biaxial test being slightly higher than that for the uniaxial test; 106.7 MPa in GNSR/1.OU for 5.3 mm of tearing .7 MPa in GNSR/1.OU for 5.3 mm of tearing and 108.7 MPa in GNSR/1.OB for 3.2 mm of tearing. 3) All the R6 results conservatively under-predicted the applied load for the amounts of ductile tearing obtained in the tests (i.e. 3.5 mm and 5.3 mm in GNSR/1.OU and 3.2 mm and 1.3 mm in GNSR/1.OB). 4) For the GNSR/1.OU bottom crack tip and both crack tips in GNSR/1.OB, it would seem likely that the conservatism would still apply even if the cracks had been grown up to instability. However, for the GNSR/1.OU top crack tip, it is likely that the R6 results would be non-conservative for crack extensions of a few millimetres more than was obtained at that crack tip in the test. 5) Preliminary elastic-plastic finite element analyses carried out for the test plate designs have shown that the effect of the biaxial loading is to reduce the J-Integral values from the uniaxially loaded case of GNSR/1.OU

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

    Science.gov (United States)

    Kuang, Qian-Wei; Liu, Hong-Xia; Wang, Shu-Long; Qin, Shan-Shan; Wang, Zhi-Lin

    2011-12-01

    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.

  17. 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.

  18. Biaxial crystal as a versatile mode converter

    International Nuclear Information System (INIS)

    The extreme versatility of the internal conical refraction in biaxial crystals in the transformation of Gaussian laser beams is demonstrated and discussed. By means of simple variations in the focusing and polarization of the input beam, various beam configurations like Bessel–Gauss, Hermite–Gauss, Laguerre–Gauss, and others are shown to be produced from a lowest-order Gaussian beam passed through a biaxial crystal along one of its optical axes. Further transformations of the beam profile and formation of more complex light patterns were obtained in a cascaded scheme, when the beam was passed consecutively through two crystals. These observations, together with the known ability of conical refraction to form a variety of other complex light structures, demonstrate the unique properties of the effect in manipulations with the amplitude, phase, and polarization of light beams

  19. Biaxial Testing of 2195 Aluminum Lithium Alloy Using Cruciform Specimens

    Science.gov (United States)

    Johnston, W. M.; Pollock, W. D.; Dawicke, D. S.; Wagner, John A. (Technical Monitor)

    2002-01-01

    A cruciform biaxial test specimen was used to test the effect of biaxial load on the yield of aluminum-lithium alloy 2195. Fifteen cruciform specimens were tested from 2 thicknesses of 2195-T8 plate, 0.45 in. and 1.75 in. These results were compared to the results from uniaxial tensile tests of the same alloy, and cruciform biaxial tests of aluminum alloy 2219-T87.

  20. Creep Buckling Of Plates Under Biaxial Compression

    OpenAIRE

    Ashour, H. A.

    1992-01-01

    This work presents an analysis for the creep buckling problem of geometrically imperfect rectangular flat plates under biaxial compression with simple support boundary conditions. The analysis is based on a non-dimensional form of Donnell-type equations for a slightly imperfect flat plate. The elastic constitutive equations for a thin plate are employed. The basic elastic equilibrium equations in the middle surface displacement components are derived through the employment of the principle of...

  1. Defect morphology in a biaxial thermotropic polymer

    OpenAIRE

    De'Neve, T.; Kleman, M.; Navard, P.

    1992-01-01

    Optical observations of the thread texture of a nematic thermotropic polymer commercially known as VECTRA B950 have shown the existence of three types of half integer disclination lines, called here Ex, Ey and Ez, sometimes associated with integer disclination lines. This plurality of defects is typical of the biaxial nature of this nematic phase, due to interchain rotational correlations between phenyl rings. The relationships between defects which arise from the topological theory are confi...

  2. Biaxial crystal-based optical tweezers

    DEFF Research Database (Denmark)

    Angelsky, Oleg V.; Maksimyak, Andrew P.

    2010-01-01

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

  3. Investigation of in-plane biaxial low cycle fatigued austenitic stainless steel AISI 321. I. Mechanical testing on the planar biaxial load machine

    International Nuclear Information System (INIS)

    During fatigue loading of structural materials such as stainless steel, changes in the microstructure which affect the mechanical and physical properties occur. Experimental simulation of the loading conditions that induce the changes can be performed by mechanical loading, usually in the form of uniaxial tension-compression cycling. However, real machines and structures are subjected to more complex multiaxial stresses. Fatigue and fracture under multiaxial stresses are one of the most important current topics aimed at ensuring improved reliability of industrial components. The first step towards better understanding of this problem is to subject the materials to biaxial loading. The material examined was low austenitic stainless steel AISI 321 H. A set of the four samples of cruciform geometry was subjected to the biaxial tension-compression fatigue cycling with the frequency of 0.5 Hz at the applied load of 10-17 kN. The samples are intended for the neutron diffraction measurements of the residual stresses and the mechanical characterizations on a dedicated stress-diffractometer

  4. 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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2014-04-01

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

  7. Modelizing ratcheting in biaxial tests

    International Nuclear Information System (INIS)

    A new constitutive equation has been developed on a purely phenomenological basis in order to interpret ratcheting experiments. The model is based on a generalized Arsmstrong-Frederick equation for the kinematic variable; the coefficients of this equation are functions of both instantaneous and accumulated plastic strain. The experiments described relate to austenitic stainless steel (17-12 SPH) tubular specimens subjected to cyclic torsional loading under constant tensile stress at 600 deg C. Comparisons between experimental and theoretical results show that the model reasonably well predicts not only ratcheting but also hysteresis loops and the cyclic hardening curve

  8. Effect of biaxial loading on the fracture behavior of a ferritic steel component

    International Nuclear Information System (INIS)

    The effect of biaxial loading on the ductile tearing behaviour of a through-wall crack in a ferritic steel structure under contained yield is of particular interest to the structural integrity argument for reactor pressure vessels. This results from the fact that there are many instances in practice, (for example a crack in a circumferential weld), where a significant applied stress is present in the direction parallel to the crack as well as in the perpendicular direction. Two large plate ductile tearing tests have been performed on center through-crack specimens (75 mm by 2 m by 2 m) manufactured from a ferritic steel. The first test specimen was loaded in uniaxial tension and the second test specimen was loaded biaxially. This paper presents experimental details and results of the two wide plate tests and describes the analysis work being undertaken which is required to interpret the experiments satisfactorily. Preliminary results of this analysis work are presented. 2 refs., 19 figs

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

    Directory of Open Access Journals (Sweden)

    M. N. Saraf

    1990-04-01

    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.

  10. 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

  11. 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.

  12. Biaxially textured articles formed by powder metallurgy

    Science.gov (United States)

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

    2005-06-07

    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. Biaxially textured articles formed by power metallurgy

    Science.gov (United States)

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

    2003-08-26

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

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

    International Nuclear Information System (INIS)

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

  15. 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

  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. 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

  18. 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.

  19. High temperature creep damage under biaxial loading: INCO 718 and 316 (17-12 SPH) steels

    International Nuclear Information System (INIS)

    The respective influence of the Von-Mises equivalent stress and of the maximum principal stress on high temperature creep damage of two industrial alloys (INCO 718 and 17-12 SPH stainless steel) are pointed out in a quantitative way through tensile-torsion biaxial tests. Through inversions of the shear component, the important part taken by the principal direction corresponding to the maximum principal stress is also shown. The results are observed to be opposite according to whether the alloy suffers cyclic hardening as 17-12 SPH does or cyclic softening which is the case of Inco 718. These results are supported by metallographic observations. They demand an anisotropic form for the damage variable D, while besides a time dependence, the kinetic equation must include the part taken by the strain

  20. Novel biaxial nematic phases of side-chain liquid crystalline polymers.

    Science.gov (United States)

    Matsuyama, Akihiko

    2012-12-14

    We present a mean field theory to describe biaxial nematic phases of side-chain liquid crystalline polymers, in which rigid side-chains (mesogens) and rigid-backbone chains favor mutually perpendicular orientations. Taking into account both excluded volume and attractive interactions between rigid rods, novel biaxial nematic phases are theoretically predicted. We calculate uniaxial and biaxial orientational order parameters as a function of temperature and the length of backbone chains. We find a first-order biaxial-biaxial phase transition and a first (or second)-order uniaxial-biaxial one, depending on the length of mesogens and backbone chains. PMID:23249031

  1. Biaxial Tensile Test of Cold Rolled IF Steel Sheet for Large Plastic Strain Range

    Science.gov (United States)

    Enatsu, Ryotaro; Kuwabara, Toshihiko

    2011-08-01

    Deformation behavior of cold rolled IF steel sheet (SPCE) under biaxial tension has been investigated for large plastic strain range over 15%. The test material was bent and TIG welded to form a tubular specimen with an outer diameter of 46.2 mm and wall thickness of 0.8 mm. The tubular specimens have been subjected to linear stress paths in the first quadrant of stress space with the use of a servo-controlled tension-internal pressure testing machine developed by one of the authors [T. Kuwabara, K. Yoshida, K. Narihara, S. Takahashi, Anisotropic plastic deformation of extruded aluminum alloy tube under axial forces and internal pressure, Int. J. Plasticity 21, 101-117 (2005)]. Moreover, biaxial tensile tests using a cruciform specimen have also been carried out to more precisely measure the deformation behavior for a small strain range following initial yielding. True stress-true plastic strain curves, contours of plastic work in stress space and the directions of plastic strain rates have been measured and compared with those calculated using selected yield functions: the von Mises, Hill's quadratic and Yld2000-2d [Barlat, F., Brem, J.C., Yoon, J.W., Chung, K., Dick, R.E., Lege, D.J., Pourboghrat, F., Choi, S.H., Chu, E., Plane stress yield function for aluminum alloy sheets—Part 1: Theory. Int. J. Plasticity 19, 1297-1319 (2003)]. The plastic deformation behavior up to a work equivalent plastic strain of ?0p = 0.19 has been successfully measured. It is found that the test material exhibits differential hardening and that the Yld2000-2d yield function with an exponent of six most closely predicts the contours of plastic work and the directions of plastic strain rates.

  2. 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.

  3. Defect morphology in a biaxial thermotropic polymer

    Science.gov (United States)

    de'Neve, T.; Kleman, M.; Navard, P.

    1992-02-01

    Optical observations of the thread texture of a nematic thermotropic polymer commercially known as VECTRA B950^{circledR} have shown the existence of three types of half integer disclination lines, called here Ex, Ey and Ez, sometimes associated with integer disclination lines. This plurality of defects is typical of the biaxial nature of this nematic phase, due to interchain rotational correlations between phenyl rings. The relationships between defects which arise from the topological theory are confirmed, in static as well as in dynamic experiments. During shear flow, there is a splitting of Ey into Ex and Ez at a shear deformation lower than that corresponding to the multiplication of Ex and Ez defects. Les observations optiques de la texture à fils d'un polymère thermotrope nématique, commercialisé sous la référence VECTRA B950^{circledR}, ont montré l'existence de trois types de lignes de disinclinaisons, appelées ici Ex, Ey et Ez, de rang demi-entier, parfois associées à des lignes entières. La pluralité de ces défauts est caractéristique de la nature de cette phase nématique biaxe, reliée à des corrélations de rotation interchaînes entre les plans aromatiques. Les relations topologiques entre défauts caractéristiques de la phase biaxe sont vérifiées dans les situations statiques aussi bien que dynamiques. Durant un écoulement de cisaillement, il ya une séparation de Ey en Ex et Ez, à une déformation plus petite que celle correspondant à la multiplication des défauts Ex et Ez.

  4. Light Scattering Study of Biaxiality in Nematic Liquid Crystal Tetrapodes

    Science.gov (United States)

    Neupane, Krishna; Kang, Shinwoong; Sharma, Sunil; Carney, D.; Meyer, T.; Mehl, George H.; Allender, David W.; Kumar, Satyendra; Sprunt, Samuel

    2008-03-01

    We have performed dynamic light scattering studies on thermotropic liquid crystalline tetrapodes [1], which reportedly exhibit a uniaxial to biaxial nematic phase transition. Our results [2] support the existence of the biaxial nematic phase in tetrapodes. The uni - to biaxial transition is found to be weakly first-order in a 4-ring tetrapode and second-order in a 3-ring tetrapode, while the isotropic to uniaxial nematic transition is weakly first order in both materials. The temperature dependence of the relaxation rates of the biaxial order parameter modes, and of the intensity associated with biaxial director fluctuations, is explained by a Landau-deGennes model of the free energy. [1] R. Elsasser, J. W. Goodby, G. H. Mehl, D. Rodriguez-Martin, R. M. Richardson, D. J. Photinos, and M. Veith, Mol. Cryst. Liq. Cryst. 402, 237 (2003) [2] K. Neupane, S. W. Kang, S. Sharma, D. Carney, T. Meyer, G. H. Mehl, D. W. Allender, S. Kumar, and S. Sprunt, Phys. Rev. Lett. 97, 207802 (2006)

  5. 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.

  6. Field response and switching times in biaxial nematics.

    Science.gov (United States)

    Berardi, Roberto; Muccioli, Luca; Zannoni, Claudio

    2008-01-14

    We study by means of virtual molecular dynamics computer experiments the response of a bulk biaxial nematic to an applied external field and, in particular, the relative speed of reorientation of the principal director axis and of the secondary one, typical of these new materials, upon a pi2 field switch. We perform the simulations setting up and integrating the equations of motion for biaxial Gay-Berne particles using quaternions and a suitable time reversible symplectic integrator. We find that switching of the secondary axis is up to an order of magnitude faster than that of the principal axis, and that under fields above a certain strength a reorganization of local domains, temporarily disrupting the nematic and biaxial ordering, rather than a collective concerted reorientation occurs. PMID:18205473

  7. 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

  8. 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.

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

    Science.gov (United States)

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

    2014-05-01

    We investigate the phase sequence of biaxial liquid crystals, based on a general quadratic model Hamiltonian over the relevant parameter space, with a Monte Carlo simulation which constructs equilibrium ensembles of microstates, overcoming possible (free) energy barriers (combining entropic and frontier sampling techniques). The resulting phase diagram qualitatively differs from the universal phase diagram predicted earlier from mean-field theory (MFT), as well as the Monte Carlo simulations with the Metropolis algorithm. The direct isotropic-to-biaxial transition predicted by the MFT is replaced in certain regions of the space by the onset of an additional intermediate biaxial phase of very low order, leading to the sequence N(B)-N(B1)-I. This is due to inherent barriers to fluctuations of the components comprising the total energy, and may explain the difficulties in the experimental realization of these phases. PMID:25353730

  10. Alloy composition dependency of plastic deformation behavior in biaxial compressions of Ti-Nb alloys

    Science.gov (United States)

    Shimizu, Ichiro; Hisada, Kazuki; Ishikawa, Shinichi; Takemoto, Yoshito; Tada, Naoya

    2015-03-01

    Crystal structure of titanium alloy changes from alpha (hexagonal close-packed) to beta (body centered cubic) with increase of beta stabilizer content. This change of structure strongly influences on the plastic deformation behavior of titanium alloys, because it not only induces changes of slip systems but also activates martensitic transformation and deformation twinning. However, most of past studies on titanium alloys have been focused on the development of specific functionalities induced by alloy designing, and few research works have been reported on metal workability under multi-axial stress conditions, which is key factor to apply titanium alloys for engineering products. In this study, uniaxial and biaxial compression tests of titanium-niobium alloys with various niobium contents have been performed to clarify the influence of beta stabilizer content on the plastic behavior under compressive stress conditions. The titanium-niobium alloys were solution treated and then quenched from beta region to obtain metastable structures. The resultant stress-strain relations together with microscopic observations of texture revealed that the influence of niobium contents on the predominant plastic deformation mechanisms and thus on the hardening phenomena. The equi-plastic work contours obtained by uniaxial and biaxial compression tests also implied the crystal structure dependency of anisotropic hardening, which was evaluated quantitatively by means of Hill's anisotropic yield criterion. The results will provide information on the versatile constitutive relations of titanium alloys containing beta stabilizer elements, that is important to prove the performance of products manufactured by compressive metal working processes such as forging and extrusion.

  11. Biaxial testing of canine annulus fibrosus tissue under changing salt concentrations

    Scientific Electronic Library Online (English)

    Jacques M., Huyghe.

    2010-03-01

    Full Text Available A mecânica in vivo do anel fibroso do disco intervertebral é baseada em carregamento biaxial ao invés de uniaxial. As propriedades materiais do anel estão intimamente ligadas à osmolaridade no tecido. O artigo apresenta experimentos de relaxação biaxiais do anel fibroso de um tecido canino sob mudan [...] ças abruptas na concentração externa de sal. A assinatura da força devido à mudança brusca de salinidade resulta em uma progressiva e monótona mudança na tensão em direção a um novo valor de equilíbrio. Embora o número de amostras não permita nenhuma conclusão quantitativa, as tendências podem abrir uma luz no entendimento das interações complexas na direção das forças, deformações e orientação das fibras por um lado e a osmolaridade do tecido por outro lado. A resposta dual devido à uma mudança na deformação é compreendida como uma resposta imediata antes do fluido escoar para dentro ou para fora do tecido, seguido de uma progressiva readaptação da quantidade de fluido notempo devido ao gradiente do potencial químico entre o tecido e a solução externa. Abstract in english The in vivo mechanics of the annulus fibrosus of the intervertebral disc is one of biaxial rather than uniaxial loading. The material properties of the annulus are intimately linked to the osmolarity in the tissue. This paper presents biaxial relaxation experiments of canine annulus fibrosus tissue [...] under stepwise changes of external salt concentration. The force tracings show that stresses are strongly dependent on time, salt concentration and orientation. The force tracing signature of are sponse to a change instrain, is one of a jumpin stress that relaxes partly as the new strain is maintained. The force tracing signature of a stepwise change in salt concentration is a progressive monotonous change in stress towards a new equilibrium value. Although the number of samples does not allow any definitive quantitative conclusions, the trends may shed light on the complex interaction among the directionality of forces, strains and fiber orientation on one hand, and on the other hand, the osmolarity of the tissue. The dual response to a change in strain is understood as an immediate response before fluid flows in or out of the tissue, followed by a progressive readjustment of the fluid content in time because of the gradient in fluid chemical potential between the tissue and the surrounding solution.

  12. Biaxial testing of canine annulus fibrosus tissue under changing salt concentrations

    Directory of Open Access Journals (Sweden)

    Jacques M. Huyghe

    2010-03-01

    Full Text Available The in vivo mechanics of the annulus fibrosus of the intervertebral disc is one of biaxial rather than uniaxial loading. The material properties of the annulus are intimately linked to the osmolarity in the tissue. This paper presents biaxial relaxation experiments of canine annulus fibrosus tissue under stepwise changes of external salt concentration. The force tracings show that stresses are strongly dependent on time, salt concentration and orientation. The force tracing signature of are sponse to a change instrain, is one of a jumpin stress that relaxes partly as the new strain is maintained. The force tracing signature of a stepwise change in salt concentration is a progressive monotonous change in stress towards a new equilibrium value. Although the number of samples does not allow any definitive quantitative conclusions, the trends may shed light on the complex interaction among the directionality of forces, strains and fiber orientation on one hand, and on the other hand, the osmolarity of the tissue. The dual response to a change in strain is understood as an immediate response before fluid flows in or out of the tissue, followed by a progressive readjustment of the fluid content in time because of the gradient in fluid chemical potential between the tissue and the surrounding solution.A mecânica in vivo do anel fibroso do disco intervertebral é baseada em carregamento biaxial ao invés de uniaxial. As propriedades materiais do anel estão intimamente ligadas à osmolaridade no tecido. O artigo apresenta experimentos de relaxação biaxiais do anel fibroso de um tecido canino sob mudanças abruptas na concentração externa de sal. A assinatura da força devido à mudança brusca de salinidade resulta em uma progressiva e monótona mudança na tensão em direção a um novo valor de equilíbrio. Embora o número de amostras não permita nenhuma conclusão quantitativa, as tendências podem abrir uma luz no entendimento das interações complexas na direção das forças, deformações e orientação das fibras por um lado e a osmolaridade do tecido por outro lado. A resposta dual devido à uma mudança na deformação é compreendida como uma resposta imediata antes do fluido escoar para dentro ou para fora do tecido, seguido de uma progressiva readaptação da quantidade de fluido notempo devido ao gradiente do potencial químico entre o tecido e a solução externa.

  13. Biaxial High Cycle Fatigue of a Type 304L Stainless Steel: Cyclic Strains and Crack Initiation Detection by Digital Image Correlation

    OpenAIRE

    Poncelet, M.; Barbier, G.; Raka, B.; Courtin, S.; Desmorat, R.; Le-roux, J. C.; Vincent, L.

    2010-01-01

    Abstract 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 multis...

  14. 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

  15. Strain Measurement System Developed for Biaxially Loaded Cruciform Specimens

    Science.gov (United States)

    Krause, David L.

    2000-01-01

    A new extensometer system developed at the NASA Glenn Research Center at Lewis Field measures test area strains along two orthogonal axes in flat cruciform specimens. This system incorporates standard axial contact extensometers to provide a cost-effective high-precision instrument. The device was validated for use by extensive testing of a stainless steel specimen, with specimen temperatures ranging from room temperature to 1100 F. In-plane loading conditions included several static biaxial load ratios, plus cyclic loadings of various waveform shapes, frequencies, magnitudes, and durations. The extensometer system measurements were compared with strain gauge data at room temperature and with calculated strain values for elevated-temperature measurements. All testing was performed in house in Glenn's Benchmark Test Facility in-plane biaxial load frame.

  16. 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...

  17. 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.

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

    Science.gov (United States)

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

    2013-01-01

    We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 ?m and a resolution of 20 nm, translating to a positional accuracy of less than 3 ?m over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0.15% to 0.25% full scale. PMID:23644779

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

    OpenAIRE

    Kaloni, T. P.; Cheng, Y. C.; Schwingenschlo?gl, U.

    2013-01-01

    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 doping because of weakening of the 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...

  20. 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

  1. Modelization of ratcheting in biaxial experiments

    International Nuclear Information System (INIS)

    A new constitutive equation has been developed on a purely phenomenological basis in order to interpret ratcheting experiments. The model is based on a generalized Armstrong-Frederick equation for the kinematic variable; the coefficients of this equation are functions of both instantaneous and accumulated plastic strain. The experiments described relate to austenitic stainless steel (17-12 SPH) tubular specimens subjected to cyclic torsional loading under constant tensile stress at 600deg C. Comparisons between experimental and theoretical results show that the model reasonably well predicts not only ratcheting but also hysteresis loops and the cyclic hardening curve. (orig.)

  2. 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

  3. [Stress].

    Science.gov (United States)

    Manso, C F

    1997-04-01

    The general adaptation syndrome is discussed on the light of recent discoveries on hypothalamic peptides and of their possible influence in survival and in induction of diseases. The problem of stress in alcoholism is reviewed. The author ends with a short souvenir of Hans Selye. PMID:9341029

  4. 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.

  5. A soft ellipsoid potential for biaxial molecules : Modeling and computer simulation

    CERN Document Server

    Saha, Jayashree

    2015-01-01

    A soft ellipsoid contact potential model for a pair of biaxial ellipsoidal molecules is proposed which considers the configuration dependent energy anisotropy explicitly along with their geometrical aspects. We performed Molecular Dynamics simulation study to generate both biaxial smectic and nematic phases using this new potential.

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

    Science.gov (United States)

    Cheng, Ron-Bin; Hsu, Su-Yuen

    2012-01-01

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

  7. 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)

  8. The biaxial active mechanical properties of the porcine primary renal artery.

    Science.gov (United States)

    Zhou, Boran; Rachev, Alexander; Shazly, Tarek

    2015-08-01

    The mechanical response of arteries under physiological loads can be delineated into passive and active components. The passive response is governed by the load-bearing constituents within the arterial wall, elastin, collagen, and water, while the active response is a result of vascular smooth muscle cell (SMC) contraction. In muscular blood vessels, such as the primary renal artery, high SMC wall content suggests an elevated importance of the active response in determining overall vessel behavior. This study is a continuation of our previous investigation, in which a four-fiber constitutive model of the passive response of the primary porcine renal artery was identified. Here we focus on the active response of this vessel, specifically in the case of maximal SMC contraction, and develop a constitutive model of the active stress-stretch relations. The results of this study demonstrate the existence of biaxial active stress in the vessel wall, and suggest the active mechanical response is a critical component of renal arterial performance. PMID:25913605

  9. The influence of uniaxial prestrain on biaxial r-values in 7075-O aluminium alloy

    Science.gov (United States)

    Anderson, N.; Brown, D.; McMurray, R. J.; Leacock, A. G.

    2011-05-01

    Biaxial test methods have been used to determine, not only yield behaviour under biaxial conditions, but also the strain response. This paper examines the influence of uniaxial prestrain upon the biaxial r-value by extending the disc compression test procedure proposed by Barlat et al. [1]. The extension involved the use of digital image measurements of in-plane strains. The material examined was a 7075-O condition aluminium alloy. The results of the experimental programme indicated that the biaxial r-value is unaffected by uniaxial prestrain. When using the disc compression test, the mode of deformation and therefore the biaxial r-value were found to be very sensitive to the prevailing friction conditions.

  10. The influence of uniaxial prestrain on biaxial r-values in 7075-O aluminium alloy

    International Nuclear Information System (INIS)

    Biaxial test methods have been used to determine, not only yield behaviour under biaxial conditions, but also the strain response. This paper examines the influence of uniaxial prestrain upon the biaxial r-value by extending the disc compression test procedure proposed by Barlat et al. The extension involved the use of digital image measurements of in-plane strains. The material examined was a 7075-O condition aluminium alloy. The results of the experimental programme indicated that the biaxial r-value is unaffected by uniaxial prestrain. When using the disc compression test, the mode of deformation and therefore the biaxial r-value were found to be very sensitive to the prevailing friction conditions.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-09-01

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

  12. Biaxially stretchable, integrated array of high performance microsupercapacitors.

    Science.gov (United States)

    Lim, By Yein; Yoon, Jangyeol; Yun, Junyeong; Kim, Daeil; Hong, Soo Yeong; Lee, Seung-Jung; Zi, Goangseup; Ha, Jeong Sook

    2014-11-25

    We report on the fabrication of a biaxially stretchable array of high performance microsupercapacitors (MSCs) on a deformable substrate. The deformable substrate is designed to suppress local strain applied to active devices by locally implanting pieces of stiff polyethylene terephthalate (PET) films within the soft elastomer of Ecoflex. A strain suppressed region is formed on the top surface of the deformable substrate, below which PET films are implanted. Active devices placed within this region can be isolated from the strain. Analysis of strain distribution by finite element method confirms that the maximum strain applied to MSC in the strain suppressed region is smaller than 0.02%, while that on the Ecoflex film is larger than 250% under both uniaxial strain of 70% and biaxial strain of 50%. The all-solid-state planar MSCs, fabricated with layer-by-layer deposited multiwalled carbon nanotube electrodes and patterned ionogel electrolyte of poly(ethylene glycol) diacrylate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide having high-potential windows, are dry-transferred onto the deformable substrate and electrically connected in series and parallel via embedded liquid metal interconnection and Ag nanowire contacts. Liquid metal interconnection, formed by injecting liquid metal into the microchannel embedded within the substrate, can endure severe strains and requires no additional encapsulation process. This formed MSC array exhibits high energy and power density of 25 mWh/cm(3) and 32 W/cm(3), and stable electrochemical performance up to 100% uniaxial and 50% biaxial stretching. The high output voltage of the MSC array is used to light micro-light-emitting diode (?-LED) arrays, even under strain conditions. This work demonstrates the potential application of our stretchable MSC arrays to wearable and bioimplantable electronics with a self-powered system. PMID:25347595

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

    Science.gov (United States)

    Kaloni, T. P.; Cheng, Y. C.; Schwingenschlögl, U.

    2013-03-01

    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.

  14. 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.

  15. High magnification crack-tip field characterisation under biaxial conditions

    Directory of Open Access Journals (Sweden)

    B. Moreno

    2013-07-01

    Full Text Available This work presents a novel methodology for characterising fatigue cracks under biaxial conditions. The methodology uses high magnification Digital Image Correlation (DIC technique for measuring displacement and strain crack-tip fields. By applying micro-speckle pattern on the metal surface it is possible to achieve high magnification for DIC technique. The speckles were created by electro-spray technique. The validity of this novel technique is demonstrated by direct comparison with standard extensometer measurements, under tension-compression and torsion conditions. In order to image the correct region, the notch effect on the fatigue life was also evaluated.

  16. Competition between capillarity, layering and biaxiality in a confined liquid crystal.

    Science.gov (United States)

    Varga, S; Martinez-Ratón, Y; Velasco, E

    2010-05-01

    The effect of confinement on the phase behaviour and structure of fluids made of biaxial hard particles (cuboids) is examined theoretically by means of Onsager second-order virial theory in the limit where the long particle axes are frozen in a mutually parallel configuration. Confinement is induced by two parallel planar hard walls (slit-pore geometry), with particle long axes perpendicular to the walls (perfect homeotropic anchoring). In bulk, a continuous nematic-to-smectic transition takes place, while shape anisotropy in the (rectangular) particle cross-section induces biaxial ordering. As a consequence, four bulk phases, uniaxial and biaxial nematic and smectic phases, can be stabilised as the cross-sectional aspect ratio is varied. On confining the fluid, the nematic-to-smectic transition is suppressed, and either uniaxial or biaxial phases, separated by a continuous transition, can be present. Smectic ordering develops continuously from the walls for increasing particle concentration (in agreement with the supression of nematic-smectic second-order transition at confinement), but first-order layering transitions, involving structures with n and n + 1 layers, arise in the confined fluid at high concentration. Competition between layering and uniaxial-biaxial ordering leads to three different types of layering transitions, at which the two coexisting structures can be both uniaxial, one uniaxial and another biaxial, or both biaxial. Also, the interplay between molecular biaxiality and wall interactions is very subtle: while the hard wall disfavours the formation of the biaxial phase, biaxiality is against the layering transitions, as we have shown by comparing the confined phase behaviour of cylinders and cuboids. The predictive power of Onsager theory is checked and confirmed by performing some calculations based on fundamental-measure theory. PMID:20521078

  17. Pressure and Stress Effects on Diffusion in Si

    OpenAIRE

    Aziz, Michael

    1998-01-01

    The thermodynamics of diffusion under hydrostatic pressure and nonhydrostatic stress is presented for single crystals free of extended defects. The thermodynamic relationships obtained permit the direct comparison of hydrostatic and biaxial stress experiments and of atomistic calculations under hydrostatic stress for any proposed mechanism. Atomistic calculations of the volume changes upon point defect formation and migration, and experiments on the effects of pressure and stress on the diffu...

  18. Energy Storage and Dissipation in Random Copolymers during Biaxial Loading

    Science.gov (United States)

    Cho, Hansohl; Boyce, Mary

    2012-02-01

    Random copolymers composed of hard and soft segments in a glassy and rubbery state at the ambient conditions exhibit phase-separated morphologies which can be tailored to provide hybrid mechanical behaviors of the constituents. Here, phase-separated copolymers with hard and soft contents which form co-continuous structures are explored through experiments and modeling. The mechanics of the highly dissipative yet resilient behavior of an exemplar polyurea are studied under biaxial loading. The hard phase governs the initially stiff response followed by a highly dissipative viscoplasticity where dissipation arises from viscous relaxation as well as structural breakdown in the network structure that still provides energy storage resulting in the shape recovery. The soft phase provides additional energy storage that drives the resilience in high strain rate events. Biaxial experiments reveal the anisotropy and loading history dependence of energy storage and dissipation, validating the three-dimensional predictive capabilities of the microstructurally-based constitutive model. The combination of a highly dissipative and resilient behavior provides a versatile material for a myriad of applications ranging from self-healing microcapsules to ballistic protective coatings.

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

    International Nuclear Information System (INIS)

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

  20. 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

  1. 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.

  2. Biaxial Strain Engineering in Suspended MoS2

    Science.gov (United States)

    Lloyd, David; Liu, Xinghui; Cantley, Lauren; Koch, Eric; Yang, Guang; Boddeti, Narasimha; Dunn, Martin L.; Bunch, J. Scott; Bunch Team

    2015-03-01

    Monolayer MoS2 is a direct gap semiconductor and has attracted significant interest for its potential uses in electronics and optoelectronics. It has also been shown to have a highly strain-sensitive bandgap and can sustain strains of up to 11 percent, making it ideally suited for using strain engineering to tune it's electrical and optical properties. Herein, we fabricate pressurized MoS2 blisters using single and few layer MoS2 membranes suspended over cylindrical microcavities. By applying a pressure difference across the membrane and measuring the changes to it's photoluminescence spectrumwe study the effect of elastic biaxial strain engineering on the bandgap of MoS2.

  3. 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.

  4. 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

  5. Dynamic monitoring of mobile telecommunication towers exposed to natural loading with a FBG biaxial accelerometer

    OpenAIRE

    Antunes, P.; Travanca, R.; Varum, H.; Andre?, P.

    2011-01-01

    In this work the dynamic monitoring of a self supported telecommunications tower is presented. The feasibility of an optical FBG biaxial accelerometer to obtain the structure natural frequencies is demonstrated, recurring only to natural loading.

  6. Tuning the electronic structures of silicene and germanene by biaxial strain and electric field

    OpenAIRE

    Yan, Jia-an; Gao, Shang-peng; Stein, Ryan; Coard, Gregory

    2015-01-01

    We present a first-principles study of effects of small biaxial strain ($|\\varepsilon|\\le 5\\%$) and perpendicular electric field (E-field) on the electronic and phonon properties of low-buckled silicene and germanene. With an increase of the biaxial strain, the conduction bands at the high symmetric $\\Gamma$ and $M$ points of the first Brillouin zone shift significantly towards the Fermi level in both silicene and germanene. In contrast, the E-field changes the band dispersi...

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

    International Nuclear Information System (INIS)

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

  8. Stick-slip behavior of Indian gabbro as studied using a NIED large-scale biaxial friction apparatus

    Science.gov (United States)

    Togo, Tetsuhiro; Shimamoto, Toshihiko; Yamashita, Futoshi; Fukuyama, Eiichi; Mizoguchi, Kazuo; Urata, Yumi

    2015-04-01

    This paper reports stick-slip behaviors of Indian gabbro as studied using a new large-scale biaxial friction apparatus, built in the National Research Institute for Earth Science and Disaster Prevention (NIED), Tsukuba, Japan. The apparatus consists of the existing shaking table as the shear-loading device up to 3,600 kN, the main frame for holding two large rectangular prismatic specimens with a sliding area of 0.75 m2 and for applying normal stresses ? n up to 1.33 MPa, and a reaction force unit holding the stationary specimen to the ground. The shaking table can produce loading rates v up to 1.0 m/s, accelerations up to 9.4 m/s2, and displacements d up to 0.44 m, using four servocontrolled actuators. We report results from eight preliminary experiments conducted with room humidity on the same gabbro specimens at v = 0.1-100 mm/s and ? n = 0.66-1.33 MPa, and with d of about 0.39 m. The peak and steady-state friction coefficients were about 0.8 and 0.6, respectively, consistent with the Byerlee friction. The axial force drop or shear stress drop during an abrupt slip is linearly proportional to the amount of displacement, and the slope of this relationship determines the stiffness of the apparatus as 1.15 × 108 N/m or 153 MPa/m for the specimens we used. This low stiffness makes fault motion very unstable and the overshooting of shear stress to a negative value was recognized in some violent stick-slip events. An abrupt slip occurred in a constant rise time of 16-18 ms despite wide variation of the stress drop, and an average velocity during an abrupt slip is linearly proportional to the stress drop. The use of a large-scale shaking table has a great potential in increasing the slip rate and total displacement in biaxial friction experiments with large specimens.

  9. Electronic and optical properties of silicene under uni-axial and bi-axial mechanical strains: A first principle study

    Science.gov (United States)

    Mohan, Brij; Kumar, Ashok; Ahluwalia, P. K.

    2014-07-01

    The uni-axial and bi-axial mechanical strain mediated electronic band structures and dielectric properties of silicene have been investigated. It is found that on applying uni- and bi-axial strains, the band gap opens for smaller strain in silicene. However, on further increase of strain beyond 8% silicene changed into metal. The ultimate tensile strength estimated is 3.4 GPa. Imaginary part of dielectric function shows that the inter-band transitions are red-shifted for uni- and bi-axial tensile strains and are blue shifted for uni- and bi-axial compressive strains. Electron energy loss (EEL) function shows that the ?+? plasmon energies are red-shifted for uni- and bi-axial strains and blue-shifted for compressive strains. The ? plasmons disappears for tensile and asymmetric strains. Bi-axial asymmetric strain is found to have no influence on inter-band transitions and ?+? plasmon energies.

  10. A simplified technique for shakedown limit load determination of a large square plate with a small central hole under cyclic biaxial loading

    International Nuclear Information System (INIS)

    A simplified technique for determining the shakedown limit load of a structure was previously developed and successfully applied to benchmark shakedown problems involving uniaxial states of stress. In this paper, the simplified technique is further developed to handle cyclic biaxial loading resulting in multi-axial states of stress within the large square plate with a small central hole problem. Two material models are adopted namely: an elastic-linear strain hardening material model obeying Ziegler's linear kinematic hardening (KH) rule and an elastic-perfectly-plastic (EPP) material model. The simplified technique utilizes the finite element (FE) method and employs small displacement formulation to determine the shakedown limit load without performing lengthy time consuming full elastic-plastic cyclic loading FE simulations or conventional iterative elastic techniques. The simplified technique is utilized to generate the shakedown domain for the plate problem subjected to cyclic biaxial tension along its edges. The outcomes of the simplified technique showed very good correlation with the results of analytical solutions as well as full elastic-plastic cyclic loading FE simulations. Material hardening showed no effect on the shakedown domain of the plate in comparison to employing EPP-material.

  11. 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

  12. Practical operation of a biaxial goniometer at the wrist joint.

    Science.gov (United States)

    Buchholz, B; Wellman, H

    1997-03-01

    The objectives of this study were (a) to determine errors in wrist angle measurements from a commercially available biaxial electrogoniometer and (b) to develop a calibration routine in order to correct for these errors. Goniometric measurements were collected simultaneously with true angular data using a fixture that allowed wrist movement in one plane while restricting motion in the orthogonal plane. These data were collected in two sets of trials: flexion/extension with radial/ulnar deviation restricted, and radial/ulnar deviation with flexion/extension restricted. During these trials, we studied discrete 30 degrees increments of forearm rotation. The results showed the expected cross talk and zero drift errors during forearm rotation. The application of mathematical equations that describe the effect of goniometer twist resulted in significant error reduction for most forearm rotations. The calibration technique employs both a slope and a displacement transformation to improve the accuracy of angular data. The calibration technique may be used on data collected in the field if forearm rotation is measured simultaneously with the goniometer data. PMID:9302884

  13. Use of sigma1 criterion for evaluating long-term strength of structural steels in a plane stress state

    International Nuclear Information System (INIS)

    Conditions are discussed for applicability of the maximum tension ?1 criterion to estimate high-temperature long-term strength of structural materials in a plane stressed state. A non-excessive estimate of long-term strength from ?1 is shown possible only under biaxial tension. It is marked that under biaxial tension tests of thin-walled tubular specimens data on uniaxial strength are obtained as a rule, under axial tension of the pipes in question. In this connection while estimating long-term strength of thin-walled pipes under biaxial tension from the ?1 value it is necessary to take into consideration the level of material cold working in an axial direction. The range of the ?1 criterion applicability to evaluate long-term strength under conditions of biaxial tension is determined for pipes subjected to cold working

  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. Phase transition and band-structure tuning in InN through uniaxial and biaxial strains

    International Nuclear Information System (INIS)

    The phase transitions and band structure of InN under uniaxial and biaxial strains are systematically investigated using first-principles calculations. The main findings are summarized as follows: (I) although graphite-like phases are observed for both types of strain, the phase transitions are drastically different: second order for uniaxial strain and first order for biaxial strain. Furthermore, the second-order transition is driven by elastic and dynamical instabilities, whereas the first-order transition is driven only by elastic instability. (II) The wurtzite bandgap is always direct and that of the graphite-like phase is always indirect. Furthermore, the wurtzite bandgap is drastically enhanced by compressive uniaxial strain but reduced by tensile uniaxial strain. However, both biaxial strains greatly reduce the bandgap and eventually the semi-metallic phases are achieved. (paper)

  16. Biaxial CdTe/CaF2 films growth on amorphous surface

    International Nuclear Information System (INIS)

    A continuous and highly biaxially textured CdTe film was grown by metal organic chemical vapor deposition on an amorphous substrate using biaxial CaF2 nanorods as a buffer layer. The interface between the CdTe film and CaF2 nanorods and the morphology of the CdTe film were studied by transmission electron microscopy (TEM) and scanning electron microscopy. Both the TEM and X-ray pole figure analysis clearly reveal that the crystalline orientation of the continuous CdTe film followed the {111} biaxial texture of the CaF2 nanorods. A high density of twin faults was observed in the CdTe film. Furthermore, the near surface texture of the CdTe thin film was investigated by reflection high-energy electron diffraction (RHEED) and RHEED surface pole figure analysis. Twinning was also observed from the RHEED surface pole figure analysis.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-06-01

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

  19. 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.

  20. Conception and Construction of Biaxial Apparatus for Identification of Axial Orthotropic Material

    International Nuclear Information System (INIS)

    Plastbloc is a new process. Its principle is to use compressed and ligatured blocks made of plastic materials. These blocks could be used to build lightweight embankments, to minimize loads on underground pipes and behind retaining walls. Because the compressing during the making of blocks is unidirectional, this material is made up of stake of layers. In this case, it has an axial orthotropy. With the purpose to study the rheological behavior of this material, a large number of simple compression tests were carried out. But the identification of all parameters is possible by realization of biaxial tests. A biaxial apparatus conceived specially for this type of material was built. Preliminary studies showed the good function of this apparatus. Then, biaxial tests were carried out and the characteristic functions were identified. (author)

  1. The asymptotic solution of particle growth in the convective undercooled melt driven by a biaxial straining flow

    Science.gov (United States)

    Chen, Ming-Wen; Liu, Xiu-Min; Yang, Zhen-Chao; Wang, Zi-Dong

    2015-02-01

    A dynamical system of particle growth in the convective undercooled melt driven by a biaxial straining flow is modeled. A uniformly valid asymptotic solution for the interface evolution in particle growth is obtained by means of the multiple variable expansion method. The analytical solution as a function of both azimuth angle and polar angle shows that the interface shape of particle growth in the biaxial straining flow is significantly deformed by the biaxial straining flow. The biaxial straining flow results in higher local growth rate near the surface where the flow comes in and leads to lower local growth rate near the surface where the flow goes out. Due to the difference in local growth rate, an initially spherical particle will evolve into a prolate barrel-like shape in the biaxial straining flow.

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

    Energy Technology Data Exchange (ETDEWEB)

    Poncelet, M.; Vincent, L. [CEA Saclay, DEN/SRMA, 91 - Gif-sur-Yvette (France); Barbier, G.; Raka, B.; Desmorat, R. [LMT Cachan, ENS Cachan/CNRS/UPMC/PRES Univ. Sud Paris, 94 - Cachan (France); Courtin, S. [AREVA NP SAS, Tour AREVA, 92 - Paris La Defense (France); Barbier, G.; Le-Roux, J.C. [EDF e R and D, Departement Materiaux et Mecanique des Composants, 77 - Moret Sur Loing Cedex, (France)

    2010-09-15

    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)

  3. Proposed Route to Thin Film Crystal Si Using Biaxially Textured Foreign Template Layers

    Energy Technology Data Exchange (ETDEWEB)

    Teplin, C. W.; Ginley, D. S.; van Hest, M.F.A.M.; Perkins, J. D.; Young, D. L.; Stradins, P.; Wang, Q.; Al-Jassim, M.; Iwaniczko, E.; Leenheer, A.; Jones, K. M.; Branz, H. M.

    2005-11-01

    We have developed a new approach to growing photovoltaic-quality crystal silicon (c-Si) films on glass. Other approaches to film c-Si focus on increasing grain size in order to reduce the deleterious effects of grain boundaries. Instead, we have developed an approach to align the silicon grains biaxially (both in and out of plane) so that 1) grain boundaries are "low-angle" and have less effect on the electronic properties of the material and 2) subsequent epitaxial thickening is simplified. They key to our approach is the use of a foreign template layer that can be grown with biaxial texture directly on glass.

  4. 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

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    The electronic structures and optical properties of Cu2ZnSnS4 (CZTS) under in-plane biaxial strain were systematically investigated using first-principles calculations based on generalized gradient approximation and hybrid functional method, respectively. It is found that the fundamental bandgap at the ? 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.

  7. The biaxial flexural strength of two pressable ceramic systems.

    Science.gov (United States)

    Cattell, M J; Knowles, J C; Clarke, R L; Lynch, E

    1999-03-01

    The biaxial flexural strength of Optimal pressable ceramics and IPS Empress pressable ceramics were tested, compared and the micro-structures and compositions explored. The materials evaluated were Optimal shaded (Opcs) and unshaded (Opcus) ceramics and IPS Empress shaded (Ems) and unshaded (Emus) ceramics. Twenty-one disc specimens per material were prepared, heat-treated and tested. The piston on three-ball test ASTM F394-78 (1991) was used to test the specimens in a universal testing machine at a crosshead speed of 0.15 mm/min. Specimens were viewed in a scanning electron microscope and X-ray diffraction used to determine the phases present. Mean strengths (MPa +/- SD) were: Ems 120.1 +/- 20.5, Emus 135.8 +/- 16.0, Opcs 139.1 +/- 14.3 and Opcus 138.0 +/- 11.5. There was no statistically significant difference between Optimal shaded, Optimal unshaded and Empress unshaded strength values (p > 0.05). Empress shaded strength values were significantly lower than the other materials tested (p Weibull analysis provided m values: Ems 6.1, Emus 10.2, Opcs 12.8 and Opcus 13.9 and 1% and 5% probabilities of failure. Secondary electron imaging revealed a dense dispersal of leucite crystals in the glassy matrix of the Optimal ceramics of an average size 5.5 +/- 9.7 micron 2 for the Optimal shaded ceramic and 6.6 +/- 13.3 micron 2 for the Optimal unshaded ceramic. Leucite crystal agglomerates were evident for the Empress shaded material and a uniform distribution of fine leucite crystals (1.9 +/- 1.8 micron 2) for the Empress unshaded ceramic. Crystal and matrix microcracking were present in most of the material microstructures, together with porosity and tabular alumina platelets in the Optimal ceramics. X-ray diffraction revealed the presence of tetragonal leucite and small amounts of cubic leucite. Optimal ceramics and Empress unshaded ceramic provided higher strength and Weibull m values compared with Empress shaded ceramic. Inherent material defects were characterised and cubic leucite was identified. PMID:10079624

  8. 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

  9. Biaxial nematic and smectic phases of parallel particles with different cross sections

    Science.gov (United States)

    Martínez-Ratón, Yuri; Varga, Szabolcs; Velasco, Enrique

    2008-09-01

    We have calculated the phase diagrams of one-component fluids made of five types of biaxial particles differing in their cross sections. The orientation of the principal particle axis is fixed in space, while the second axis is allowed to freely rotate. We have constructed a free-energy density functional based on fundamental-measure theory to study the relative stability of nematic and smectic phases with uniaxial, biaxial, and tetratic symmetries. Minimization of the density functional allows us to study the phase behavior of the biaxial particles as a function of the cross-section geometry. For low values of the aspect ratio of the particle cross section, we obtain smectic phases with tetratic symmetry, although metastable with respect to the crystal, as our Monte Carlo simulation study indicates. For large particle aspect ratios and in analogy with previous work [A. G. Vanakaras, M. A. Bates, and D. J. Photinos, Phys. Chem. Chem. Phys. 5, 3700 (2003)], we have found a four-phase point where four spinodals, corresponding to phase transitions between phases with different symmetries, meet together. The location of this point is quite sensitive to particle cross section, which suggests that optimizing the particle geometry could be a useful criterion in the design of colloidal particles that can exhibit an increased stability of the biaxial nematic phase with respect to other competing phases with spatial order.

  10. Electric Field Effects on the Electronic Properties of Biaxial Strained Silicene

    Science.gov (United States)

    Stein, Ryan; Yan, Jia-An

    2014-03-01

    A first-principles study of the electronic properties of biaxial strained silicene under various perpendicular electric fields are presented. Both compressed and tensile strains are considered. Interesting dependence of the electronic structure on the strain and the electric field will be presented. Effects of both strain and electric field on the electron-phonon coupling of silicene will also be discussed.

  11. 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.

  12. 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

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

    Science.gov (United States)

    Selby, N. S.; Crawford, M.; Tracey, L.; Reno, J. L.; Pan, W.

    2014-09-01

    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.

  14. Texture evolution of vertically aligned biaxial tungsten nanorods using RHEED surface pole figure technique

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, R [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States); Liu, Y; Gaire, C; Chen, L; Wang, G-C; Lu, T-M [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States)

    2010-08-13

    Vertically aligned biaxial tungsten nanorods with cubic A15 crystal structure were deposited by DC magnetron sputtering on native oxide covered Si(100) substrates with glancing angle flux incidence ({theta} {approx} 85{sup 0}) and a two-step substrate rotation mode at room temperature. These vertical nanorods were grown to different thicknesses (10, 25, 50 and 100 nm) and analyzed for biaxial texture evolution using a highly surface sensitive reflection high-energy electron diffraction (RHEED) pole figure technique. The initial polycrystalline film begins to show the inception of biaxial texture with a fiber background between 10 and 25 nm. Biaxial texture development is eventually completed between 50 and 100 nm thicknesses of the film. The out-of-plane crystallographic direction is [002] and the in-plane texture is selected so as to obtain maximum capture area. In a comparison with 100 nm thick inclined tungsten nanorods deposited at 85{sup 0} without substrate rotation, it is found that the selection of in-plane texture does not maintain maximum in-plane capture area. This anomalous behavior is observed when the [002] texture axis is tilted {approx} 17{sup 0} from the substrate normal in the direction towards the glancing incident flux.

  15. Spin Squeezing of Superposition of Biaxial State and two qubit Bell State

    OpenAIRE

    Ashourisheikhi, Sakineh

    2013-01-01

    In this study we investigate the spin squeezing in superposition of a Biaxial state [1,2] and Bell state. Numerical and analytical solutions for the length of mean spin, mean spin direction and spin squeezing are given. It is shown that both the mean spin direction and spin squeezing parameter are determined by the coefficients of superposition and the relative phase.

  16. Stresses in sulfuric acid anodized coatings on aluminum

    Science.gov (United States)

    Alwitt, R. S.; Xu, J.; Mcclung, R. C.

    1993-01-01

    Stresses in porous anodic alumina coatings have been measured for specimens stabilized in air at different temperatures and humidities. In ambient atmosphere the stress is tensile after anodic oxidation and is compressive after sealing. Exposure to dry atmosphere causes the stress to change to strongly tensile, up to 110 MPa. The stress increase is proportional to the loss of water from the coating. These changes are reversible with changes in humidity. Similar reversible effects occur upon moderate temperature changes. The biaxial modulus of the coating is about 100 GPa.

  17. 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.

  18. Life estimation of low-cycle fatigue of pipe elbows. Proposed criteria of low-cycle fatigue life under the multi-axial stress field

    International Nuclear Information System (INIS)

    Pipe elbows were important parts frequently used in the pipelines of nuclear power, thermal power and chemical plants, and their integrity needed to be assured under seismic loads and thermal stresses considering local wall thinning or complex stress distribution due to special configuration different from straight pipe. This article investigated in details elastic-plastic stress-strain state of pipe elbow using finite element analysis and clarified there existed high bi-axial stress field at side inner surface of pipe elbow axial cracks initiated. Bi-axial stress factor was around 0.6 for sound elbow and up to 0.95 for local wall thinning at crown. Fracture strain of 1.15 was reduced to around 0.15 for bi-axial stress factor from 0.6 to 0.9. Normalized fatigue life for bi-axial stress field (0.6 - 0.8) was largely reduced to around 15, 19 and 10% of fatigue life of uni-axial state dependent on material strength level. Proposed revised universal slopes taking account of multi-axial stress factor could explain qualitatively effects of strain range, internal pressure and ratchet strain (pre-strain) on low-cycle fatigue life of pipe elbow. (T. Tanaka)

  19. Rupture propagation speed during earthquake faulting reproduced by large-scale biaxial friction experiments

    Science.gov (United States)

    Mizoguchi, K.; Fukuyama, E.; Yamashita, F.; Takizawa, S.; Kawakata, H.

    2013-12-01

    Earthquakes are generated by unstable frictional slip along pre-existing faults. Both laboratory experiments and numerical simulations have shown that the rupture process involves an initial quasi-static phase, a subsequent accelerating phase and a main dynamic rupture phase. During the main phase, the rupture front propagates at either subshear or supershear velocity, which affects the seismic wave radiation pattern. An examination on what controls the speed is crucial for improvement of earthquake hazard mitigation. Thus We conducted stick-slip experiments on meter-scale Indian gabbro rocks to observe the rupture process of the unstable periodic slip events and to measure the rupture speed along the fault. The simulated fault plane is 1.5m in length and 0.1m in width and ground by #200-300. The fault is applied at a constant normal stress of 6.7MPa and sheared parallel to the longitudinal direction of the fault at a slip rate of 0.1mm/s and up to a displacement of 40cm. The long, narrow fault geometry leads to in-plane shear rupture (mode II). in which the rupture front propagates in the direction of slip, which mimics large strike-slip earthquake faulting. Compressional-(Vp) and shear-(Vs) wave velocities of the rock sample are calculated to be 6.92km/s and 3.62km/s, respectively, based on the elastic properties (Young's modulus, 103GPa; Poisson's ratio, 0.331; Shear modulus, 38GPa). 32 biaxial strain gauges for shear strain and 16 single-axis strain gauges for normal strain were attached along the longitudinal direction of the fault at intervals of 5cm and 10cm, respectively. The local strain data were recorded at a sampling rate of 1MHz within 16 bit resolution. Load calls attached outside the fault plane measured the whole normal and shear forces applied on the fault plane, which was recorded by the same recording system. We have confirmed that the rupture process of unstable slip events consistsing of 1) an initial quasi-static phase where the slipped area spread on the fault at velocities of less than 10 m/s, 2) an accelerating phase where the rupture propagation accelerates up to 100 m/s, and 3) a main rupture phase where the rupture propagates dynamically at elastic wave velocities. These rupture nucleation process is consistent with those reported in previous studies. However, between 2) and 3) , we sometimes observed a discontinuity of rupture propagation in space and time, which is inconsistent with [Ohnaka & Shen, 1999]. Next, we estimated the rupture velocity of the main rupture phase from spatial-temporal variation in local shear strain associated with the dynamic stress reduction induced by fault slip. While several slip events showed the subshear rupture propagation similar to regular natural earthquakes, some were faster than Vs. Such supershear rupture propagation has been studied theoretically in 1970's, and reported for large strike-slip faulting earthquakes. Except for Passelègue et al. [2013], however, few laboratory experiments on rocks have confirmed the presence and this study has reproduced supershear rupture events along meter-scale fault during stick-slip experiments. We shall discuss the relationship between the rupture propagation speed and the stress heterogeneity along the fault monitored by based on the a dense array of local strain gauges.

  20. 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)

  1. 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

  2. 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...

  3. 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.

  4. Stability of Biaxial Nematic Phase for Systems with Variable Molecular Shape Anisotropy

    CERN Document Server

    Longa, L; Longa, Lech; Wydro, Thomas

    2007-01-01

    We study the influence of fluctuations in molecular shape on the stability of the biaxial nematic phase by generalizing the mean field model of Mulder and Ruijgrok [Physica A {\\bf 113}, 145 (1982)]. We limit ourselves to the case when the molecular shape anisotropy, represented by the alignment tensor, is a random variable of an annealed type. A prototype of such behavior can be found in lyotropic systems - a mixture of potassium laurate, 1-decanol, and $D_2O$, where distribution of the micellar shape adjusts to actual equilibrium conditions. Further examples of materials with the biaxial nematic phase, where molecular shape is subject to fluctuations, are thermotropic materials composed of flexible trimeric- or tetrapod-like molecular units. Our calculations show that the Gaussian equilibrium distribution of the variables describing molecular shape (dispersion force) anisotropy gives rise to new classes of the phase diagrams, absent in the original model. Depending on properties of the shape fluctuations, th...

  5. Effect of Biaxial Strain on Electronic and Thermoelectric Properties of Mg2Si

    Science.gov (United States)

    Balout, Hilal; Boulet, Pascal; Record, Marie-Christine

    2013-12-01

    The electronic and thermoelectric properties of biaxially strained magnesium silicide Mg2Si are analyzed by means of first-principle calculations and semiclassical Boltzmann theory. Electron and hole doping are examined for different doping concentrations and temperatures. Under strain the degeneracy of the electronic orbitals near the band edges is removed, the orbital bands are warped, and the energy gap closes up. These characteristics are rationalized in the light of the electron density transfers upon strain. The electrical conductivity increases with the biaxial strain, whereas neither the Seebeck coefficient nor the power factor (PF) follow this trend. Detailed analysis of the evolution of these thermoelectric properties is given in terms of the in-plane and cross-plane components. Interestingly, the maximum value of the PF is shifted towards lower temperatures when increasingly intensive strain is applied.

  6. 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)

  7. Large-Scale Biaxial Friction Experiments with an Assistance of the NIED Shaking Table

    Science.gov (United States)

    Fukuyama, E.; Mizoguchi, K.; Yamashita, F.; Togo, T.; Kawakata, H.; Yoshimitsu, N.; Shimamoto, T.; Mikoshiba, T.; Sato, M.; Minowa, C.

    2012-12-01

    We constructed a large-scale biaxial friction apparatus using a large shaking table working at NIED (table dimension is 15m x 15m). The actuator of the shaking table becomes the engine of the constant speed loading. We used a 1.5m long rock sample overlaid on a 2m one. Their height and width are both 0.5m. Therefore, the slip area is 1.5m x 0.5m. The 2m long sample moves with the shaking table and the 1.5m sample is fixed to the basement of the shaking table. Thus, the shaking table displacement controls the dislocation between two rock samples. The shaking table can generate 0.4m displacement with a velocity ranging between 0.0125mm/s and 1m/s. We used Indian gabbro for the rock sample of the present experiments. Original flatness of the sliding surface was formed less than 0.024mm undulation using a large-scale plane grinder. Surface roughness evolved as subsequent experiments were done. Wear material was generated during each experiment, whose grain size becomes bigger as the experiments proceed. This might suggest a damage evolution on the sliding surface. In some experiments we did not remove the gouge material before sliding to examine the effect of gouge layer. Normal stress can be applied up to 1.3MPa. The stiffness of this apparatus was measured experimentally and was of the order of 0.1GN/m. We first measured the coefficient of friction at low sliding velocity (0.1~1mm/s) where the steady state was achieved after the slip of ~5mm. The coefficient of friction was about 0.75 under the normal stress between 0.13 and 1.3MPa. This is consistent with those estimated by previous works using smaller rock samples. We observed that the coefficient of friction decreased gradually with increasing slip velocity, but simultaneously the friction curves at the higher velocities are characterized by stick-slip vibration. Our main aim of the experiments is to understand the rupture propagation from slow nucleation to fast unstable rupture during the loading of two contact surfaces. We recorded many unstable slip events that nucleated inside the sliding surface but did not reach the edge of the sliding surface until the termination of slip. These slip events simulate full rupture process during earthquake, including nucleation, propagation and termination of the rupture. We monitored these rupture progress using the strain change propagation measured by 16 semiconductor strain gauges recorded at a sampling rate of 1MHz. In addition, high frequency waves emitted from AE events was continuously observed by 8 piezo-electronic transducers (PZTs) at a sampling rate of 20MHz. These sensors were attached at the edge of the slipping area. The AE event started to occur where the slip was nucleated and the slip area started to expand. Unfortunately, we could not locate all AE events during the unstable rupture, because of the overprints of signals from multiple events in the PZT records. We also monitored the amplitudes of transmitted waves across the sliding surface. The amplitudes decreased just after the stick slip and recovered gradually, suggesting that the transmitted wave amplitudes might reflect the slipped area on the interface.

  8. De Vries Behavior in Smectics near a Biaxiality Induced Smectic A - Smectic C Tricritical Point

    OpenAIRE

    Saunders, Karl

    2008-01-01

    We show that a generalized Landau theory for the smectic A and C phases exhibits a biaxiality induced AC tricritical point. Proximity to this tricritical point depends on the degree of orientational order in the system; for sufficiently large orientational order the AC transition is 3D XY-like, while for sufficiently small orientational order, it is either tricritical or 1st order. We investigate each of the three types of AC transitions near tricriticality and show that for...

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

    OpenAIRE

    Le-Roux J.C.; Desmorat R.; Courtin S.; Raka B.; Barbier G.; Vincent L.; Poncelet M.

    2010-01-01

    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 t...

  10. 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.

  11. Chaos synchronization in bi-axial magnets modeled by Bloch equation

    International Nuclear Information System (INIS)

    In this paper, we show that the bi-axial magnetic material modelled by Bloch equation admits chaotic solutions for a certain set of numerical values assigned to the system of parameters and initial conditions. Using the unidirectional linear and nonlinear feedback schemes, we demonstrate that two such systems can be synchronized together. The chaotic synchronization is discussed in the context of complete synchronization which means that the difference of the states of two relevant systems converge to zero. (author)

  12. TIME DEPENDENT BIAXIAL MECHANICAL BEHAVIOR OF THE AORTIC HEART VALVE LEAFLET

    OpenAIRE

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

    2007-01-01

    Despite continued progress in the treatment of aortic valve (AV) disease, current treatments continue to be challenged to consistently restore AV function for extended durations. Improved approaches toward AV repair and replacement rests upon our ability to more fully comprehend and simulate AV function. While the elastic behavior the AV leaflet (AVL) has been previously investigated, time dependent behaviors under physiological biaxial loading states have yet to be quantified. In the current...

  13. 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...

  14. 2D nonlocal versus 3D bifurcation studies for biaxially loaded plates

    DEFF Research Database (Denmark)

    Benallal, A.; Tvergaard, Viggo

    1998-01-01

    The main objective of this work is to analyse how a two-dimensional second gradient plasticity model is able to reproduce the three-dimensional bifurcation behaviour for a biaxially loaded flat plate. While it is found that the simple model used here is able to capture them qualitatively for the longwavelength regime, it fails in reproducing them quantitatively. and in the shortwavelength regime. Consideration of a more elaborated generalized continuum should probaly overcome these difficulties.

  15. Study of the superconducting phase in silicene under biaxial tensile strain

    OpenAIRE

    Durajski, A. P.; Szcze?s?niak, D.; Szcze?s?niak, R.

    2015-01-01

    The electron-doped silicene under the influence of the biaxial tensile strain is predicted to be the phonon-mediated superconductor. By using the Eliashberg formalism, we investigate the thermodynamic properties of the superconducting silicene in the case when the tension is $5\\%$ and the electron doping equals $3.5\\times10^{14}~{\\rm cm^{-2}}$. Under such conditions, silicene monolayer is expected to exhibit the highest superconducting transition temperature ($T_C$). In part...

  16. Tune the electronic and phonon properties of silicene and germanene through biaxial strain and electric field

    Science.gov (United States)

    Yan, Jia-An; Stein, Ryan; Coard, Gregory

    2014-03-01

    We presented a density-functional study of the effects of biaxial strain and perpendicular electric field on the electronic and phonon properties of the two-dimensional (2D) silicene and germanene sheets. The two factors can be applied along the parallel and perpendicular directions independently, and therefore increase the tunability on the electronic band structure and phonon properties in these 2D systems. Important quantities such as the Grüneisen parameters will be calculated.

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

    Scientific Electronic Library Online (English)

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

    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 thi [...] s 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

  18. Instantons and solitons in a monolayer film of ferromagnetic grains with biaxial anisotropy

    International Nuclear Information System (INIS)

    We investigate domain wall and domain structure in a monolyer film consisting of ferromagnetic grains with biaxial anisotropy, which are seen to be the static versions of instanton and soliton, respectively. The equation of motion of the magnetization vector is reduced to the (1 + 2)-dimensional sine-Gordon field equation in strong anisotropy limit and the instanton and soliton configurations are obtained analytically. Various new domain structures in the ferromagnetic film are found

  19. 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...

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

    International Nuclear Information System (INIS)

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

  1. Effect of peroxide bleaching on the biaxial flexural strength and modulus of bovine dentin

    Science.gov (United States)

    Carvalho, Adriana Oliveira; Ayres, Ana Paula Almeida; de Almeida, Letícia Cunha Amaral Gonzaga; Briso, André Luiz Fraga; Rueggeberg, Frederick Allen; Giannini, Marcelo

    2015-01-01

    Objective: This study evaluated the effects of carbamide peroxide and hydrogen peroxide on the biaxial flexural strength and flexural modulus of bovine dentin. Materials and Methods: Thirty coronal dentin disks (0.5 mm thick × 6.0 mm diameter) were prepared from bovine teeth. The disks were randomly divided into three groups (n=10): A control group (unbleached), a group bleached with 10% carbamide peroxide (8 h at 37°C), and a group bleached with 38% hydrogen peroxide (three 10 min applications at 37°C). The specimens were tested in a biaxial flexural apparatus held in a universal testing machine at 1.27 mm/min until failure occurred, and the biaxial mechanical properties were calculated. For each test parameter, the data were statistically analyzed by Fisher's PLSD test (predetermined ? = 0.05). Results: The group bleached with 38% hydrogen peroxide demonstrated significantly lower flexural strength than the unbleached control group. Hydrogen peroxide treatment resulted in a significantly lower flexural modulus compared with the control group and with carbamide peroxide bleaching. Conclusion: Exposure of dentin to hydrogen peroxide significantly reduced both the flexural strength and the flexural modulus compared with the no-treatment control, whereas exposure to carbamide peroxide did not significantly affect either parameter. PMID:26038658

  2. Positive effect of biaxial stretching on the mechanical behavior of PLA-Talc nanocomposites

    Science.gov (United States)

    Ouchiar, Saadia; Stoclet, Grégory; Cabaret, Cyrille; Gloaguen, Vincent; Lefebvre, Jean-Marc; UMET-Engineering polymer science Team; UMET / Ecomeris Collaboration; UMET / LCSN Collaboration

    2015-03-01

    Poly (Lactic acid) (PLA), a biodegradable polyester issued from renewable resources, appears as a good candidate for the replacement of petrochemical-based materials due to its good combination of physical properties. However main drawbacks of PLA are its brittle behavior and its low thermal stability. One way to outclass these lacks consists in adding nanofillers into PLA. It is also recognized that the mechanical and barrier properties can be improved by biaxial drawing process. Consequently, this study deals with the enhancing effect of biaxial stretching on mechanical properties of Talc based PLA nanocomposites. The Talc content was varied between 0 to 30 wt%. This high level of talc results in a decrease in material cost, in addition to the enhancement of various physical properties. A main result is that neat PLA, which initially exhibit a brittle behavior upon uniaxial stretching at room temperature, become ductile after being biaxially stretched under appropriate conditions. More surprising is that the same behavior is observed for the filled samples. The origin of these enhancing properties will be also discussed.

  3. Thermal fatigue loading for a type 304-L stainless steel used for pressure water reactor: investigations on the effect of a nearly perfect biaxial loading, and on the cumulative fatigue life

    International Nuclear Information System (INIS)

    Fatigue-life curves are used in order to estimate crack-initiation, and also to prevent water leakage on Pressure Water Reactor pipes. Such curves are built exclusively from push-pull tests performed under constant and uniaxial strain or stress-amplitude. However, thermal fatigue corresponds to a nearly perfect biaxial stress state and severe loading fluctuations are observed in operating conditions. In this frame, these two aspects have been successively investigated in this paper: In order to investigate on potential difference between thermal fatigue and mechanical fatigue, tests have been carried out at CEA using thermal fatigue devices. They show that for an identical level of strain-amplitude, the number of cycles required to achieve crack-initiation is significantly lower under thermal fatigue. This enhanced damage results probably from a perfect biaxial state under thermal fatigue. In this frame, application of the multiaxial Zamrik's criterion seems to be very promising. In order to investigate on cumulative damage effect in fatigue, multi-level strain controlled fatigue tests have been performed. Experimental results show that linear Miner's rule is not verified. A loading sequence effect is clearly evidenced. The double linear damage rule ('DLDR') improves significantly predictions of fatigue-life. (authors)

  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. 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.

  7. 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

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

    Science.gov (United States)

    Romano, Silvano

    2004-11-01

    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 {u, j=1,2,3} and {v, k=1,2,3} define orientations of a pair of interacting particles, and let G=P(v?u), where P(⋯) denotes the second Legendre polynomial. By now, interaction models defined by suitable linear combinations of terms G 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 ?=?[-(G+G)+(G+G)]=?[-2(G+G)+G], where ? denotes a positive quantity setting energy and temperature scales (i.e., T=kT/?). 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) 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Corona, Edmundo; Gullerud, Arne S.; Haulenbeek, Kimberly K.; Reu, Phillip L.

    2015-06-01

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

  10. In-situ Curing Strain Monitoring of a Flat Plate Residual Stress Specimen Using a Chopped Stand Mat Glass/Epoxy Composite as Test Material

    Science.gov (United States)

    Jakobsen, J.; Skordos, A.; James, S.; Correia, R. G.; Jensen, M.

    2015-04-01

    The curing stresses in a newly proposed bi-axial residual stress testing configuration are studied using a chopped strand mat glass/epoxy specimen. In-situ monitoring of the curing is conducted using dielectric and fibre Bragg grating sensors. It is confirmed that a bi-axial residual stress state can be introduced in the specimens during curing and a quantification of its magnitude is presented. An alternative decomposition method used for converting the dielectric signal into a material state variable is proposed and good agreement with models found in the literature is obtained. From the cure cycles chosen it is suggested that any stress build up in the un-vitrified state is relaxed immediately and only stress build up in the vitrified state contributes to the residual stress state in the specimen.

  11. Biaxially Textured YBa2Cu3O7-? Conductors on Rolling Assisted Biaxially Textured Substrates with Critical Current Densities of 2 3 mA/cm2

    Science.gov (United States)

    Mathis, John; Goyal, Amit; Lee, Dominic; List, Fred; Paranthaman, M.; Christen, David; Specht, Eliot; Kroeger, Donald; Martin, Patrick

    1998-11-01

    Epitaxial YBa2Cu3O7-? (YBCO) films with transport critical current densities approaching 3×106 A/cm2 (77 K, 0 T) were fabricated using laser ablation of YBCO onto rolling-assisted biaxially textured-substrates (RABiTS) using a combination of thin CeO2 and thick YSZ buffer layers. The configuration of the sample was YBCO (˜0.2 µm)/YSZ (0.7 µm)/CeO2 (0.05 µm)/Ni (125 µm). The CeO2 and YSZ buffer layers were deposited using electron-beam evaporation and sputtering, respectively. The temperature window for successful pulsed-laser deposition of YBCO onto RABiTS was found to be between 740°C and 790°C.

  12. Effect of residual stress on the nanoindentation response of (100) copper single crystal

    International Nuclear Information System (INIS)

    Experimental measurements were used to investigate the effect of residual stress on the nanoindentation of (100) copper single crystal. Equi-biaxial tensile and compressive stresses were applied to the copper single crystal using a special designed apparatus. It was found that residual stresses greatly affected peak load, curvature of the loading curve, elastically recovered depth, residual depth, indentation work, pile-up amount and contact area. The Suresh and Giannakopoulos and Lee and Kwon methods were used to calculate the residual stresses from load-depth data and morphology observation of nanoindents using atomic force microscopy. Comparison of the obtained results with stress values from strain gage showed that the residual stresses analyzed from the Suresh and Giannakopoulos model agreed well with the applied stresses. -- Highlights: ? Residual stresses greatly affected various nanoindentation parameters. ? The contact area can be accurately measured from AFM observation. ? The residual stresses analyzed from the S and G model agreed well with applied stresses.

  13. Experimental investigation on transformation, reorientation and plasticity of Ni47Ti44Nb9 SMA under biaxial thermal–mechanical loading

    Science.gov (United States)

    Chen, Xiang; Peng, Xianghe; Chen, Bin; Han, Jia; Zeng, Zhongmin; Hu, Ning

    2015-07-01

    The constitutive behavior of shape memory alloy (SMA) Ni47Ti44Nb9 specimens subjected to different thermal–mechanical loading histories was investigated experimentally. This involved the application of strain by different proportional or non-proportional paths in the biaxial ??? plane at ?60 °C (Ms + 30 °C), the interaction between stress-induced martensitic transformation, reorientation and plastic deformation, temperature-induced reverse martensitic transformation and strain recovery. The results show that the equivalent stress–strain curves, as well as the pure shear and pure tensile curves, depend strongly on the thermal–mechanical loading history. For specimens deformed previously to the same equivalent strains by different paths, the equivalent recovery strains after unloading are similar, as are the spans between the reverse transformation start and final temperatures. The activated martensite variants depend strongly on loading history. The recovery of the axial strain component and that of the shear strain component due to reverse transformation occur synchronously and develop along the shortest path in the ??? plane. The results may provide some new and useful information on the effects of transformation, plasticity and loading paths for further studies and applications of such materials.

  14. 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...

  15. Ultimate Limit of Biaxial Tensile Strain and N-Type Doping for Realizing an Efficient Low-Threshold Ge Laser

    CERN Document Server

    Sukhdeo, David S; Saraswat, Krishna C; Birendra,; Dutt,; Nam, Donguk

    2015-01-01

    We theoretically investigate how the threshold of a Ge-on-Si laser can be minimized and how the slope efficiency can be maximized in presence of both biaxial tensile strain and n-type doping. Our finding shows that there exist ultimate limits beyond which point no further benefit can be realized through increased tensile strain or n-type doping. Here were quantify these limits, showing that the optimal design for minimizing threshold involves about 3.7% biaxial tensile strain and 2x1018 cm-3 n-type doping, whereas the optimal design for maximum slope efficiency involves about 2.3% biaxial tensile strain with 1x1019 cm-3 n-type doping. Increasing the strain and/or doping beyond these limits will degrade the threshold or slope efficiency, respectively.

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

    International Nuclear Information System (INIS)

    As a link the chain of ''Study for practical use of Tank Type FBR'', ''Practical use of inelastic analysis method to FBR structural design'' is carried out as a cooperative study for three years from 1984. In a cooperative study, investigation such as high-temperature deformation behavior and high-temperature fatigue life characteristics of structure materials is one of the most important problems. So we conduct tension compresion-tortion tests with Type 304 stainless steel to evaluate biaxial fatigue life characteristics at high temperature. As the first step to investigate fatigue life characteristics of reactor vessel material subjected to cyclic thermalstress, we test under time independent fatigue condition. This report shows evaluation results of these tests. We find that biaxial fatigue lives have good relation to Brown's equivalent shear strain parameter which is biaxial fatigue evaluation parameter included crack propagation characteristics. (author)

  17. Biaxially mechanical tuning of 2-D reversible and irreversible surface topologies through simultaneous and sequential wrinkling.

    Science.gov (United States)

    Yin, Jie; Yagüe, Jose Luis; Boyce, Mary C; Gleason, Karen K

    2014-02-26

    Controlled buckling is a facile means of structuring surfaces. The resulting ordered wrinkling topologies provide surface properties and features desired for multifunctional applications. Here, we study the biaxially dynamic tuning of two-dimensional wrinkled micropatterns under cyclic mechanical stretching/releasing/restretching simultaneously or sequentially. A biaxially prestretched PDMS substrate is coated with a stiff polymer deposited by initiated chemical vapor deposition (iCVD). Applying a mechanical release/restretch cycle in two directions loaded simultaneously or sequentially to the wrinkled system results in a variety of dynamic and tunable wrinkled geometries, the evolution of which is investigated using in situ optical profilometry, numerical simulations, and theoretical modeling. Results show that restretching ordered herringbone micropatterns, created through sequential release of biaxial prestrain, leads to reversible and repeatable surface topography. The initial flat surface and the same wrinkled herringbone pattern are obtained alternatively after cyclic release/restretch processes, owing to the highly ordered structure leaving no avenue for trapping irregular topological regions during cycling as further evidenced by the uniformity of strains distributions and negligible residual strain. Conversely, restretching disordered labyrinth micropatterns created through simultaneous release shows an irreversible surface topology whether after sequential or simultaneous restretching due to creation of irregular surface topologies with regions of highly concentrated strain upon formation of the labyrinth which then lead to residual strains and trapped topologies upon cycling; furthermore, these trapped topologies depend upon the subsequent strain histories as well as the cycle. The disordered labyrinth pattern varies after each cyclic release/restretch process, presenting residual shallow patterns instead of achieving a flat state. The ability to dynamically tune the highly ordered herringbone patterning through mechanical stretching or other actuation makes these wrinkles excellent candidates for tunable multifunctional surfaces properties such as reflectivity, friction, anisotropic liquid flow or boundary layer control. PMID:24490823

  18. Engineering of the space-variant linear polarization of vortex-beams in biaxially induced crystals.

    Science.gov (United States)

    Fadeyeva, Tatyana A; Alexeyev, Constantin N; Anischenko, Pavel M; Volyar, Alexander V

    2012-04-01

    We considered the propagation of Bessel beams through the biaxially induced birefringent crystal implemented by the mechanical torsion of the uniaxial crystal around its optical axis. Analyzing the solutions to the wave equation in the form of eigenmodes, we found that the system enables us to convert the beams with a uniform distribution of the linear polarization at the beam cross section into radially, azimuthally, and spirally polarized beams. Moreover, we revealed that the above system permits us to convert the beams with the space-variant linear polarization in accordance with the rule -s?s+1, where s is the topological index of the centered polarization singularity. PMID:22505105

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

    CERN Document Server

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

    2015-01-01

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

  20. 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

  1. Non-Kramers Freezing and Unfreezing of Tunneling in the Biaxial Spin Model

    CERN Document Server

    Chudnovsky, E M

    2000-01-01

    The ground state tunnel splitting for the biaxial spin model in the magnetic field, H = -D S_{x}^2 + E S_{z}^2 - g \\mu_B S_z H_z, has been investigated using an instanton approach. We find a new type of instanton and a new quantum interference phenomenon associated with it: at a certain field, H_2 = 2SE^{1/2}(D+E)^{1/2}/(g \\mu_B), the dependence of the tunneling splitting on the field switches from oscillations to a monotonic growth. The predictions of the theory can be tested in Fe_8 molecular nanomagnets.

  2. Iridium on Biaxially Textured Oxide Templates: A Concept to Grow Single Crystals on Arbitrary Substrates

    Science.gov (United States)

    Gsell, Stefan; Schreck, Matthias; Brescia, Rosaria; Stritzker, Bernd; Arendt, Paul N.; Groves, James R.

    2008-12-01

    Ion beam assisted deposition (IBAD) allows a biaxial texturing of oxide layers on polycrystalline or amorphous substrates. Even the best layers still contain an in-plane angular spread of about 4°. We report here a method to grow Ir films on top of these oxide layers with a factor of 5 lower misorientation. It is shown that the huge texture improvement involves a massive realignment of the iridium islands and an orientation averaging process. Heteroepitaxial diamond was successfully deposited on the Ir/IBAD-MgO multilayer stacks. The described texture improvement by iridium layers provides a general concept towards single crystal growth on arbitrary substrates.

  3. Dynamics of Domain Wall in a Biaxial Ferromagnet With Spin-torque

    OpenAIRE

    Liu, Xin; Liu, Xiong-jun; Ge, Mo-lin

    2004-01-01

    The dynamics of the domain wall (DW) in a biaxial ferromagnet interacting with a spin-polarized current are described by sine-gordon (SG) equation coupled with Gilbert damping term in this paper. Within our frame-work of this model, we obtain a threshold of the current in the motion of a single DW with the perturbation theory on kink soliton solution to the corresponding ferromagnetic system, and the threshold is shown to be dependent on the Gilbert damping term. Also, the m...

  4. 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.

  5. Incremental stress-strain law for graphite under multiaxial loadings

    International Nuclear Information System (INIS)

    An incremental stress-strain law for describing the nonlinear, compressible and asymmetric behavior of graphite under tension and compression as well as complex loadings is derived based on a dry friction model in the theory of plasticity. Stress-strain relations are defined by longitudinal-lateral strain measurements for specimens under uniaxial tension-compression. Agreements with experimentally determined curves from biaxial loading experiments are shown. Agreements in finite element computations using the present model with strain measurements for diametral compression and 4-point bend tests of graphite are also obtained. (orig.)

  6. Critical points and symmetries of a free energy function for biaxial nematic liquid crystals

    Science.gov (United States)

    Chillingworth, D. R. J.

    2015-05-01

    We describe a general mean field model for the free energy function for a homogeneous medium of mutually interacting molecules, based on the formalism for a biaxial nematic liquid crystal set out by Katriel et al (1986) in an influential paper in Liquid Crystals 1 and subsequently called the KKLS formalism. The free energy is expressed as the sum of an entropy term and an interaction (Hamiltonian) term. Using the language of group representation theory we identify the order parameters as averaged components of a linear transformation, and characterize the full symmetry group of the entropy term in the liquid crystal context as a wreath product SO(3) ? Z2. The symmetry-breaking role of the Hamiltonian, pointed out by Katriel et al, is here made explicit in terms of centre manifold reduction at bifurcation from isotropy. We use tools and methods of equivariant singularity theory to reduce the bifurcation study to that of a D3-invariant function on R2, ubiquitous in liquid crystal theory, and to describe the ‘universal’ bifurcation geometry in terms of the superposition of a familiar swallowtail surface controlling uniaxial equilibria and another less familiar surface controlling biaxial equilibria. In principle this provides a template for all nematic liquid crystal phase transitions close to isotropy, although further work is needed to identify the absolute minima that are the critical points representing stable phases.

  7. 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.

  8. Design and validation of a bi-axial loading bioreactor for mechanical stimulation of engineered cartilage.

    Science.gov (United States)

    Yusoff, Norwahida; Abu Osman, Noor Azuan; Pingguan-Murphy, Belinda

    2011-07-01

    A mechanical-conditioning bioreactor has been developed to provide bi-axial loading to three-dimensional (3D) tissue constructs within a highly controlled environment. The computer-controlled bioreactor is capable of applying axial compressive and shear deformations, individually or simultaneously at various regimes of strain and frequency. The reliability and reproducibility of the system were verified through validation of the spatial and temporal accuracy of platen movement, which was maintained over the operating length of the system. In the presence of actual specimens, the system was verified to be able to deliver precise bi-axial load to the specimens, in which the deformation of every specimen was observed to be relatively homogeneous. The primary use of the bioreactor is in the culture of chondrocytes seeded within an agarose hydrogel while subjected to physiological compressive and shear deformation. The system has been designed specifically to permit the repeatable quantification and characterisation of the biosynthetic activity of cells in response to a wide range of short and long term multi-dimensional loading regimes. PMID:21356602

  9. ZnS/Zn 2SnO 4 biaxial nanowire heterostructures

    Science.gov (United States)

    Shen, Jun; Ge, Binghui; Dong, Haibo; Zhang, Ning; Luo, Shudong; Ma, Wenjun; Duan, Xiaofeng; Xie, Sishen; Zhou, Weiya

    2010-03-01

    Heterostructures of side-to-side biaxial ZnS/Zn 2SnO 4 (ZTO) nanowires have been fabricated via a simple one-step thermal evaporation process. Structural characterization by high-resolution transmission electron microscopy and electron diffraction indicates that both the face-centered cubic spinel ZTO subsection and the wurtzite ZnS subsection of the heterostructure are well crystallized with a distinct interface along the heterostructure axial direction. Based on detailed analysis of the growth process of biaxial ZnS/ZTO nanowire heterostructures, there are two dominating stages: a vapor-liquid-solid (VLS) controlled growth of ZTO sub-nanowire and a self-assembly growth of ZnS sub-nanowire onto the preformed ZTO base nanowire. A growth model of the heterostructures is proposed. The presented method would be flexible and feasible for the synthesis of other nano-heterostructures with non-oxide/oxide interface to meet the growing demands of nanoscale science and technology.

  10. 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 (0pole 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

  11. Biaxial creep deformation of Zircaloy-4 PWR fuel cladding in the alpha,(alpha + beta) and beta phase temperature ranges

    International Nuclear Information System (INIS)

    The biaxial creep behaviour of Zircaloy-4 fuel cladding has been determined at temperatures between 973 - 1073 K in the alpha phase range, in the duplex (alpha + beta) region between 1098 - 1223 K and in the beta phase range between 1323 - 1473 K. This paper presents the creep data together with empirical equations which describe the creep deformation response within each phase region. (author)

  12. Analysis of uniaxial and biaxial strain impact on the linearity of fully depleted SOI nMOSFETs

    Science.gov (United States)

    Pavanello, Marcelo Antonio; Martino, João Antonio; Simoen, Eddy; Claeys, Cor

    2007-09-01

    This work studies the impact of uniaxial, biaxial and combined uniaxial-biaxial strain on the linearity of nMOSFETs from a 65 nm fully depleted (FD) SOI technology. The total harmonic distortion (THD) and third-order harmonic distortion (HD3) will be used as figures of merit. Operation in saturation and triode regimes will be the focus. When biased in the saturation region short-channel devices have been used and biased as single-transistor amplifiers. In this case, at low voltage bias the use of any kind of strain improves the THD in comparison to standard SOI. When operating in linear region as a quasi-linear resistor longer devices were studied. For operation in linear regime the HD3 is nearly the same for all devices and no clear strain influence can be found at similar bias condition. If a target on-resistance is considered, the use of biaxially or combined unxially-biaxially strained films can provide a reduction on the required gate voltage overdrive or a reduction on the device channel width without degrading the HD3.

  13. Mechanical response of cross-ply Si3N4/BN fibrous monoliths under uniaxial and biaxial loading

    International Nuclear Information System (INIS)

    Mechanical properties of hot-pressed Si3N4/BN fibrous monoliths (FMs) were evaluated under ambient conditions in four-point and biaxial flexure modes. Effects of cell orientation, 0degree/90degree and ±45degree, on elastic modulus and fracture strength of the FMs were investigated. Fracture surfaces were examined by scanning electron microscopy

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Poncelet, M.; Barbier, G.; Raka, B.; Courtin, S.; Desmorat, R.; Le-Roux, J. C.; Vincent, L.

    2010-06-01

    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.

  16. 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 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Lin; Xu, Zhenhai; Shan, Debin, E-mail: d.b.shan@gmail.com; Guo, Bin

    2013-10-01

    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.

  18. 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.

  19. 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.

  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. Quantification of the passive and active biaxial mechanical behaviour and microstructural organization of rat thoracic ducts.

    Science.gov (United States)

    Caulk, Alexander W; Nepiyushchikh, Zhanna V; Shaw, Ryan; Dixon, J Brandon; Gleason, Rudolph L

    2015-07-01

    Mechanical loading conditions are likely to play a key role in passive and active (contractile) behaviour of lymphatic vessels. The development of a microstructurally motivated model of lymphatic tissue is necessary for quantification of mechanically mediated maladaptive remodelling in the lymphatic vasculature. Towards this end, we performed cylindrical biaxial testing of Sprague-Dawley rat thoracic ducts (n = 6) and constitutive modelling to characterize their mechanical behaviour. Spontaneous contraction was quantified at transmural pressures of 3, 6 and 9 cmH2O. Cyclic inflation in calcium-free saline was performed at fixed axial stretches between 1.30 and 1.60, while recording pressure, outer diameter and axial force. A microstructurally motivated four-fibre family constitutive model originally proposed by Holzapfel et al. (Holzapfel et al. 2000 J. Elast. 61, 1-48. (doi:10.1023/A:1010835316564)) was used to quantify the passive mechanical response, and the model of Rachev and Hayashi was used to quantify the active (contractile) mechanical response. The average error between data and theory was 8.9 ± 0.8% for passive data and 6.6 ± 2.6% and 6.8 ± 3.4% for the systolic and basal conditions, respectively, for active data. Multi-photon microscopy was performed to quantify vessel wall thickness (32.2 ± 1.60 µm) and elastin and collagen organization for three loading conditions. Elastin exhibited structural 'fibre families' oriented nearly circumferentially and axially. Sample-to-sample variation was observed in collagen fibre distributions, which were often non-axisymmetric, suggesting material asymmetry. In closure, this paper presents a microstructurally motivated model that accurately captures the biaxial active and passive mechanical behaviour in lymphatics and offers potential for future research to identify parameters contributing to mechanically mediated disease development. PMID:26040600

  2. 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.

  3. Numerical simulation of stick-slip behaviours of typical faults in biaxial compression based on a frictional-hardening and frictional-softening model

    Science.gov (United States)

    Wang, X. B.; Ma, J.; Pan, Y. S.

    2013-08-01

    Stick-slip behaviours of typical faults and interactions among faults are numerically modelled using a proposed frictional-hardening and frictional-softening elastoplastic continuum model. Forty numerical tests in biaxial compression are conducted quasi-statically or dynamically in plane strain and in small or large strain mode using FLAC-3D. Faults are modelled by square or quadrilateral elements from a viewing angle perpendicular to the maximum surface of a specimen. An incremental plastic shear strain in a stick-slip cycle is involved in the model, which is calculated at the beginning of slip and then is set to be zero upon reaching its maximum at the end of stick. Thus, the repeated stick-slip behaviour can be modelled using the same set of equations, and only the evolution of an internal frictional angle is required to be different at different stages. At the slip stage, a decrease of the angle leads to an increase of the incremental plastic shear strain, while at the following stick stage, it is updated according to the present incremental plastic shear strain. Nodal velocities change at the two stages because of the use of dynamic equations even though a rate- and state-dependent law is not introduced. Effects of loading rate, fault width and maximum incremental plastic shear strain are investigated. To obtain size-independent stress-deformation curves, a slower loading is required for a finer mesh to ensure the same propagating distance of stress wave. For two intersecting faults or an echelon fault, a few small events are observed at the stick stage because of interactions among faults, whereas only one large event is observed at the slip stage. For a specimen with a bending fault, as the angle between two fault segments is large, the asynchronic softening and hardening of fault elements lead to a small stress drop at loading ends (stable sliding) rather than a saw-tooth-like behaviour (stick-slip). To validate the proposed model, a laboratory test is modelled quasi-statically that was performed on a specimen including an inclined fault oriented an angle of 60° with the horizontal direction in biaxial compression. The physical and numerical results agree well. Numerical results show that the stick-slip period is doubled if the loading velocity is halved. Compared with the rate- and state-dependent law, the present model is simple and can be implemented in FLAC-3D, capable of modelling the effects of creep, seepage and temperature. For complex faults under complex loading conditions, the proposed model can be used to identify faults prone to sliding or those with large stress drops, and to investigate active sequences of faults and their interactions. Advantages and disadvantages of square or quadrilateral meshes are also addressed, especially on the aspect of stick-slip modelling. For a bending or a single straight fault, a long stick-slip period and a low load-carrying capacity are obtained for quadrilateral meshes, but not for square meshes.

  4. Stress Management

    Science.gov (United States)

    ... Friendly Worksites Program Requirements Fit-Friendly Resources Stress Management Banner 1 - To Stress or Not to Stress - ... Decide But We Can Help What Is Stress Management? Banner 2 - Stress Continuum Graphic Banner Live life ...

  5. 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.

  6. Structural and electronic properties of LaO ?-doped SrTiO? 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? 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? 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 SrTiO? for the purpose of oxide electronics.

  7. 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.

  8. 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.

  9. Scanning electron microscopy study of the growth mechanism of biaxially aligned magnesium oxide layers grown by unbalanced magnetron sputtering

    International Nuclear Information System (INIS)

    Magnesium oxide (MgO) thin films have been grown by unbalanced magnetron sputtering on an inclined non-aligned substrate. This technique provides a way to grow biaxially aligned MgO layers. A preferential [111] out-of-plane orientation and a strong in-plane alignment have been observed. Scanning Electron Microscopy (SEM) was used to investigate the growth mechanism of these biaxially aligned MgO layers and to examine the morphology of the layers, revealing a columnar grain structure and roof-tile surface which is limited by {001} planes. Column bundling and repeated nucleation was observed. Also, the formation of highly disrupted regions caused by local heating of the growing film has been observed. A mechanism to explain the in-plane alignment is proposed

  10. Cathodoluminescence and photoconductive characteristics of single-crystal ternary CdS/CdSe/CdS biaxial nanobelts.

    Science.gov (United States)

    Hu, Linfeng; Yan, Jian; Kim, Yong; Fei, Guangtao; Watanabe, Kentaro; Sekiguchi, Takashi; Zhang, Lide; Fang, Xiaosheng

    2015-04-01

    The cathodoluminescence and optoelectronic properties based on an individual CdS/CdSe/CdS biaxial nanobelt are revealed in the present study. Both typical CdS and CdSe emissions are detected from as-grown CdS/CdSe/CdS nanobelts. The photodetector based on this nanobelt exhibits high sensitivity and excellent cycle stability. This opens a door to rational design of germanium chalcogenide compounds with unique optical properties. PMID:25384889

  11. 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

  12. 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...

  13. 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)

  14. Optical rotatory power, biaxiality, and models of chiral tilted smectic phases.

    Science.gov (United States)

    Panov, V P; Vij, J K; Shtykov, N M; Seomun, S S; Parghi, D D; Hird, M; Goodby, J W

    2003-08-01

    Among the chiral tilted smectics, the stable existence has been confirmed in numerous investigations of SmC(*)(A), (antiferroelectric smectic-C(A)) SmC(*)(F11) (SmC(*)(gamma)), SmC(*)(F12) (antiferroelectric, AF) and SmC* phases. The structures of the ferrielectric SmC(*)(F11) and SmC(*)(F12) phases suggested by different models are essentially different although all the models use the three-layer and four-layer periodicity for them. The structures of the phases were investigated using the optical rotatory power (ORP) measurements technique. The ORP was simulated using Berreman's 4 x 4-matrix method. The compound under investigation (S)-1-methylheptyl 4-(4(')-n-undecyloxy-biphenyl-4-yl-carbonyloxy) [acronym (S)-11OF1M7] clearly provides SmC(*)(F11) and SmC(*)(F12) phases, the temperature range for the existence of these phases is about 5 degrees C each. This had not been achieved for the earlier investigated antiferroelectric liquid crystal (AFLC) samples. The results obtained confirm that the unit cell of the molecular structure of these subphases is highly biaxial. Due to the biaxiality the texture of the homeotropic cell under a polarizing microscope appears nonuniform. This requires a special approach to the measurements and a simulation of the ORP, which is discussed in detail. A technique has been designed where the transmitted intensity through a polarizing microscope is measured as a function of the angle of polarization of the incident light. From the observed output, which is a biased sine wave, the ORP is being determined. In the same scan, the wavelength of light is also being automatically altered. Comparing the simulated and measured data, we can conclude that in the SmC(*)(F12) phase the distortion angle of the directors in the Ising model is lower than 10 degrees. Using the Ising model, the pitch in SmC(*)(F11) has been determined and this is found to have a strong temperature dependence. PMID:14524988

  15. 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

  16. Job Stress

    Science.gov (United States)

    ... are also a major source of emotional stress. Stress at work Even "dream jobs" have stressful deadlines, performance expectations and other responsibilities. For some, stress is the motivator that ensures things get done. ...

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

    Science.gov (United States)

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

    2007-09-01

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

  18. Development of partial safety factors for the design of partially prestressed rectangular sections in biaxial flexure

    International Nuclear Information System (INIS)

    Partial safety factors (PSFs) used in reliability-based design are intended to account for uncertainties in load, material and mathematical modeling while ensuring that the target reliability is satisfied for the relevant class of structural components in the given load combination and limit state. This paper describes the methodology in detail for developing a set of optimal reliability-based PSFs for the design of rectangular partially prestressed concrete sections subjected to biaxial flexure. The mechanical formulation of the flexural limit state is based on the principle behind prestressed concrete design recommended by IS 1343 and SP16 and failure is defined as tensile cracking of concrete extending beyond the depth of cover. The applied moments are combined according to Wood's criteria. The optimization of the PSFs is based on reliability indices obtained from first order reliability analysis of the structural components; Monte Carlo simulations are performed in each run to determine the capacity statistics and dependence between capacity and applied loads (effected through the axial loads influencing moment capacity corresponding to cracking). Numerical examples involving flexural design of partially prestressed concrete shell elements in nuclear power plant containments under accidental pressure load combination are provided. (author)

  19. Study of the superconducting phase in silicene under biaxial tensile strain

    Science.gov (United States)

    Durajski, A. P.; Szcz??niak, D.; Szcz??niak, R.

    2014-12-01

    The electron-doped silicene under the influence of the biaxial tensile strain is predicted to be the phonon-mediated superconductor. By using the Eliashberg formalism, we investigate the thermodynamic properties of the superconducting silicene in the case when the tension is 5% and the electron doping equals 3.5×1014 cm-2. Under such conditions, silicene monolayer is expected to exhibit the highest superconducting transition temperature (TC). In particular, based on the electron-phonon spectral function and assuming a wide range of the Coulomb pseudopotential values (???) it is stated that the superconducting transition temperature decreases from 18.7 K to 11.6 K. Similar behavior is observed in the case of the zeroth temperature superconducting energy gap at the Fermi level: 2?(0)? meV. Other thermodynamic parameters differ from the predictions of the Bardeen-Cooper-Schrieffer theory. In particular, the ratio of the energy gap to the critical temperature changes in the range from 4.14 to 3.87. The ratio of the specific heat jump to the specific heat in the normal state takes the values from 2.19 to 2.05, and the ratio of the critical temperature and specific heat in the normal state to the thermodynamic critical field increases from 0.143 to 0.155. It is also determined that the maximum value of the electron effective mass equals 2.11 of the electron band mass.

  20. 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.

  1. 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.

  2. 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.

    2013-12-01

    Full Text Available 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.

  3. Caracterización mecánica de aleaciones Ti-Nb mediante ensayos de flexión biaxial

    Directory of Open Access Journals (Sweden)

    Amigó, V.

    2010-12-01

    Full Text Available Nowadays titanium and titanium alloys are increasingly being used in the industry. Particularly ?-Ti alloys that stand out for having great strength properties and low elastic modulus compared to Ti c.p. or Ti-6Al-4V. Among Ti alloys, Ti-Nb alloys with high contents of alloying elements are widely used. In this work Ti-Nb alloys have been obtained using conventional powdermetallurgy. It has been studied the evolution of properties of these alloys as a function of the percentage of niobium. It can be noted the ball on three balls test used in order to characterize the samples.

    En la actualidad, cada vez, son más importantes en la industria las aleaciones de titanio. En especial las aleaciones tipo-?, que destacan por tener buenas propiedades resistentes y bajos módulos elásticos, en comparación con el Ti c.p. o el Ti-6Al-4V. Dentro de estas aleaciones cabe destacar las Ti-Nb con altos contenidos en elementos aleantes. En este trabajo se han obtenido, mediante pulvimetalurgia convencional, una serie de aleaciones Ti-Nb, en el rango del 20-40 % de niobio. Se ha obtenido la evolución de las propiedades de dichas aleaciones en función del porcentaje de niobio, mediante la utilización del ensayo de flexión biaxial con tres apoyos (three ball test.

  4. Evaluation of biaxial flexural strength and modulus of filled and unfilled adhesive systems

    Directory of Open Access Journals (Sweden)

    Liberti, Michele Santana et al.

    2009-01-01

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

  5. Diffusive void bifurcation in stressed solid

    Science.gov (United States)

    Suo, Z.; Wang, W.

    1994-09-01

    Interconnects are susceptible to solid under residual stress, electric current, and elevated temperature. As atoms diffuse, voids nucleate, drift, and enlarge. At some point, the voids of rounded shape can collapse to narrow slits and sever the interconnects. The fatal slits are often found to be transgranular, i.e., each slit cuts across a single grain. They have raised many concerns, but the underlying mechanism has remained unclear. It is proposed that a void changes shape due to surface diffusion under the combined action of surface energy, elastic energy, and electric current. The void will be rounded if surface energy prevails, but will collapse to a slit if the elastic energy or the electric current prevails. A cylindrical void in an infinite crystal under biaxial stresses, but under no electric current, is analyzed. Four things are done, as follows: (1) A suitable thermodynamic potential is minimized and maximized to select, among a family of ellipses, equilibrium void shapes. The bifurcation diagram consists of a subcritical pitchfork and two Griffith cracks. (2) A void under biased stressed is analyzed to illustrate the effect of imperfections. (3) Exact initial bifurcation modes are determined. The critical loads for the successive modes are closely separated, indicating that the shape evolution will be sensitive to initial imperfections. (4) A variational principle for shape evolution under stress, current and surface energy is identified. Stress-induced evolution time is estimated by using this variational principle.

  6. Influence of reversible epitactical stress on the electronic properties of thin superconducting films

    International Nuclear Information System (INIS)

    In this thesis new stress techniques are applied on thin superconducting (La,Sr)2CuO4 and BaFe1.8Co0.2As2 films. At one hand piezoelectric substrates are applied, which make a biaxial stress of the thin film deposed there possible, whereby the lattice parameters of the substrate are altered by an electric field. At the other hand on the base of flexible substrates by means of a bending experiment a uniaxial lattice deformation of thin film is realized.

  7. Experimental study of the flow rules of a 316 stainless steel at high and low stresses

    International Nuclear Information System (INIS)

    Creep flow rules of 316L stainless steel are studied in tensile and axial-torsion experiments. Through tensile and biaxial proportional loadings it is shown that at low creep values of epsilonkT/DGb a single kinematical variable: the internal stress takes a part in these laws. This is confirmed in non-proportional experiments. The power law with the power of nsup(*)approx.=2 relates applied and internal stresses. At higher creep rates a second scalar internal variable must be introduced and the power law no longer applies. Limiting functions in steady creep are determined for hardening and recovery. (orig.)

  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. Application of endochronic theory in multi-dimensional stress states

    International Nuclear Information System (INIS)

    The general endochronic theory and its specific constitutive equations for different stress states are studied. The determination of the material parameters, the stability and uniqueness of solution to an endochronic model are also examined. The endochronic material parameters can not be obtained by explicit means from simple tension test data. An approximate formula for these parameters is proposed. It is used to study the transverse behavior of a rod subjected to a uniaxial stress state and the behavior of a plate subjected to an in-plane biaxial stress state under static condition. Results for applications to dynamic problems are also reported. It is found that the endochronic model with simple relaxation function can be applied successfully to certain problems, although it may exhibit undesirable behavior for other problems. The flexibility in describing various material phenomena can be improved by using more realistic relaxation function and intrinsic time definition. This theory has great potential in practical applications. (orig.)

  11. Influence of dipole-dipole correlations on the stability of the biaxial nematic phase in the model bent-core liquid crystal

    International Nuclear Information System (INIS)

    A molecular theory of biaxial nematic ordering in the system of bent-core molecules has been developed in the two-particle cluster approximation which enables one to take into account short-range polar correlations determined by both electrostatic dipole-dipole interaction and polar molecular shape. All orientational order parameters and short-range correlation functions are calculated numerically as functions of temperature in the uniaxial and in the biaxial nematic phases, and the results are compared with the ones obtained in the mean-field approximation and in the cluster approximation but without taking into consideration the dipole-dipole interaction. It is shown that short-range polar correlations and, in particular, the dipole-dipole correlations dramatically increase the temperature of the transition into the biaxial nematic phase and enhancing its stability range. The results are also very sensitive to the value of the opening angle of a model bent-core molecule. (fast track communication)

  12. Influence of dipole-dipole correlations on the stability of the biaxial nematic phase in the model bent-core liquid crystal.

    Science.gov (United States)

    Osipov, Mikhail A; Paj?k, Grzegorz

    2012-04-11

    A molecular theory of biaxial nematic ordering in the system of bent-core molecules has been developed in the two-particle cluster approximation which enables one to take into account short-range polar correlations determined by both electrostatic dipole-dipole interaction and polar molecular shape. All orientational order parameters and short-range correlation functions are calculated numerically as functions of temperature in the uniaxial and in the biaxial nematic phases, and the results are compared with the ones obtained in the mean-field approximation and in the cluster approximation but without taking into consideration the dipole-dipole interaction. It is shown that short-range polar correlations and, in particular, the dipole-dipole correlations dramatically increase the temperature of the transition into the biaxial nematic phase and enhancing its stability range. The results are also very sensitive to the value of the opening angle of a model bent-core molecule. PMID:22388661

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

    DEFF Research Database (Denmark)

    Baran, Ismet; Jakobsen, Johnny

    2015-01-01

    Abstract. Process induced residual stresses may play an important role under service loading conditions for fiber reinforced composite. They may initiate premature cracks and alter the internal stress level. Therefore, the developed numerical models have to be validated with the experimental observations. In the present work, the formation of the residual stresses/strains are captured from experimental measurements and numerical models. An epoxy/steel based sample configuration is considered which creates an in-plane biaxial stress state during curing of the resin. A hole drilling process with a diameter of 5 mm is subsequently applied to the specimen and the released strains after drilling are measured using the Digital Image Correlation (DIC) technique. The material characterization of the utilized epoxy material is obtained from the experimental tests such as differential scanning calorimetry (DSC) for the curing behavior, dynamic mechanical analysis (DMA) for the elastic modulus evolution duringthe process and a thermo-mechanical analysis (TMA) for the coefficient of thermal expansion (CTE) and curing shrinkage. A numerical process model is also developed by taking the constitutive material models, i.e. cure kinetics, elastic modulus, CTE, chemical shrinkage, etc. together with the drilling process using the finite element method. The measured and predicted in-plane residual strain states are compared for the epoxy/metal biaxial stress specimen.

  14. Measurement of biaxial mechanical properties of soft tubes and arteries using piezoelectric elements and sonometry

    International Nuclear Information System (INIS)

    Arterial elasticity has gained importance in recent decades because it has been shown to be an independent predictor of cardiovascular diseases. Several in vivo and ex vivo techniques have been developed to characterize the elastic properties of vessels. In vivo techniques tend to ignore the anisotropy of the mechanical properties in the vessel wall, and therefore fail to characterize elasticity in different directions. Ex vivo techniques have been focused on studying the mechanical properties in different axes. In this paper, we present a technique that uses piezoelectric elements to measure the elasticity of soft tubes and excised arteries in two directions while maintaining the natural structure of these vessels. This technique uses sonometry data from piezoelectric elements to measure the strain in the longitudinal and circumferential directions while the tubes/arteries are being pressurized. We conducted experiments on urethane tubes to evaluate the technique and compared the experimental results with mechanical testing done on the materials used for making the tubes. We then performed sonometry experiments on excised pig carotid arteries assuming that they are transversely isotropic materials. To evaluate the sensitivity of this technique to changes in the material properties, we changed the temperature of the saline bath in which the arteries were immersed. The calculated Young's modulus from sonometry experiments for the urethane tubes and the mechanical testihe urethane tubes and the mechanical testing values showed good agreement, deviating no more than 13.1%. The elasticity values from the excised arteries and the behavior with the temperature changed agreed with previous work done in similar arteries. Therefore, we propose this technique for nondestructive testing of the biaxial properties of soft material tubes and excised arteries in their natural physiological shape.

  15. 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

  16. Measurement of biaxial mechanical properties of soft tubes and arteries using piezoelectric elements and sonometry

    Energy Technology Data Exchange (ETDEWEB)

    Bernal, Miguel; Urban, Matthew W; Greenleaf, James F [Mayo Clinic College of Medicine, Rochester, MN (United States); Rosario, Daniel; Aquino, Wilkins, E-mail: bernalrestrepo.miguel@mayo.edu [Cornell University, Ithaca, NY (United States)

    2011-06-07

    Arterial elasticity has gained importance in recent decades because it has been shown to be an independent predictor of cardiovascular diseases. Several in vivo and ex vivo techniques have been developed to characterize the elastic properties of vessels. In vivo techniques tend to ignore the anisotropy of the mechanical properties in the vessel wall, and therefore fail to characterize elasticity in different directions. Ex vivo techniques have been focused on studying the mechanical properties in different axes. In this paper, we present a technique that uses piezoelectric elements to measure the elasticity of soft tubes and excised arteries in two directions while maintaining the natural structure of these vessels. This technique uses sonometry data from piezoelectric elements to measure the strain in the longitudinal and circumferential directions while the tubes/arteries are being pressurized. We conducted experiments on urethane tubes to evaluate the technique and compared the experimental results with mechanical testing done on the materials used for making the tubes. We then performed sonometry experiments on excised pig carotid arteries assuming that they are transversely isotropic materials. To evaluate the sensitivity of this technique to changes in the material properties, we changed the temperature of the saline bath in which the arteries were immersed. The calculated Young's modulus from sonometry experiments for the urethane tubes and the mechanical testing values showed good agreement, deviating no more than 13.1%. The elasticity values from the excised arteries and the behavior with the temperature changed agreed with previous work done in similar arteries. Therefore, we propose this technique for nondestructive testing of the biaxial properties of soft material tubes and excised arteries in their natural physiological shape.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yang, C.H. [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications (BUPT), Beijing 100876 (China); Yu, Z.Y., E-mail: yuzhongyuan30@gmail.com [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications (BUPT), Beijing 100876 (China); Liu, Y.M.; Lu, P.F. [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications (BUPT), Beijing 100876 (China); Gao, T. [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Li, M.; Manzoor, S. [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications (BUPT), Beijing 100876 (China)

    2013-10-15

    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.

  18. Biaxial texture development in aluminum nitride layers during off-axis sputter deposition

    International Nuclear Information System (INIS)

    Polycrystalline aluminum nitride (AlN) layers were deposited by pulsed-dc reactive magnetron sputtering from a variable deposition angle ? = 0°–84° in 5 mTorr pure N2 at room temperature. X-ray diffraction pole figure analyses show that layers deposited from a normal angle (? = 0°) exhibit fiber texture, with a random in-plane grain orientation and the c-axis tilted by 42° ± 2° off the substrate normal, yielding wurtzite AlN grains with the {1012} plane approximately parallel (±2°) to the substrate surface. However, as ? is increased to 45°, two preferred in-plane grain orientations emerge, with populations I and II having the c-axis tilted toward and away from the deposition flux, by 53° ± 2° and 47° ± 1° off the substrate normal, respectively. Increasing ? further to 65° and 84°, results in the development of a single population II with a 43° ± 1° tilt. This developing biaxial texture is attributed to a competitive growth mode under conditions where the adatom mobility is sufficient to cause intergrain mass transport, but insufficient for the thermodynamically favored low energy {0001} planes to align parallel to the layer surface. Consequently, AlN nuclei are initially randomly oriented and form a kinetically determined crystal habit exposing {0001} and {1120} facets. The expected direction of its highest growth rate is 49° ± 5° tilted relative to the c-axis, in good agreement with the 42°–53° measured tilt. The in-plane in-plane preferred orientation for ? > 0° is well explained by the orientation dependence in the cross section of the asymmetric pyramidal nuclei to capture directional deposition flux. The observed tilt is ideal for shear mode electromechanical coupling, which is maximized at 48°.

  19. Enhanced carrier mobility and direct tunneling probability of biaxially strained Ge1-xSnx alloys for field-effect transistors applications

    Science.gov (United States)

    Liu, Lei; Liang, Renrong; Wang, Jing; Xu, Jun

    2015-05-01

    The carrier transport and tunneling capabilities of biaxially strained Ge1-xSnx alloys with (001), (110), and (111) orientations were comprehensively investigated and compared. The electron band structures of biaxially strained Ge1-xSnx alloys were calculated by the nonlocal empirical pseudopotential method and the modified virtual crystal approximation was adopted in the calculation. The electron and hole effective masses at the band edges were extracted using a parabolic line fit. It is shown that the applied biaxial strain and the high Sn composition are both helpful for the reduction of carrier effective masses, which leads to the enhanced carrier mobility and the boosted direct band-to-band-tunneling probability. Furthermore, the strain induced valance band splitting reduces the hole interband scattering, and the splitting also results in the significantly enhanced direct tunneling rate along the out-of-plane direction compared with that along the in-plane direction. The biaxially strained (111) Ge1-xSnx alloys exhibit the smallest band gaps compared with (001) and (110) orientations, leading to the highest in-plane and out-of-plane direct tunneling probabilities. The small effective masses on (110) and (111) planes in some strained conditions also contribute to the enhanced carrier mobility and tunneling probability. Therefore, the biaxially strained (110) and (111) Ge1-xSnx alloys have the potential to outperform the corresponding (001) Ge1-xSnx devices. It is important to optimize the applied biaxial strain, the Sn composition, and the substrate orientation for the design of high performance Ge1-xSnx field-effect transistors.

  20. 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...

  1. 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.

  2. Tailoring the structural and electronic properties of graphene-like ZnS monolayer using biaxial strain

    OpenAIRE

    Behera, Harihar; Mukhopadhyay, Gautam

    2013-01-01

    Our First-principles Full-Potential Density Functional Theory (DFT) calculations show that a monolayer of ZnS (ML-ZnS), which is predicted to adopt a graphene-like planar honeycomb structure with a direct band gap, undergoes strain-induced modifications in its structure and band gap when subjected to in-plane homogeneous biaxial strain ($\\delta$). ML-ZnS gets buckled for compressive strain greater than 0.92%; the buckling parameter $\\Delta$ (= 0.00 \\AA\\, for planar ML-ZnS) l...

  3. 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

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

    OpenAIRE

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

    2010-01-01

    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...

  5. Long duration biaxial cylinder testing of balloon grade polyethylene films with emphasis on automated data acquisition and control

    Science.gov (United States)

    Martone, Michael

    1994-02-01

    Characterization of a 2-dimensional material constitutive model in the practical biaxial state for engineering utility of balloon envelope structural analysis is achievable with laboratory cylinder tests. Hoop(circumferential), and longitudinal strains are time-wise measured on axially loaded pressurized cylinders. Pre-programmed ramped loading changes as well as precise long term pressure control are achieved through cascaded PID flow control loops that are part of an integrated data acquisition and process control system. Real time data reduction and analysis allow monitoring of unattended tests that have durations of up to a month. Measured and controlled parameters and variables are discussed; data analysis techniques are reviewed.

  6. 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. Dee Snider Celebrity 0:49 March of Dimes ...

  7. 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. Dee Snider Celebrity 0:49 March of Dimes ...

  8. 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: ...

  9. Stress Testing

    Science.gov (United States)

    ... from the NHLBI on Twitter. What Is Stress Testing? Stress testing provides information about how your heart works during ... is working hard and beating fast. During stress testing, you exercise (walk or run on a treadmill ...

  10. Analysis of rock stress and rock stress measurements with application to Aespoe HRL

    International Nuclear Information System (INIS)

    The process of choosing a site for a nuclear waste repository means that many aspects have to be taken into consideration. One of these is that the repository has to be mechanically stable for a long time. The mechanical stability of the rock is very difficult to determine. One of several factors, which determine the mechanical stability, is the virgin state of stress. The thesis project consists of two parts. In the first part the state of stress at Aespoe Hard Rock Laboratory had to be defined. This was done based on earlier rock stress measurements conducted during the years 1988 to 1997. Two different measurement techniques have been used, hydraulic fracturing and overcoring. During the overcoring two types of cells have been used, CSIRO HI-cell and a cell developed by the Swedish State Power Board (SSPB). In the second part of the project, investigation of the correlation between the stress and geological structures are made using numerical modelling tools such as FLAC, UDEC and 3DEC. The rock stress measurements using the hydraulic fracturing gave orientations of the horizontal stress that coincide with earlier hydraulic fracturing measurements conducted in Scandinavia. The magnitudes of rock stresses are slightly lower than the earlier reported stress magnitudes for the Scandinavian part of the earth crust. The rock stresses obtained from the overcoring resulted in higher stresses than what was predicted by the hydraulic fracturing measurements. However, the orc fracturing measurements. However, the orientation of the maximum horizontal stresses coincides well between the two techniques. The orientation is also more or less constant with respect to increasing depth. The state of stress at Aespoe is defined by using the results from the hydraulic fracturing and the measurements conducted by SSPB-cell. The measurements from the SSPB-cell are used since these have a Poisson's ratio that corresponds well with the uniaxial tests of rock samples and since the measurements have been done at a distance from the opening where no influence from the openings can be expected. Since the magnitudes of the rock stresses differ between overcoring and hydraulic fracturing, some efforts have been made to find possible causes for this. The rock stresses when conducting overcoring gave higher values overall, which could be explained by high Poisson's ratios and a minor influence from the opening as the stress measurements might have been done in the disturbed zone. The high Poisson's ratio may depend on the stress-induced microcracks, which might be initiated during the overcoring of the cell, during the drilling of the pilot borehole, in which the cell is installed, and during biaxial testing. Statistical analysis showed that there is significant differences between the mean values of Poisson's ratio obtained from biaxial tests of cores containing the CSIRO HI-cell and the SSPB-cell. Poisson's ratio is about 0.34 for CSIRO HI-cell while the SSPB-cell gave a Poisson's ratio of 0.23. The analysis also showed that Young's modulus does not differ between the techniques. The modelling in FLAC was made to simulate the overcoring and biaxial testing. The result show that it is possible to obtain extensional strain in the core during overcoring if the major principal stress is perpendicular to the borehole axis. This may lead to microcracking occurring in the core causing high Poisson's ratio, which results in higher stresses. It can also be seen from the simulation of the biaxial testing that extensional strain is achieved even if the hollow core is not damaged during overcoring. The analyses using UDEC was made to study the effect of different properties of a discontinuity, such as the dip angle, Young's modulus, Poisson's ratio, density and the normal and shear stiffness. The analyses showed that an inclined discontinuity affects the stresses especially if sliding occurs. So, the dip angle does not solely, determine the amount of disturbance of the state of stress around a discontinuity. If slip will occur or not depends, thus, on a comb

  11. Análisis de vigas tubulares de acero estructural propensas a la falla por pandeo local sometidas a flexión biaxial / Analysis of steel hollow structural beams prone to local buckling failure subjected to biaxial bending

    Scientific Electronic Library Online (English)

    NÉSTOR L, GUERRERO; MARÍA E, MARANTE; RICARDO, PICÓN; MARGGI, ROJAS; JULIO, FLÓREZ LÓPEZ.

    2006-12-01

    Full Text Available Este trabajo presenta una formulación general para el análisis de las vigas tipo cajón de acero estructural sometidas a flexión biaxial. El modelo se ha desarrollado en el marco de la teoría del daño concentrado. En este enfoque, los modelos se basan en métodos de la mecánica del daño continuo y del [...] concepto de rótula plástica. El modelo fue implementado en un programa comercial de elementos finitos. Para calibrar el modelo, fue realizado un conjunto de ensayos experimentales en el Laboratorio de Mecánica Estructural de la Universidad Centroccidental Lisandro Alvarado. El modelo fue calibrado mediante simulaciones numéricas de estos ensayos, encontrándose una buena concordancia entre las pruebas experimentales y las simulaciones numéricas. Abstract in english This paper presents a general formulation for the analysis of steel hollow structural beams prone to local buckling subjected to biaxial bending. The model has been developed within the framework of Lumped Damage Mechanics. In this approach, the models are based on methods of Continuum Damage Mechan [...] ics and the concept of plastic hinge. The model was implemented in a commercial finite element program. In order to calibrate the model, a set of experimental tests were carried out in the Structural Mechanics Laboratory at Universidad Centroccidental Lisandro Alvarado. The model was evaluated by the numerical simulation of these tests, obtaining a good agreement between the experimental tests and the numerical simulations.

  12. Angular dependence of ultrasonic wave propagation in a stressed, orthorhombic continuum: Theory and application to the measurement of stress and texture

    International Nuclear Information System (INIS)

    A theory for ultrasonic wave propagation in a symmetry plane of a biaxially stressed, orthorhombic continuum is presented. Since many of the material parameters which appear in the analysis are unknown, in particular the third-order elastic constants of polycrystalline metals, emphasis is placed on the angular dependence of the velocities. An expansion to first order in stress-induced anisotropy and to second order in textural anisotropy reveals terms with twofold, fourfold, and sixfold symmetry. Scenarios are proposed for using various properties of this symmetry to deduce the difference in magnitude and directions of the principal stresses independent of textural anisotropy and the textural anisotropy independent of the stresses. Experimental results are presented for the cases of aluminum, 304 stainless steel, and copper

  13. NULIFE - Project CABINET. RPV Assessment under Consideration of Constraint and Warm Pre-Stress Effects

    International Nuclear Information System (INIS)

    At the moment, nuclear power plant regulators do not predominantly consider constraint and biaxial effects in their concepts for failure assessment of nuclear components. The warm pre-stressing (WPS) effect is only partly considered in some assessment procedures and codes. There is also a lack of a harmonized treatment of these effects in the safety assessment of European plants. This paper introduces the project CABINET (Constraint and Biaxial Loading Effects and their Interactions Considering Thermal Transients) which is a collaborative project under the EU's Network of Excellence NULIFE. The overall objective of CABINET is to investigate and understand constraint, biaxial loading and WPS effects in terms of a clearly defined application window, especially in the light of long term operation. The focus lies on already available experimental data and methodologies. The intention is to provide recommendations for a harmonized application of those effects in European nuclear safety assessment. The possibility to include different level of analysis depending on input data and acceptance of National Regulatory Body is also being evaluated. Although the CABINET project is not completed yet, it has been found that it is possible to rationalize the different existing codes. (author)

  14. Application of the virtual crack closure technique to calculate stress intensity factors for through cracks with an oblique elliptical crack front:

    OpenAIRE

    Fawaz, S.

    1996-01-01

    Fractographic observations on fatigue tested 2024 T3 clad aluminium riveted lap-splice joints indicate oblique fronts after the initial surface or corner crack at a rivet hole has penetrated through the sheet thichness. No stress intensity factor solutions are available for this geometry subjected to remote biaxial tension, remote bending, rivet loading, and rivet interference, which are typical for a pressurized fuselage of a transport aircraft. However, comparisons are made with solutions f...

  15. TEM analysis of biaxially textured La2Zr2O7 thin films by the Moire technique

    International Nuclear Information System (INIS)

    Chemically deposited La2Zr2O7(LZO) buffer layers on biaxially textured nickel tungsten substrates for YBa2Cu3O7-?(YBCO) coated conductor technology have been investigated by transmission electron microscopy (TEM). The biaxially textured LZO thin films were 80 nm thick and were annealed at T=900 C. The samples were then prepared in plan-view for TEM investigations. The Ni grain size is about 40 ?m, whereas the grain size of the LZO films is about 100 nm. The Moire fringe contrast magnifies the misorientation of the LZO grains with respect to the underlying Ni grain by about a factor of 10. Imaging of small rotations (?3 ) of the LZO grains with respect to the underlying nickel tungsten grains was possible. Thus, the large misfit of 7.6% between the LZO film and the nickel tungsten substrate might be additionally compensated by the tilting of the small LZO grains rather than by only introducing misfit dislocations at the substrate-film interface. (orig.)

  16. Domain walls and anchoring transitions mimicking nematic biaxiality in the oxadiazole bent-core liquid crystal C7.

    Science.gov (United States)

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

    2015-05-28

    We investigate the origin of "secondary disclinations" that were recently described as new evidence of a biaxial nematic phase in an oxadiazole bent-core thermotropic liquid crystal C7. Using 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 a uniaxial nematic phase 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 bounding plates. The domain walls can be easily removed by applying a moderate 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 alignment caused by ionic impurities forming electric double layers. The model is supported by the fact that the temperature of the tangentially tilted anchoring transition decreases as the cell thickness increases and as the concentration of ionic species (added salt) increases. We also demonstrate that the surface alignment is strongly affected by thermal degradation of the samples. This study shows that C7 exhibits only a uniaxial nematic phase and demonstrates yet another mechanism (formation of "secondary disclinations") by which a uniaxial nematic phase can mimic a biaxial nematic behaviour. PMID:25820380

  17. A three-dimensional, biaxially textured oxide nanofence composed of MgO single crystal nanobelt segments

    Science.gov (United States)

    Wee, Sung Hun; Goyal, Amit; More, Karren L.; Specht, Eliot

    2009-05-01

    A unique, three-dimensional (3D), biaxially textured, MgO, nanofence comprised of single crystal MgO nanobelt segments or links was synthesized via epitaxial growth on (100) SrTiO3 substrates. Individual single crystal MgO nanobelt segments comprising the nanofence have a square cross-section with dimensions in the range of 10-20 nm and with lengths in the range from 100 nm up to 1 µm. X-ray diffraction shows that the 3D MgO nanofence has an epitaxial relation with (100) SrTiO3 substrates with a cube-on-cube, {100}lang100rang orientation and with values of the full width at half-maximum of the (200) ?-scan and the (110) phiv-scan at 4.5° and 5.5°, respectively. Such a biaxially textured oxide nanofence with single crystal segments can be used as a 3D nanotemplated substrate for epitaxial growth of wide-ranging, 3D, electronic, magnetic and electromagnetic nanodevices.

  18. Apparent dependence of rate- and state-dependent friction parameters on loading velocity and slip displacement inferred from the large-scale biaxial friction experiment data

    Science.gov (United States)

    Urata, Y.; Yamashita, F.; Fukuyama, E.

    2013-12-01

    We estimated the constitutive parameters in the rate- and state-dependent friction law by numerical simulations, using the results of large-scale biaxial rock friction experiments. Fukuyama et al. (2012, AGU Fall meeting) constructed the large-scale rock friction experiments using the shaking table at NIED. Sliding surface dimension was 1.5 m long and 0.5 m wide. During the experiments, many stick-slip events occurred, which had the following features. (i) Stress drops and recurrence intervals of the stick-slip events increased with slip displacement within a single experiment that started after the removal of gouges on the surface. (ii) Stress drops and recurrence intervals are more or less stable through an experiment, when several preceding experiments were done without gouge removal. (iii) Steady-state stress drops become large (Yamashita et al., 2012, AGU Fall meeting) and recurrence intervals become short when the loading velocity becomes fast among several experiments. We applied a single-degree-freedom spring-slider model to the friction data. The shear stress of the block obeys the rate- and state-dependent friction law (Slip law; Ruina law). We performed fully dynamic simulations. The stiffness of the spring and the mass of the block were estimated and measured in the large-scale friction experiments, respectively. We performed many numerical simulations with various values of b and L, keeping the a value constant. Then, we estimated the values of b and L which provide stick-slip behavior consistent with the experimental results. We used the experimental data when the normal stress is 1.33 MPa and the loading velocity is either 0.1 mm/s or 1.0mm/s. Our numerical simulation results suggest that (1) to fit the observation (i), we had to increase both b and L as the slip displacement increases, and (2) to fit the observation (iii), we had to increase both b and L as the loading velocity increases. The changes in b and L values are more significantly dependent on the loading velocity than on the slip displacement. Marone & Kilgore (1993, Nature) suggested that L increases with increasing gouge layer thickness. Because gouges were produced during the large-scale friction experiments, our forward modeling result (1) can be explained due to the production of gouges. In contrast, the result of large-scale friction experiments (iii) is inconsistent with previous studies (Mair et al., 2002, JGR; Anthony & Marone, 2005, JGR), as pointed out by Yamashita et al. (2012, AGU Fall meeting). This contradiction may come from the fact that the slip surface is larger and the loading velocity is higher in the present large-scale experiments than in the previous ones. We will discuss the physical interpretations of the apparent variation of b and L as is obtained in our result (2).

  19. Microplane model for concrete subject to plane stresses

    International Nuclear Information System (INIS)

    The microplane model proves in this paper to be suitable also to the description of the multiaxial behavior of concrete, subjected either to tension or to compression, with or without shear. The microcracking, which is the most relevant caused of nonlinearity, is assumed to be localized in the thin mortar layers (cement paste and fine aggregates) which separate the coarse aggregate particles: these layers, called ''microplanes'' or ''weak planes'', are assumed to be present both at the microscopic and at the macroscopic level. Each microplane is characterized by a uniaxial constitutive relationship between the normal stress and the normal strain. The behavior of the concrete as a whole is adequately described (loading in compression, strain softening excluded; loading in tension, strain softening included; unloaded either from previous tension or from previous compression). Attention is focused on plane stress situations. Comparisons are made with many test data on the biaxial behavior of concrete. (orig./HP)

  20. Influence of cyclic prestressing or additional hardening on the fatigue life of various steels under stress or strain control

    International Nuclear Information System (INIS)

    Tests performed on various steels (A42 mild steel, 304 and 316 L stainless steels) show that a new overload cycles have a favorable effect on the fatigue life in push-pull, in stress control, but a detrimental effect in strain-control, and that biaxial non-proportional loadings (90 deg out-of-phase tension and torsion) also enhance the fatigue life in stress control but reduce it in strain control. A method to estimate the influence of cyclic overloading and non-proportional loadings yields conservative predictions of the fatigue life. (authors)

  1. Temperature series to study the biaxial texturing of La2Zr2O7 buffer layers on nickel-tungsten substrates

    International Nuclear Information System (INIS)

    La2Zr2O7(LZO) buffer layers are currently of great interest for YBa2Cu3O7-x(YBCO) coated conductor technology. The mechanism of biaxial texturing of the film was investigated by varying the annealing temperature. The LZO buffer layers were prepared by chemical solution deposition (CSD) and annealed at temperatures ranging from 600 C to 1000 C in order to study the growth, biaxial-texture and microstructure of the LZO thin films. Nanovoids of 10-50 nm were found to be a typical feature of the buffer layers. Samples were investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Diffraction contrast imaging and convergent beam electron diffraction (CBED) techniques were used to investigate the microstructure of the films in plan-view and cross-section. XRD measurements showed that LZO grain growth starts at T>800 C. The average Ni grain size of the biaxially textured nickel tungsten substrates is 40 ?m and the grain size of the LZO buffer layers is 100-200 nm. Thus, even though the films are highly biaxially textured, no epitaxial growth occurs. (orig.)

  2. Temperature series to study the biaxial texturing of La{sub 2}Zr{sub 2}O{sub 7} buffer layers on nickel-tungsten substrates

    Energy Technology Data Exchange (ETDEWEB)

    Molina, L.; Eibl, O. [Inst. of Applied Physics, Univ. of Tuebingen (Germany); Engel, S.; Holzapfel, B. [IFW Dresden (Germany)

    2007-07-01

    La{sub 2}Zr{sub 2}O{sub 7}(LZO) buffer layers are currently of great interest for YBa{sub 2}Cu{sub 3}O{sub 7-x}(YBCO) coated conductor technology. The mechanism of biaxial texturing of the film was investigated by varying the annealing temperature. The LZO buffer layers were prepared by chemical solution deposition (CSD) and annealed at temperatures ranging from 600 C to 1000 C in order to study the growth, biaxial-texture and microstructure of the LZO thin films. Nanovoids of 10-50 nm were found to be a typical feature of the buffer layers. Samples were investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Diffraction contrast imaging and convergent beam electron diffraction (CBED) techniques were used to investigate the microstructure of the films in plan-view and cross-section. XRD measurements showed that LZO grain growth starts at T>800 C. The average Ni grain size of the biaxially textured nickel tungsten substrates is 40 {mu}m and the grain size of the LZO buffer layers is 100-200 nm. Thus, even though the films are highly biaxially textured, no epitaxial growth occurs. (orig.)

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

    Science.gov (United States)

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

    2013-06-01

    The annulus fibrosus (AF) of the intervertebral disk plays a critical role in vertebral load transmission that is heavily dependent on the microscale structure and composition of the tissue. With degeneration, both structure and composition are compromised, resulting in a loss of AF mechanical function. Numerous tissue engineering strategies have addressed the issue of AF degeneration, but few have focused on recapitulation of AF microstructure and function. One approach that allows for generation of engineered AF with appropriate (+/-)30° lamellar microstructure is the use of aligned electrospun scaffolds seeded with mesenchymal stem cells (MSCs) and assembled into angle-ply laminates (APL). Previous work indicates that opposing lamellar orientation is necessary for development of near native uniaxial tensile properties. However, most native AF tensile loads are applied biaxially, as the disk is subjected to multi-axial loads and is constrained by its attachments to the vertebral bodies. Thus, the objective of this study was to evaluate the biaxial mechanical response of engineered AF bilayers, and to determine the importance of opposing lamellar structure under this loading regime. Opposing bilayers, which replicate native AF structure, showed a significantly higher modulus in both testing directions compared to parallel bilayers, and reached ?60% of native AF biaxial properties. Associated with this increase in biaxial properties, significantly less shear, and significantly higher stretch in the fiber direction, was observed. These results provide additional insight into native tissue structure-function relationships, as well as new benchmarks for engineering functional AF tissue constructs. PMID:23335319

  4. Property Development for Biaxial Drawing of Ethylene-Tetrafluoroehtylene Copolymer Films and Resultant Fractural Behavior Analyzed by in Situ X-ray Measurements.

    Science.gov (United States)

    Uehara, Hiroki; Ono, Yasunori; Kakiage, Masaki; Sakamura, Takumi; Masunaga, Hiroyasu; Yukawa, Yasumasa; Higuchi, Yoshiaki; Kamiya, Hiroki; Yamanobe, Takeshi

    2015-03-19

    The property development of the ethylene-tetrafluoroethylene copolymer (ETFE) membrane induced by simultaneous biaxial drawing was investigated. Commonly, tensile strength can be increased by drawing; conversely, tear resistance decreases. In this study, the balance between tensile strength and tear resistance for the resultant ETFE membrane was optimized achieved by a combination of lamination of low molecular weight (LMW) and high molecular weight (HMW) layers and subsequent biaxial drawing. The structural factor determining tear resistance of these biaxially drawn membranes was determined based on in situ small-angle X-ray scattering (SAXS) measurement during tensile deformation simulating tearing tests. Lozenge shaped scattering, which indicated inclined lamellae, was observed during such tensile deformation of the resultant membranes. Remarkably, this inclined lamellar structure was observed for the pure LMW membrane; however, it also appeared at the interface between LMW and HMW layers within biaxially drawn membranes. For the membrane exhibiting the highest tearing strength, the fraction of such inclined lamella increased up to the critical strain corresponding to the actual sample breaking. These results confirm that the inclined lamellar structure absorbed strain during membrane tearing. PMID:25697812

  5. 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.

  6. The effect of stress on the dielectric and tunable properties of barium stannate titanate thin films

    Science.gov (United States)

    Song, Sannian; Zhai, Jiwei; Gao, Lina; Yao, Xi

    2009-02-01

    Ba(Sn0.15Ti0.85)O3 thin films were grown on the LaNiO3 buffered LaAlO3, SrTiO3, MgO, and Al2O3 single crystal substrates, respectively. These substrates provide a systematic change in the stress while maintaining the same film microstructure. The stress in the thin film induces an obvious change in the dielectric behavior. The reduction in the ferroelectric transition temperature with increasing biaxial tensile stress is attributed to the suppression of in-plane polarization due to the small lateral grain size in the films. The in-plane tensile stress in this study reduces the unit cell along electric field in the parallel plate capacitor structure and decreases the tunability.

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

    Directory of Open Access Journals (Sweden)

    Gregory Freihofer

    2015-03-01

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

  8. STRESS MANAGEMENT

    Directory of Open Access Journals (Sweden)

    Charu Jain

    2015-02-01

    Full Text Available Everyone has the right to live their life very happily. But the question arises,“Do they really live their life happily”. The answer is “No”. Human beings are not living their life happily because of stress, tension and depression in their life. Due to stress, tension and depression, a person cannot focus on their work properly and as a result of this, their focus from the work has been diverted, results in bad performance at home and at work. In this article, my focus is on stress management and how to reduce stress. Stress management encompasses those techniques which helps the human beings to survive their life by reducing stress. Stress can come at any stage of life. Stress can’t be removed totally but it can be reduced and alter. Stress management plays a vital role in human being life.

  9. The influence of the stress state on Ksub(lc)

    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. (Auth.)

  10. 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.

  11. 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...

  12. Impact of biaxial compressive strain on the heterostructures of paraelectrics KTaO3 and SrTiO3

    Directory of Open Access Journals (Sweden)

    Yi Yang

    2015-05-01

    Full Text Available We have performed density functional theory calculations to explore the impact of biaxial compressive strain on the heterostructures of paraelectrics KTaO3 and SrTiO3. We find that the strain induces strong ferroelectric distortion in KTaO3/SrTiO3 heterostructures and it stabilizes the heterostructures in ferroelectric states.The strain influences the distribution of doped holes and leads to the localization of holes in TiO2 layer. It is very interesting that ferroelectricity and ferromagnetism simultaneously present in the strained heterostructures formed by the paraelectrics KTaO3 and SrTiO3. The reversal of ferroelectric polarization changes the interface magnetization and thus results in magnetoelectric coupling effect in the heterostructures.

  13. 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.

  14. Cold Stress

    Science.gov (United States)

    ... Thermal Exposures, and Job Stress at an Airline Catering Facility Other Government Resources OSHA: Winter Weather: Plan. ... Contact CDC-INFO Workplace Safety and Health Topics Industries & Occupations Hazards & Exposures Cold Stress Diseases & Injuries Safety & ...

  15. Managing Stress

    Medline Plus

    Full Text Available ... Advocacy State Advocacy Policies and Positions Research and Data Victories and Achievements Volunteers Join an event Ambassadors ... Managing stress 3:13 Pregnancy is a stressful time for many women. You may feel happy, sad ...

  16. Manage Stress

    Science.gov (United States)

    ... time, stress can lead to serious problems like depression, anxiety, or PTSD (post-traumatic stress disorder). If you are feeling down or hopeless, talk to a doctor about depression . If you are feeling anxious, find out how ...

  17. 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...

  18. Neuromuscular Stress.

    Science.gov (United States)

    White, Timothy P.; Kern, Marialice

    1994-01-01

    Discusses exercise-induced stress that results from motor unit recruitment, the impact of recruitment on selected systemic support systems, and some of the environmental overlays that affect the degree of physiological stress. Adaptations to sustained changes in physical activity and muscle and myotendinous injury induced by stress are examined.…

  19. Life Stress

    Science.gov (United States)

    ... follow based on your results. Choose an Assessment Stress Worry Anxiety Panic Depression Resilience Workshops Afterdeployment is Moving to a New ... the site. Topics, Assessments, and Videos Post-Traumatic Stress Physical ... About Depression Life Stress Alcohol & Drugs Families with Kids Resillience ...

  20. Effect of residual stress on the nanoindentation response of (100) copper single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Li-na, E-mail: zhulina84@yahoo.com.cn [School of Engineering and Technology, China University of Geosciences, Beijing 100083 (China); Xu, Bin-shi [National Key Lab for Remanufacturing, Academy of Armored Forces Engineering, Beijing 100072 (China); Wang, Hai-dou, E-mail: wanghaidou@yahoo.com.cn [School of Engineering and Technology, China University of Geosciences, Beijing 100083 (China); National Key Lab for Remanufacturing, Academy of Armored Forces Engineering, Beijing 100072 (China); Wang, Cheng-biao [School of Engineering and Technology, China University of Geosciences, Beijing 100083 (China)

    2012-10-15

    Experimental measurements were used to investigate the effect of residual stress on the nanoindentation of (100) copper single crystal. Equi-biaxial tensile and compressive stresses were applied to the copper single crystal using a special designed apparatus. It was found that residual stresses greatly affected peak load, curvature of the loading curve, elastically recovered depth, residual depth, indentation work, pile-up amount and contact area. The Suresh and Giannakopoulos and Lee and Kwon methods were used to calculate the residual stresses from load-depth data and morphology observation of nanoindents using atomic force microscopy. Comparison of the obtained results with stress values from strain gage showed that the residual stresses analyzed from the Suresh and Giannakopoulos model agreed well with the applied stresses. -- Highlights: Black-Right-Pointing-Pointer Residual stresses greatly affected various nanoindentation parameters. Black-Right-Pointing-Pointer The contact area can be accurately measured from AFM observation. Black-Right-Pointing-Pointer The residual stresses analyzed from the S and G model agreed well with applied stresses.

  1. 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

  2. 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.

  3. Stress Analyzer

    Science.gov (United States)

    1990-01-01

    SPATE 900 Dynamic Stress Analyzer is an acronym for Stress Pattern Analysis by Thermal Emission. It detects stress-induced temperature changes in a structure and indicates the degree of stress. Ometron, Inc.'s SPATE 9000 consists of a scan unit and a data display. The scan unit contains an infrared channel focused on the test structure to collect thermal radiation, and a visual channel used to set up the scan area and interrogate the stress display. Stress data is produced by detecting minute temperature changes, down to one-thousandth of a degree Centigrade, resulting from the application to the structure of dynamic loading. The electronic data processing system correlates the temperature changes with a reference signal to determine stress level.

  4. Influence of reversible epitactical stress on the electronic properties of thin superconducting films; Einfluss von reversibler epitaktischer Verspannung auf die elektronischen Eigenschaften supraleitender Duennschichten

    Energy Technology Data Exchange (ETDEWEB)

    Trommler, Sascha

    2014-07-22

    In this thesis new stress techniques are applied on thin superconducting (La,Sr){sub 2}CuO{sub 4} and BaFe{sub 1.8}Co{sub 0.2}As{sub 2} films. At one hand piezoelectric substrates are applied, which make a biaxial stress of the thin film deposed there possible, whereby the lattice parameters of the substrate are altered by an electric field. At the other hand on the base of flexible substrates by means of a bending experiment a uniaxial lattice deformation of thin film is realized.

  5. Stress versus strain rate characteristics of Zircaloy cladding tubes subjected to various deformation paths

    International Nuclear Information System (INIS)

    Load relaxation properties of unirradiated Zircaloy nuclear fuel claddings were measured at 648 K. Deformation paths preceding the relaxation were altered in order to study the factors affecting relaxation properties. The histories chosen were constant strain rate tensile deformation, constant load creep deformation, and biaxial followed by uniaxial creep. Stress versus time records were obtained from the relaxation runs. Stress versus strain rate curves were further derived and effects of prior strain rate, strain, transient deformation and strain hardening on relaxation properties are discussed. It was found from the experimental results that after strain hardening and transient deformation saturates, the strain rate just prior to relaxation has a major effect on the stress versus strain rate characteristics. This finding holds both for the relaxation after tension and creep. Existing models could not describe these findings

  6. In-situ observation of damage nucleation in graphite under biaxial flexural loading

    OpenAIRE

    Mostafavi, M.; Duff, J; Marrow, TJ

    2010-01-01

    Graphite is used in several designs of nuclear fission reactors (e.g. The Advanced Gas Reactors in the UK, the Pebble Bed Modular Reactor and several high temperature Generation IV designsas neutron moderator and reflectors. In these applications, its structural integrity is important for safe operation. During the reactor lifetime, irradiationinduced dimensional strains and thermal strains may cause significant stresses to develop, and irradiation damage can have a detrimental effect on mech...

  7. Effects of residual stress, weld toe notch and weld defects on fatigue of welded steel structures

    Science.gov (United States)

    Shen, Wenyu

    In studying the fatigue behavior of fillet welded railroad tank car shell structures, the effects of welding residual stress, weld toe notch, and weld defects on the fatigue of fillet welded A515 steel specimens were evaluated. Both hole-drilling and sectioning measurement techniques were used to obtain residual stress information. Pad-on-plate weld specimens were designed to simulate the tank car structure for welding residual stress measurement. Simple bead-on-plate and fillet weld specimens, which have similar welding residual stresses near the weld end toe to the pad-on-plate specimens, were designed to be as compact as possible for fatigue testing. As-welded and stress-relieved simple weld specimens were tested under pulsed tension and alternating cyclic load conditions to determine stress-life and fatigue crack propagation properties. Weld toe stress concentration effects were determined by strain gage measurement. Fracture surface features and crack initiation sites were studied by visual analysis, scanning electron microscopy, and optical microscopy. Welding residual stresses were found to be biaxial tension-compression near the weld end toe and biaxial tension-tension near the weld center toe. Longitudinal tensile residual stress was significantly relieved when the applied longitudinal tensile cyclic load was greater than 14 Ksi. Test results did not show a consistent effect of tensile residual stress on the fatigue strength under pulsed tension loads. However, tensile residual stress had a significant influence on the fatigue strength under alternating cyclic loads. The weld end toe was associated with a stress concentration factor of approximately 3 and was the most critical factor in initiating fatigue cracks. Weld defects, such as slag inclusions, lack of fusion, and porosity were found to significantly affect the fatigue strength of a welded joint when the load magnitude or mean stress was low. An equivalent crack concept, based on linear elastic fracture mechanics theory, was introduced to quantify the weld toe stress concentration effect. This concept was shown to be effective for fatigue design life prediction of welded structures.

  8. Investigations of ultra shallow junction ion implanted biaxial tensile strained silicon by means of X-Ray, Raman and photoacoustic techniques

    OpenAIRE

    Horan, Ken

    2012-01-01

    The application of strain to the active channel region of the metal-oxide-semiconductor-?eld-e?ect-transistor (MOSFET) has become a necessary practice in integrated circuit (IC) fabrication. The introduction of strain allows increased carrier mobilities, and concomitant device performance enhancements, which are independent of MOSFET scaling. Biaxial tensile strained silicon ("-Si), resulting from epitaxial growth of silicon on a Si1!xGex virtual substrate gives rise to enhanced electron ...

  9. 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 ...

  10. 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.

  11. Using NEXAFS spectroscopy to probe the Biaxial Orientation of a Pyridal[2,1,3]thiadiazole-containing Donor-Acceptor Polymer

    Science.gov (United States)

    Patel, Shrayesh; Su, Greg; Luo, Chan; Wang, Ming; Heeger, Alan; Bazan, Guillermo; Chabinyc, Michael; Kramer, Edward

    2015-03-01

    Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is a powerful tool to probe the molecular orientation of conjugated polymer thin films. Here, we report on the biaxial orientation of a high mobility donor-acceptor copolymer coated on uniaxial nanogrooved substrates. The polymer system under investigation is regioregular PCDTPT based on cyclopenta[2,1-b:3,4-b ']dithiophene (CDT) and pyridal[2,1,3]thiadiazole (PT) structural units. In partial electron yield mode, NEXAFS spectroscopy is a surface sensitive technique (~2-3 nm). This is particularly useful as we are interested in probing the orientation near the interface between the polymer and the substrate. While the carbon K-edge is commonly used for NEXAFS experiments, we can take advantage of the PT unit and use the nitrogen K-edge to probe the biaxial orientation of our films. We will present the biaxial orientation of films coated on substrates with and without uniaxial nanogrooves. The results indicate that the presence of uniaxial nanogrooves are important in obtaining films with high level of orientation. Lastly, anisotropic field-effect transistor mobility values will be presented for various coating conditions.

  12. 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.

  13. 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.

  14. Development of a biaxial test facility for structural evaluation of aircraft fuselage panels

    Energy Technology Data Exchange (ETDEWEB)

    Roach, D.; Walkington, P. [Sandia National Labs., Albuquerque, NM (United States); Rice, T. [Sunwest CAD, Tijeras, NM (United States)

    1998-03-01

    The number of commercial airframes exceeding twenty years of service continues to grow. An unavoidable by-product of aircraft use is that crack and corrosion flaws develop throughout the aircraft`s skin and substructure elements. Economic barriers to the purchase of new aircraft have created an aging aircraft fleet and placed even greater demands on efficient and safe repair methods. Composite doublers, or repair patches, provide an innovative repair technique which can enhance the way aircraft are maintained. Instead of riveting multiple steel or aluminum plates to facilitate an aircraft repair, it is now possible to bond a single Boron-Epoxy composite doubler to the damaged structure. The composite doubler repair process produces both engineering and economic benefits. The FAA`s Airworthiness Assurance Center at Sandia National Labs completed a project to introduce composite doubler repair technology to the commercial aircraft industry. This paper focuses on a specialized structural test facility which was developed to evaluate the performance of composite doublers on actual aircraft structure. The facility can subject an aircraft fuselage section to a combined load environment of pressure (hoop stress) and axial, or longitudinal, stress. The tests simulate maximum cabin pressure loads and use a computerized feedback system to maintain the proper ratio between hoop and axial loads. Through the use of this full-scale test facility it was possible to: (1) assess general composite doubler response in representative flight load scenarios, and (2) verify the design and analysis approaches as applied to an L-1011 door corner repair.

  15. Nuclear stress test

    Science.gov (United States)

    ... Persantine stress test; Thallium stress test; Stress test - nuclear; Adenosine stress test; Regadenoson stress test ... had a heart attack The results of a nuclear stress test can help your doctor: Determine how ...

  16. Managing Stress

    Medline Plus

    Full Text Available ... to help you manage stress. Dee Snider Celebrity 0:49 March of Dimes HR Em 6:19 ... Anne Geddes - Photo 1:00 Mother's Day 2014 0:30 Inducing labor: Side 2:58 Managing stress ...

  17. Managing Stress

    Medline Plus

    Full Text Available ... you! Your e-mail was sent. Save to my dashboard Sign in or Sign up to save this page. Saving Just a moment, please. You've saved this page It's been added to your dashboard . Managing stress 3:13 Pregnancy is a stressful time for ...

  18. Residual stresses

    International Nuclear Information System (INIS)

    Residual stresses are stresses which exist in a material without the influence of external powers and moments. They come into existence when the volume of a material constantly changes its form as a consequence of mechanical, thermal, and/or chemical processes and is hindered by neighbouring volumes. Bodies with residual stress are in mechanical balance. These residual stresses can be manifested by means of all mechanical interventions disturbing this balance. Acoustical, optical, radiological, and magnetical methods involving material changes caused by residual stress can also serve for determining residual stress. Residual stresses have an ambivalent character. In technical practice, they are feared and liked at the same time. They cause trouble because they can be the cause for unexpected behaviour of construction elements. They are feared since they can cause failure, in the worst case with catastrophical consequences. They are appreciated, on the other hand, because, in many cases, they can contribute to improvements of the material behaviour under certain circumstances. But they are especially liked for their giving convenient and (this is most important) mostly uncontrollable explanations. For only in very few cases we have enough knowledge and possibilities for the objective evaluation of residual stresses. (orig.)

  19. An isotropic suspension system for a biaxial accelerometer using electroplated thick metal with a HAR SU-8 mold

    International Nuclear Information System (INIS)

    In this paper, a novel approach is developed to design an isotropic suspension system using thick metal freestanding micro-structures combining bulk micro-machining with electroplating based on a HAR SU-8 mold. An omega-shape isotropic suspension system composed of circular curved beams that have free switching of imaginary boundary conditions is proposed. This novel isotropic suspension design is not affected by geometric dimensional parameters and always achieves matching stiffness along the principle axes of elasticity. Using the finite element method, the isotropic suspension system was compared with an S-shaped meandering suspension system. In order to realize the suggested isotropic suspension system, a cost-effective fabrication process using electroplating with the SU-8 mold was developed to avoid expensive equipment and materials such as deep reactive-ion etching (DRIE) or a silicon-on-insulator (SOI) wafer. The fabricated isotropic suspension system was verified by electromagnetic actuation experiments. Finally, a biaxial accelerometer with isotropic suspension system was realized and tested using a vibration generator system. The proposed isotropic suspension system and the modified surface micro-machining technique based on electroplating with an SU-8 mold can contribute towards minimizing the system size, simplifying the system configuration, reducing the system price of and facilitating mass production of various types of low-cost sensors and actuators types of low-cost sensors and actuators

  20. 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 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

  1. Development of an in-plane biaxial test for forming limit curve (FLC) characterization of metallic sheets

    International Nuclear Information System (INIS)

    The main objective of this work is to propose a new experimental device able to give for a single specimen a good prediction of rheological parameters and formability under static and dynamic conditions (for intermediate strain rates). In this paper, we focus on the characterization of sheet metal forming. The proposed device is a servo-hydraulic testing machine provided with four independent dynamic actuators allowing biaxial tensile tests on cruciform specimens. The formability is evaluated thanks to the classical forming limit diagram (FLD), and one of the difficulties of this study was the design of a dedicated specimen for which the necking phenomenon appears in its central zone. If necking is located in the central zone of the specimen, then the speed ratio between the two axes controls the strain path in this zone and a whole forming limit curve can be covered. Such a specimen is proposed through a numerical and experimental validation procedure. A rigorous procedure for the detection of numerical and experimental forming strains is also presented. Finally, an experimental forming limit curve is determined and validated for an aluminium alloy dedicated to the sheet forming processes (AA5086)

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

    International Nuclear Information System (INIS)

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

  3. 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...

  4. Imaging with referenceless distortion correction and flexible regions of interest using single-shot biaxial spatiotemporally encoded MRI.

    Science.gov (United States)

    Li, Jing; Chen, Lin; Cai, Shuhui; Cai, Congbo; Zhong, Jianhui; Chen, Zhong

    2015-01-15

    Owing to its intrinsic characteristics, spatiotemporally encoded (SPEN) imaging is less sensitive to adverse effects due to field inhomogeneity in comparison with echo planar imaging, a feature highly desired for functional, diffusion, and real-time MRI. However, the quality of images obtained with SPEN MRI is still degraded by geometric distortions when field inhomogeneity exists. In this study, a single-shot biaxial SPEN (bi-SPEN) pulse sequence is implemented, utilizing a 90° and a 180° chirp pulse incorporated with two orthogonal gradients. A referenceless geometric-distortion correction based on the single-shot bi-SPEN sequence is then proposed. The distorted image acquired with the single-shot bi-SPEN sequence is corrected by iterative super-resolved reconstruction involving the field gradients estimated from a field map, which in turn is obtained from its own super-resolved data after a phase-unwrapping procedure without additional scans. In addition, the distortion correction method is applied to improve the quality of the multiple region-of-interest images obtained with single-shot bi-SPEN sequence. PMID:25462700

  5. Quantum-classical phase transition of escape rate in biaxial spin system with an arbitrarily directed magnetic field

    CERN Document Server

    Park, C S; Yoon, D H; Park, Chang-Soo; Yoo, Sahng-Kyoon; Yoon, Dal-Ho

    1999-01-01

    We investigate the escape rate of a biaxial spin particle with an arbitrarily dierected magnetic field in the easy plane, described by Hamiltonian ${\\cal H} = -AS_z^2 - BS_x^2 -H_x S_x -H_z S_z, (A>B>0)$. We derive an effective particle potential by using the method of particle mapping. With the help of the criterion for the presence of a first-order quantum-classical transition of the escape rate we obtained various phase boundary curves depending on the anisotropy parameter $b \\equiv B/A$ and the field parameters $\\alpha_{x,z} = \\alpha_{zc}(\\alpha_{xc})$. It is found from $\\alpha_{zc}(b_c)'s$ and $ (or $\\alpha_z$) increase. The phase boundary line $\\alpha_{zc} = first- and second-oredr regions are diminished due to the transverse anisotropy. Moreover, it is observed that, in the limit $\\alpha_{xc} \\to 0$, more reduction in the first-order region. We have also computed the crossover temperatures at the phase boundary :$T_c(b_c), T_c(\\alpha_{xc}, \\alpha_{zc})$.

  6. Quantum-classical transition of the escape rate of a biaxial ferromagnetic spin with an external magnetic field

    International Nuclear Information System (INIS)

    We study the model of a biaxial single ferromagnetic spin Hamiltonian with an external magnetic field applied along the medium axis. The phase transition of the escape rate is investigated. Two different but equivalent methods are implemented. Firstly, we derive the semi-classical description of the model which yields a potential and a coordinate dependent mass. Secondly, we employ the method of spin-particle mapping which yields a similar potential to that of semi-classical description but with a constant mass. The exact instanton trajectory and its corresponding action, which have not been reported in any literature is being derived. Also, the analytical expressions for the first- and second-order crossover temperatures at the phase boundary are derived. We show that the boundary between the first-and the second-order phase transitions is greatly influenced by the magnetic field. - Highlights: • A ferromagnetic spin Hamiltonian with a magnetic field is considered. • The semi-classical theory is derived using a spin coherent state path integral. • The exact instanton trajectory is obtained via a spin-particle mapping. • We study the influence of the magnetic field on the first- and second-order transitions of the escape rate

  7. 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.

  8. 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

  9. 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...

  10. Managing Stress

    Medline Plus

    Full Text Available ... Managing stress Description | Related videos | Most played video E-mail to a friend Please fill in all fields. Please enter a valid e-mail address. Your information: Your recipient's information: Your ...

  11. Stress incontinence

    Science.gov (United States)

    ... the amount of urine left after you urinate Urinalysis to check for urinary tract infection Urinary stress ... of the urologic patient: history, physical examination, and urinalysis. In: Wein AJ, ed. Campbell-Walsh Urology. 10th ...

  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. Stress Management

    Directory of Open Access Journals (Sweden)

    Prof.Univ. Dr. Paul Marinescu

    2007-05-01

    Full Text Available In the post-modern management organizational leaders have the obligation of protecting their employees against factors that could cause damages to their potentially wealthy lives. Stress is such a factor. We shall attempt by means of the present article to draw attention on certain general aspects that should be taken into account in drafting plans for fighting against and diminishing the stress faced by the employees

  14. 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

  15. Magnetostriction measurements of high strength steel under the influence of bi-axial magnetic fields

    International Nuclear Information System (INIS)

    A detailed knowledge of a material's microscopic texture is required in order to produce a realistic model of the magnetization process under applied fields. Previous studies on the magnetostriction in high strength steels have ignored the internal anisotropies due to prior material handling. To this end, a measurement utilizing two perpendicular fields was designed to interrogate the magnetic texture and microstructure of high-strength steel rods. These magnetization and magnetostriction measurements were then fitted to an energy-based domain rotation model which had been altered to address vector fields and uniaxial anisotropies. Given the simplicity of the model it is surprising to see that it captures a number of the general trends in the Data, however the fit is generally poor. Improving upon this data set will allow us to determine general magnetic characteristics of microstructure in the steels. These measurements will be incorporated into a future Vector Preisach model allowing detailed predictions of the magnetic state after stress and field changes in multiple directions

  16. Magnetostriction measurements of high strength steel under the influence of bi-axial magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Burgy, Christopher, E-mail: Christopher.burgy@navy.mil [Naval Surface Warfare Center, Carderock Division, West Bethesda, MD 20817 (United States); Department of Electrical and Computer Engineering, The George Washington University, Washington, DC 20052 (United States); Wun-fogle, Marilyn; Restorff, J.B. [Naval Surface Warfare Center, Carderock Division, West Bethesda, MD 20817 (United States); Della Torre, Edward; ElBidweihy, Hatem [Department of Electrical and Computer Engineering, The George Washington University, Washington, DC 20052 (United States)

    2014-02-15

    A detailed knowledge of a material's microscopic texture is required in order to produce a realistic model of the magnetization process under applied fields. Previous studies on the magnetostriction in high strength steels have ignored the internal anisotropies due to prior material handling. To this end, a measurement utilizing two perpendicular fields was designed to interrogate the magnetic texture and microstructure of high-strength steel rods. These magnetization and magnetostriction measurements were then fitted to an energy-based domain rotation model which had been altered to address vector fields and uniaxial anisotropies. Given the simplicity of the model it is surprising to see that it captures a number of the general trends in the Data, however the fit is generally poor. Improving upon this data set will allow us to determine general magnetic characteristics of microstructure in the steels. These measurements will be incorporated into a future Vector Preisach model allowing detailed predictions of the magnetic state after stress and field changes in multiple directions.

  17. Magnetostriction measurements of high strength steel under the influence of bi-axial magnetic fields

    Science.gov (United States)

    Burgy, Christopher; Wun-fogle, Marilyn; Restorff, J. B.; Della Torre, Edward; ElBidweihy, Hatem

    2014-02-01

    A detailed knowledge of a material's microscopic texture is required in order to produce a realistic model of the magnetization process under applied fields. Previous studies on the magnetostriction in high strength steels have ignored the internal anisotropies due to prior material handling. To this end, a measurement utilizing two perpendicular fields was designed to interrogate the magnetic texture and microstructure of high-strength steel rods. These magnetization and magnetostriction measurements were then fitted to an energy-based domain rotation model which had been altered to address vector fields and uniaxial anisotropies. Given the simplicity of the model it is surprising to see that it captures a number of the general trends in the Data, however the fit is generally poor. Improving upon this data set will allow us to determine general magnetic characteristics of microstructure in the steels. These measurements will be incorporated into a future Vector Preisach model allowing detailed predictions of the magnetic state after stress and field changes in multiple directions.

  18. A methodology for interpretation of overcoring stress measurements in anisotropic rock

    International Nuclear Information System (INIS)

    The in situ state of stress is an important parameter for the design of a repository for final disposal of spent nuclear fuel. This report presents work conducted to improve the quality of overcoring stress measurements, focused on the interpretation of overcoring rock stress measurements when accounting for possible anisotropic behavior of the rock. The work comprised: (i) development/upgrading of a computer code for calculating stresses from overcoring strains for anisotropic materials and for a general overcoring probe configuration (up to six strain rosettes with six gauges each), (ii) development of a computer code for determining elastic constants for transversely isotropic rocks from biaxial testing, and (iii) analysis of case studies of selected overcoring measurements in both isotropic and anisotropic rocks from the Posiva and SKB sites in Finland and Sweden, respectively. The work was principally limited to transversely isotropic materials, although the stress calculation code is applicable also to orthotropic materials. The developed computer codes have been geared to work primarily with the Borre and CSIRO HI three-dimensional overcoring measurement probes. Application of the codes to selected case studies, showed that the developed tools were practical and useful for interpreting overcoring stress measurements conducted in anisotropic rock. A quantitative assessment of the effects of anisotropy may thus be obtained, which provides increased reliability in the stress data. Potential gaps in existing data and/or understanding can also be identified. (orig.)

  19. Intrinsic stress in ZrN thin films: Evaluation of grain boundary contribution from in situ wafer curvature and ex situ x-ray diffraction techniques

    Energy Technology Data Exchange (ETDEWEB)

    Koutsokeras, L. E. [Departement Physique et Mecanique des Materiaux, Institut Pprime, CNRS-Universite de Poitiers-ENSMA, UPR 3346, SP2MI, Teleport 2, Bd M et P Curie, F 86962 Chasseneuil-Futuroscope (France); Department of Materials Science and Engineering, University of Ioannina, Ioannina 45110 (Greece); Abadias, G. [Departement Physique et Mecanique des Materiaux, Institut Pprime, CNRS-Universite de Poitiers-ENSMA, UPR 3346, SP2MI, Teleport 2, Bd M et P Curie, F 86962 Chasseneuil-Futuroscope (France)

    2012-05-01

    Low-mobility materials, like transition metal nitrides, usually undergo large residual stress when sputter-deposited as thin films. While the origin of stress development has been an active area of research for high-mobility materials, atomistic processes are less understood for low-mobility systems. In the present work, the contribution of grain boundary to intrinsic stress in reactively magnetron-sputtered ZrN films is evaluated by combining in situ wafer curvature measurements, providing information on the overall biaxial stress, and ex situ x-ray diffraction, giving information on elastic strain (and related stress) inside crystallites. The thermal stress contribution was also determined from the in situ stress evolution during cooling down, after deposition was stopped. The stress data are correlated with variations in film microstructure and growth energetics, in the 0.13-0.42 Pa working pressure range investigated, and discussed based on existing stress models. At low pressure (high energetic bombardment conditions), a large compressive stress is observed due to atomic peening, which induces defects inside crystallites but also promotes incorporation of excess atoms in the grain boundary. Above 0.3-0.4 Pa, the adatom surface mobility is reduced, leading to the build-up of tensile stress resulting from attractive forces between under-dense neighbouring column boundary and possible void formation, while crystallites can still remain under compressive stress.

  20. 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

  1. 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.

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

    Science.gov (United States)

    Sarman, Sten; Laaksonen, Aatto

    2012-09-14

    We have calculated the twist viscosity and the alignment angle between the director and the stream lines in shear flow of a liquid crystal model system, which forms biaxial nematic liquid crystals, as functions of the density, from the Green-Kubo relations by equilibrium molecular dynamics simulation and by a nonequilibrium molecular dynamics algorithm, where a torque conjugate to the director angular velocity is applied to rotate the director. The model system consists of a soft ellipsoid-string fluid where the ellipsoids interact according a repulsive version of the Gay-Berne potential. Four different length-to-width-to-breadth ratios have been studied. On compression, this system forms discotic or calamitic uniaxial nematic phases depending on the dimensions of the molecules, and on further compression a biaxial nematic phase is formed. In the uniaxial nematic phase there is one twist viscosity and one alignment angle. In the biaxial nematic phase there are three twist viscosities and three alignment angles corresponding to the rotation around the various directors and the different alignments of the directors relative to the stream lines, respectively. It is found that the smallest twist viscosity arises by rotation around the director formed by the long axes, the second smallest one arises by rotation around the director formed by the normals of the broadsides, and the largest one by rotation around the remaining director. The first twist viscosity is rather independent of the density whereas the last two ones increase strongly with density. One finds that there is one stable director alignment relative to the streamlines, namely where the director formed by the long axes is almost parallel to the stream lines and where the director formed by the normals of the broadsides is almost parallel to the shear plane. The relative magnitudes of the components of the twist viscosities span a fairly wide interval so this model should be useful for parameterisation experimental data. PMID:22847339

  3. Grain growth and biaxial texture of chemically deposited La2Zr2O7 buffer layers for YBCO-coated conductors

    International Nuclear Information System (INIS)

    Chemically deposited La2Zr2O7 (LZO) thin films are crucial for coated conductor production since they transfer the texture from a highly biaxially textured nickel substrate to the YBCO superconducting layer and act as nickel diffusion barriers. The misfit of LZO with respect to Ni is 7.6%. The LZO buffer layers studied in this work were deposited on biaxially textured Ni-5at%W substrates by chemical solution deposition (CSD) using the same precursor starting solutions and were annealed at temperatures ranging from 600 to 1000 deg. C for 1 h. Samples were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) in plan-view and cross-section. By combined TEM and XRD investigations on the same samples we found a clear difference in the microstructure of the LZO thin films: (i) a nanocrystalline state for T 800 deg. C with an average grain size of up to 200 nm. Thus, the LZO grain size is much smaller than the Ni grain size and the LZO buffer layers are highly biaxially textured, but no epitaxial growth occurs. Grain growth started at 800 deg. C and nanovoid formation and growth occurred during the grain growth process. The nanovoid size was determined to be 10-20 nm and small-angle grain boundaries were observed in the LZO buffer layers. The facetting of the LZO grain boundaries play an important roleZO grain boundaries play an important role in the grain growth process, samples annealed at higher temperatures had less strongly facetted grain boundaries than at lower temperatures. On top of the LZO buffer layers YBCO thin films were deposited by PLD and CSD yielding critical current densities of >1 MA/cm2 at 77 K

  4. Grain growth and biaxial texture of chemically deposited La{sub 2}Zr{sub 2}O{sub 7} buffer layers for YBCO-coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Molina, L; Eibl, O [Institute of Applied Physics, University of Tuebingen Auf der Morgenstelle 10, D-72076, Tuebingen (Germany); Engel, S; Knoth, K; Huehne, R; Holzapfel, B [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany)], E-mail: leopoldo.Molina-luna@uni-tuebingen.de

    2008-02-01

    Chemically deposited La{sub 2}Zr{sub 2}O{sub 7} (LZO) thin films are crucial for coated conductor production since they transfer the texture from a highly biaxially textured nickel substrate to the YBCO superconducting layer and act as nickel diffusion barriers. The misfit of LZO with respect to Ni is 7.6%. The LZO buffer layers studied in this work were deposited on biaxially textured Ni-5at%W substrates by chemical solution deposition (CSD) using the same precursor starting solutions and were annealed at temperatures ranging from 600 to 1000 deg. C for 1 h. Samples were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) in plan-view and cross-section. By combined TEM and XRD investigations on the same samples we found a clear difference in the microstructure of the LZO thin films: (i) a nanocrystalline state for T < 800 deg. C with grains 5-10 nm in size (ii) and a polycrystalline state for T > 800 deg. C with an average grain size of up to 200 nm. Thus, the LZO grain size is much smaller than the Ni grain size and the LZO buffer layers are highly biaxially textured, but no epitaxial growth occurs. Grain growth started at 800 deg. C and nanovoid formation and growth occurred during the grain growth process. The nanovoid size was determined to be 10-20 nm and small-angle grain boundaries were observed in the LZO buffer layers. The facetting of the LZO grain boundaries play an important role in the grain growth process, samples annealed at higher temperatures had less strongly facetted grain boundaries than at lower temperatures. On top of the LZO buffer layers YBCO thin films were deposited by PLD and CSD yielding critical current densities of >1 MA/cm{sup 2} at 77 K.

  5. 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.

  6. 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.

  7. Escape rate of a biaxial nanospin system in a magnetic field first- and second-order transition between quantum and classical regimes

    CERN Document Server

    Park, C S; Park, D K; Yoon, D H; Park, ChangSoo; Yoo, Sahng-Kyoon; Yoon, Dal-Ho

    1999-01-01

    We investigate the escape rate of the biaxial nanospin particle with a magnetic field applied along the easy axis. The model studied here is described by the Hamiltonian ${\\cal H} = -AS_z^2 - BS_x^2 - HS_z, (A>B>0)$. By reducing this Hamiltonian to a particle one, we derive, for the first time, an effective particle potential for this model and find an analytical form of the phase boundary line between first- and second-order transitions, from which a complete phase diagram can be obtained. We also derive an analytical form of the crossover temperature as a function of the applied field at the phase boundary.

  8. 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.

  9. On the origin of stress in magnetron sputtered TiN layers

    Science.gov (United States)

    Kamminga, J.-D.; de Keijser, Th. H.; Delhez, R.; Mittemeijer, E. J.

    2000-12-01

    A recently proposed model has been used to describe the state of stress in magnetron sputtered TiN layers in which the stresses are believed to be caused by atomic peening. The state of stress in the layer is described by a combination of: (i) a hydrostatic state of stress, caused by the introduction of the misfitting atoms, and (ii) a biaxial state of stress induced by the equalization of the lateral dimensions of the substrate and the layer, dilated due to the misfitting atoms and the thermal misfit due to the cooling down of the layer/substrate assembly to room temperature. The implications of the thus obtained total state of stress on x-ray diffraction measurements have been clarified and a quantitative elaboration of the growth stress as a function of the amount and type of misfitting particles has been given. It has been deduced that the growth stresses are caused by about 1 wt % Ti atoms on nitrogen sites in the TiN lattice. By comparing x-ray diffraction results of layers of different thickness, deposited simultaneously on two different substrates, it has been concluded that the growth stress in the layers depends on the layer thickness, whereas the thermal stress is equal for all layers on a given substrate. The observed layer thickness dependence of the growth stress has been associated with a (macro)strain depth profile in the layers. The distinct diffraction line broadening observed for all layers cannot be due to smallness of crystallite size and the macrostrain-depth profiles, it is ascribed to (localized) lattice defects as dislocations and low angle grain boundaries.

  10. 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)

  11. Rayleigh-Ritz vibration analysis of rectangular Mindlin plates subjected to membrane stresses

    Science.gov (United States)

    Roufaeil, O. L.; Dawe, D. J.

    1982-11-01

    A previously developed analysis of the flexural vibration of isotropic rectangular plates is extended to include the presence of a membrane stress system. The method of analysis is the Rayleigh-Ritz method and Mindlin plate theory is used which takes into account effects which are disregarded in the classical plate theory. As in the aforementioned earlier analysis the spatial variations of the deflection and two rotations over the plate middle surface are based on the use of Timoshenko beam functions. The membrane stress system comprises biaxial direct stress plus in-plane shearing stress and is uniform throughout the plate. Numerical results are presented for a number of types of plate and of applied stress which show the manner of variation of the frequencies of vibration as the intensity of stress changes. This manner of variation is similar in form to that demonstrated elsewhere by analyses based on the use of the classical plate theory but the magnitudes of the present calculated frequencies are considerably reduced for moderately thick plates.

  12. Managing Stress

    Medline Plus

    Full Text Available ... Advocacy State Advocacy Policies and Positions Research and Data Victories and Achievements Volunteers Join an event Ambassadors ... Side 2:58 Managing stress 3:13 Bidders data linkage 24:36 Developmental milest 3:12 Meet ...

  13. Stress Analysis

    OpenAIRE

    Burcharth, Hans F.

    2012-01-01

    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)

  14. 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)

  15. A polynomial approach to determine stress in an elastic body of circular section indented by conformable contact

    Directory of Open Access Journals (Sweden)

    Hinojosa-Torres J.

    2006-01-01

    Full Text Available A polynomial of degree greater than two that describes the indenter concavity shape is proposed. From the proposed polynomial, the gradient of the displacement is derived and combined with that one determined by Timoshenko and Goodier to obtain the polynomial distribution of the pressure in the cross direction of wire. By using the polynomial pressure in the "stress function" proposed by Flamant, a set of equations serving to know the stresses state in the wire section is obtained. To extend the analysis to two opposite indenters, all contributions to total stress are considered, to knowing: the stresses being produced by each one of the indenters; the biaxial tension to balance the free area of pressure. Finally, by using all contributions to total stress and determining the principal stresses, the magnitude of maximum-shear-stress at each point of elastic body it could be obtained. In order to confront the model with the reality, by associating to each point its maximum-shear-stress respective, patterns of lines representing isostresses were obtained; such patterns were compared with a photo-elasticity image, showing a good agreement. .

  16. 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...

  17. TEM analysis of biaxially textured La{sub 2}Zr{sub 2}O{sub 7} thin films by the Moire technique

    Energy Technology Data Exchange (ETDEWEB)

    Molina, L.; Eibl, O. [Inst. of Applied Physics, Univ. of Tuebingen (Germany); Knoth, K.; Holzapfel, B. [IFW Dresden (Germany)

    2007-07-01

    Chemically deposited La{sub 2}Zr{sub 2}O{sub 7}(LZO) buffer layers on biaxially textured nickel tungsten substrates for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}(YBCO) coated conductor technology have been investigated by transmission electron microscopy (TEM). The biaxially textured LZO thin films were 80 nm thick and were annealed at T=900 C. The samples were then prepared in plan-view for TEM investigations. The Ni grain size is about 40 {mu}m, whereas the grain size of the LZO films is about 100 nm. The Moire fringe contrast magnifies the misorientation of the LZO grains with respect to the underlying Ni grain by about a factor of 10. Imaging of small rotations ({<=}3 ) of the LZO grains with respect to the underlying nickel tungsten grains was possible. Thus, the large misfit of 7.6% between the LZO film and the nickel tungsten substrate might be additionally compensated by the tilting of the small LZO grains rather than by only introducing misfit dislocations at the substrate-film interface. (orig.)

  18. 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.)

  19. Residual stress investigation of copper plate and canister EB-Welds Complementary Results

    International Nuclear Information System (INIS)

    The residual stresses in copper as induced by EB-welding were studied by specimens where the weld had two configurations: either a linear or a circumferential weld. This report contains the residual stress measurements of two plates, containing linear welds, and the full-scale copper lid specimen to which a hollow cylinder section had been joined by a circumferential EB-weld. The residual stress state of the EB-welded copper specimens was investigated by X-ray diffraction (XRD), hole drilling (HD) ring core (RC) and contour method (CM). Three specimens, canister XK010 and plates X251 and X252, were subjected to a thorough study aiming at quantitative determination of the residual stress state in and around the EB-welds using XRD for surface and HD and RC for spatial stress analysis. The CM maps one stress component over a whole cross section. The surface residual stresses measured by XRD represent the machined condition of the copper material. The XRD study showed that the stress changes towards compression close to the weld in the hollow cylinder, which indicates shrinkage in the hoop direction. According to the same analogy, the shrinkage in the axial direction is much smaller. The HD measurements showed that the stress state in the base material is bi-axial and, in terms of von Mises stress, 50 MPa for the plates and 20 MPa for the cylinder part of the canister. The stress state in the EB-welds of all specimens differs clearly from the stress state in the base material being more tensile, with higher magnitudes of von Mises stress in the plate than in the canister welds. The HD and RC results were obtained using linear elastic theory. The RC measurements showed that the maximum principal stress in the BM is close to zero near the surface and it becomes slightly tensile, 10 MPa, deeper under the surface. Welding pushed the general stress state towards tension with the maximum principal stress reaching 50 MPa, deeper than 5 mm below the surface in the weld. The distribution in Step II of the EB-weld differed from this behaviour by following the trend of the BM results. The CM presented weld longitudinal stress maps over the whole cross-section of the EB-welded plates. Tensile stresses of 50 - 70 MPa were observed in the welds and widely outside the HAZ, almost 10 times the width of the weld. (orig.)

  20. Stress and Your Health

    Science.gov (United States)

    ... ePublications > Stress and your health fact sheet ePublications Stress and your health fact sheet Print this fact sheet Stress and ... activity or other distraction. Return to top Can stress affect my health? The body responds to stress by releasing stress ...

  1. Fin stress and pitch measurement using X-ray diffraction reciprocal space maps and optical scatterometry

    Science.gov (United States)

    Diebold, A. C.; Medikonda, M.; Muthinti, G. R.; Kamineni, V. K.; Fronheiser, J.; Wormington, M.; Peterson, B.; Race, J.

    2013-04-01

    Although fin metrology presents many challenges, the single crystal nature of the fins also provides opportunities to use a combination of measurement methods to determine stress and pitch. While the diffraction of light during a scatterometry measurement is well known, X-ray diffraction from a field (array) of single crystal silicon fins can also provide important information. Since some fins have Si1-xGex alloys at the top of the fin, determination of the presence of stress relaxation is another critical aspect of fin characterization. Theoretical studies predict that the bi-axially stressed crystal structure of pseudomorphic alloy films will be altered by the fin structure. For example, one expects it will be different along the length of the fin vs the width. Reciprocal space map (RSM) characterization can provide a window in the stress state of fins as well as measure pitch walking and other structural information. In this paper, we describe the fundamentals of how RSMs can be used to characterize the pitch of an array of fins as well as the stress state. We describe how this impacts the optical properties used in scatterometry measurement.

  2. 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

  3. 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.

  4. Stress Measurement by Overcoring at Shallow Depths in a Rock Slope: the Scattering of Input Data and Results

    Science.gov (United States)

    Clément, C.; Merrien-Soukatchoff, V.; Dünner, C.; Gunzburger, Y.

    2009-08-01

    This paper describes a field experiment of stress measurement using the overcoring method performed in a rock slope, called Rochers de Valabres (located in France’s Southern Alps Region), a field laboratory site prone to rockfalls. Six measurements were conducted at shallow depths from the surface, moving deeper along a sub-horizontal borehole. The experiment was conducted in heterogeneous and anisotropic gneiss, with the overcored rock elastic properties, as evaluated by biaxial and uniaxial tests, being widely scattered. Since stress calculations are sensitive to all input data uncertainties, strain inversion was, thus, performed using an experimental device and Monte Carlo simulations. The experimental device allows the assessment of rather broad confidence intervals for both stress magnitude and orientation. The results indicate that the stress state in the surface area is quite heterogeneous and may be correlated with topography. The measurements show a nonlinear stress distribution with distance to the free surface, along with high values of principal stresses, despite the vicinity of the surface. Although influenced by local topography, orientations of the principal computed stresses are characterized by a high turnover due to local heterogeneities. The results are roughly in accordance to a 2D finite element model of the site.

  5. 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

  6. Chronic Stress and Posttraumatic Stress Disorders.

    Science.gov (United States)

    Davidson, Laura M.; Baum, Andrew

    1986-01-01

    Examined the relationship between chronic stress and symptoms of posttraumatic stress syndrome in people living within five miles of the Three Mile Island (TMI) nuclear power station. Results provided evidence of substantive links between chronic stress and development of mild symptoms of posttraumatic stress disorder. (Author/BL)

  7. 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.

  8. 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.

  9. 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...

  10. 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.

  11. 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...

  12. Flexión biaxial de las columnas esbeltas de concreto en alta resistencia y los tubos llenos de concreto bajo cargas a corto y largo plazo: II Verificación

    Directory of Open Access Journals (Sweden)

    Jose A. Rodríguez-Gutiérrez

    2014-12-01

    Full Text Available En un artículo adjunto se presenta el método analítico para calcular las respuestas, a corto y largo plazo, de las columnas esbeltas de concreto en alta resistencia (HSC y de los tubos rellenos de hormigón; con condiciones de apoyo generalizados, sometidos a cargas transversales de luz y a cargas axiales excéntricas en los extremos (causando curvatura simple o doble bajo flexión uniaxial o biaxial.Los tipos de columnas que pueden ser analizadas son: ovaladas, rectangulares, circulares, C, T, L o de cualquier sección transversal arbitraria, sólida o hueca, además, las que están hechas de tubos de acero circulares y rectangulares llenos de concreto en alta resistencia. En esta publicación se presenta la validez del método y los resultados obtenidos son comparados con otros, que han sido reportados por diferentes investigadores en la literatura técnica, con más de setenta muestras de columnas.

  13. 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.

  14. 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

  15. 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.

  16. Managing Leadership Stress

    CERN Document Server

    Bal, Vidula; McDowell-Larsen, Sharon

    2011-01-01

    Everyone experiences stress, and leaders face the additional stress brought about by the unique demands of leadership: having to make decisions with limited information, to manage conflict, to do more with less . . . and faster! The consequences of stress can include health problems and deteriorating relationships. Knowing what signs of stress to look for and having a strategy for increasing your resources will help you manage leadership stress and be more effective over a long career.Table of ContentsThe Stress of Leadership 7Why Is Leadership Stressful? 8Stress Assessment 13When Stress Is Wh

  17. 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.)

  18. Stress analyses of perforated flat plates under in-plate loadings

    International Nuclear Information System (INIS)

    Strain-gaged flat plates having one, two, three, and five closely spaced holes were tested under uniaxial and 1:1 biaxial loading conditions. The experimental results of these tests were compared with corresponding calculated values obtained using the computer program TABLES, which was developed at Battelle-Columbus Laboratories. The study was conducted (1) to obtain highly reliable experimental data that can be used in the design of penetrations in vessels having large radii of curvature, (2) to evaluate the capability of the computer program TABLES for accurately predicting the stresses in perforated flat plates, (3) to complete the initial step leading toward the planned development of a method of analysis for clusters of nozzles attached to pressure vessels, and (4) to investigate the stress states in regions of closely space holes. The comparisons of calculated and experimental stresses were in good agreement, and the method of analysis was found to be capable of accurately predicting the complex state of stress in the vicinity of the closely spaced holes

  19. An optimization process for evaluating complex stress intensity factors in cracked plates from isopachics

    International Nuclear Information System (INIS)

    The complex stress intensity factor at the tips of obliquely cracked plates subjected to a biaxial load at infinity was studied by an interferometric method. The effect of higher-order terms in the series expression of the isopachics on their size and shape was studied. Thus, the optical evaluation of the stress intensity factor at the tips of the crack was improved by theoretically determining the appropriate number of terms in the series expansion of the expression defining the isopachics. The possibility of determining the optimal number of terms presents the advantage of allowing to select experimental information from any area far from the crack tip, in a zone where the validity of the experimental method is incontestable and the results do not include significant errors. In this way the values for the respective stress intensity factors approach closer to their theoretical values. The method was examplified with the evaluation of the stress intensity factor at the tip of a transverse internal crack in a plexiglas plate submitted in simple tension. (orig.)

  20. 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)

  1. Stress and Your Heart

    Medline Plus

    Full Text Available ... Videos & Tools You Are Here: Home ? Latest Health News ? Stress and Your Heart URL of this page: http://www.nlm.nih.gov/medlineplus/videos/news/Stress_Heart_043015.html Stress and Your Heart ...

  2. Stress and Your Heart

    Science.gov (United States)

    ... gov/medlineplus/videos/news/Stress_Heart_043015.html Stress and Your Heart HealthDay News Video - April 30, ... on this page, please enable JavaScript. Play video: Stress and Your Heart For closed captioning, click the ...

  3. Stress and Migraine

    Science.gov (United States)

    ... disabling headaches . Home > Stress and Migraine Print Email Stress and Migraine ACHE Newsletter Sign up for our newsletter by entering your e-mail address below. Stress and Migraine Mia Minen, MD MPH Key Points: ...

  4. Studying the effect of a hydrostatic stress/strain reduction factor on damage mechanics of concrete materials

    Science.gov (United States)

    Taqieddin, Ziad N.; Voyiadjis, George Z.

    2013-12-01

    In the non-linear finite element analysis (NFEA) of concrete materials, continuum damage mechanics (CDM) provides a powerful framework for the derivation of constitutive models capable of describing the mechanical behavior of such materials. The internal state variables of CDM can be introduced to the elastic analysis of concrete to form elastic-damage models (no inelastic strains), or to the elastic-plastic analysis in order to form coupled/uncoupled elastic-plastic-damage models. Experimental evidence that is well documented in literature shows that the susceptibility of concrete to damage and failure is distinguished under deviatoric loading from that corresponding to hydrostatic loading. A reduction factor is usually introduced into a CDM model to reduce the susceptibility of concrete to hydrostatic stresses/strains. In this work, the effect of a hydrostatic stress/strain reduction factor on the performances of two NFEA concrete models will be studied. These two (independently published) models did not provide any results showing such effect. One of these two models is an elastic-damage model, whereas the other is an uncoupled elastic-plastic-damage model. Simulations and comparisons are carried out between the performances of the two models under uniaxial tensile and compressive loading conditions. Simulations are also provided for the uncoupled elastic-plastic-damage model under the following additional loading conditions: biaxial tension and biaxial compression, uniaxial cyclic loading, and varying ratios of triaxial compressive loadings. These simulations clearly show the effect of the reduction factor on the numerically depicted behaviors of concrete materials. To have rational comparisons, the hydrostatic stress reduction factor applied to each model is chosen to be a function of the internal state variables common to both models. Therefore, once the two models are calibrated to simulate the experimental behaviors, their corresponding reduction factors are readily available at every increment of the iterative NFEA procedures.

  5. 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…

  6. 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)

  7. 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

    2015-05-01

    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.

  8. Effect of cyclic block loading on character of deformation and strength of structural materials in plane stressed state

    International Nuclear Information System (INIS)

    The paper is concerned with choice of conditions for preliminary cyclic block loading, determination of fatigue failure resistance characteristics for various structural materials under regular and selected block loading, investigation of the preliminary cyclic loading effect on regularities of elastoplastic deformation of materials concerned in the biaxial stressed state. Under selected conditions of cyclic block loading the character of damage accumulation is close to the linear law for the materials of high-srength doped steel, and VT6 alloys of concern. These materials in the initial state and after preliminary cyclic loading are anisotropic. Axial direction is characterized by a higher plastic strain resistance for steel and tangential direction - for VT6 alloy. The generalized strain curves for the materials in question are not invariant as to the stressed state type. It is stated that the effect of preliminary unsteady cyclic loading on resistance and general regularities of material deformation in the complex stressed state is insignificant. It is observed that stress-strain properties of the materials tend to vary in the following way: plastic strain resistance of the steel lowers and that of VT6 rises, anisotropy of the materials somehow decreases. The variation in the material anisotropy may be attributed to a decrease in residual stresses resulting from preliminary cyclic loading

  9. 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.

  10. 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…

  11. Stress and eating behavior

    OpenAIRE

    Peters, Achim; Langemann, Dirk

    2010-01-01

    How stress, the stress response, and the adaptation of the stress response influence our eating behavior is a central question in brain research and medicine. In this report, we highlight recent advances showing the close links between eating behavior, the stress system, and neurometabolism.

  12. Is Aging Stressful?

    Science.gov (United States)

    Hoffman, Stephanie B.

    It is often assumed that old age is a time of numerous losses, irritants, and stress. Although researchers have examined the interrelationship of stress, health, and happiness in old age, stress is usually operationalized as a response to major life events; however, stress can also be operationalized as a response to the everyday experiences of…

  13. School stress in children

    OpenAIRE

    Mallett, S.

    1997-01-01

    Most of us can empathise with feeling stressed. Each of us has our own unique interpretation of what stress is and our own understanding of what stress feels like. We each feel stress from a variety of sources and for a variety of reasons. We all have different coping strategies, which may or may not be effective. It is likely we learned our coping strategies in childhood; children who cope successfully with stress are likely to become adults who cope with stress successfully. Stress is not n...

  14. 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 ...

  15. A parametric evaluation of residual stress resulting from abrasive waterjet surface treatments with elastic prestress: Experiments and modeling

    Science.gov (United States)

    Sadasivam, Balaji

    Recent advances in Abrasive Waterjet (AWJ) technology have resulted in a new process for surface treatment that is capable of introducing compressive residual stresses and a surface texture that facilitates bonding. The current research focuses on quantifying the influences of Abrasive Waterjet Peening (AWJP) with elastic prestress on the surface and subsurface residual stress distributions and surface texture of three engineering metals (ASTM 228, Ti6Al4V and inconel 718). A design of experiments (DOE) and an analysis of variance (ANOVA) were used to identify the treatment parameters with primary contributions to the residual stress field. The applied elastic prestress ranged from 0 to 75% of the target yield strength. Surface residual stress resulting from AWJP was compressive and ranged from 500 to 2500 MPa, and the depth of compressive residual stress ranged from nearly 80 to 600 mum. While the elastic prestress had no effect on the surface texture, it was a primary contributor to the magnitude of surface residual stress, which increased with an increase in the elastic prestress. The boundary conditions used to apply the prestress were found to be important to the residual stress field. Load control flexure prestress resulted in larger surface and subsurface compressive residual stress when compared to the displacement control flexure prestress. A finite element analysis of the treatment was used to explore the potential for using alternate prestress configurations to improve the residual stress distributions and to develop an understanding of the treatment mechanics. Three different prestress conditions (flexure, axial and biaxial loading) were simulated on a Ti6Al4V target subjected to a single impact. Each condition was studied under both load and displacement control boundary conditions. The finite element evaluations identified two mechanisms (plasticization and superposition) that contributed to the increase in magnitude and changes in shape of the residual stress field in treatments with elastic prestress. Overall, application of elastic prestress resulted in a 100% and 40% increase in the compressive surface residual stress and maximum residual stress and a 25% increase in the depth of compressive residual stress. The responses were influenced by the prestress distribution and in all cases load control prestress had a larger influence when compared to the displacement control. Results of the finite element model indicated that a biaxial prestress incorporating a combination of compressive and tensile components could be used to further improve the residual stress characteristics resulting from particle-based surface treatments. According to the results of this study, AWJP with elastic prestress can serve as a viable method of surface treatment in situations that require an increase in surface roughness and a compressive residual stress. The current study has showed that elastic prestress could be used as a design variable to achieve a desired subsurface residual stress distribution in particle-based surface treatments. Keywords: abrasive waterjet, elastic prestress, finite element model, residual stress.

  16. 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...

  17. Stress og aldring

    DEFF Research Database (Denmark)

    JØrgensen, Anders; JØrgensen, Martin Balslev

    2012-01-01

    Accumulating evidence supports the popular notion that psychological stress states may accelerate aging. Stress has been shown to influence cellular systems known to be involved in the aging process. Furthermore, stress is associated with an increased risk of various age-related medical disorders. These effects are likely mediated by the secretion of stress hormones. In this short review we focus on biochemical and epidemiological evidence for a link between stress and aging.

  18. 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.

  19. Effect of large mechanical stress on the magnetic properties of embedded Fe nanoparticles

    Directory of Open Access Journals (Sweden)

    Srinivasa Saranu

    2011-06-01

    Full Text Available Magnetic nanoparticles are promising candidates for next generation high density magnetic data storage devices. Data storage requires precise control of the magnetic properties of materials, in which the magnetic anisotropy plays a dominant role. Since the total magneto-crystalline anisotropy energy scales with the particle volume, the storage density in media composed of individual nanoparticles is limited by the onset of superparamagnetism. One solution to overcome this limitation is the use of materials with extremely large magneto-crystalline anisotropy. In this article, we follow an alternative approach by using magneto-elastic interactions to tailor the total effective magnetic anisotropy of the nanoparticles. By applying large biaxial stress to nanoparticles embedded in a non-magnetic film, it is demonstrated that a significant modification of the magnetic properties can be achieved. The stress is applied to the nanoparticles through expansion of the substrate during hydrogen loading. Experimental evidence for stress induced magnetic effects is presented based on temperature-dependent magnetization curves of superparamagnetic Fe particles. The results show the potential of the approach for adjusting the magnetic properties of nanoparticles, which is essential for application in future data storage media.

  20. Biaxial bending of slender HSC columns and tubes filled with concrete under short- and long-term loads: II) Verification / Flexión biaxial de las columnas esbeltas de concreto en alta resistencia y los tubos llenos de concreto bajo cargas a corto y largo plazo: Verificación

    Scientific Electronic Library Online (English)

    J. A, Rodríguez-Gutiérrez; J. D, Aristizabal-Ochoa.

    2014-12-01

    Full Text Available En un artículo adjunto se presenta el método analítico para calcular las respuestas, a corto y largo plazo, de las columnas esbeltas de concreto en alta resistencia (HSC) y de los tubos rellenos de hormigón; con condiciones de apoyo generalizados, sometidos a cargas transversales de luz y a cargas a [...] xiales excéntricas en los extremos (causando curvatura simple o doble bajo flexión uniaxial o biaxial). Los tipos de columnas que pueden ser analizadas son: ovaladas, rectangulares, circulares, C, T, L o de cualquier sección transversal arbitraria, sólida o hueca, además, las que están hechas de tubos de acero circulares y rectangulares llenos de concreto en alta resistencia. En esta publicación se presenta la validez del método y los resultados obtenidos son comparados con otros, que han sido reportados por diferentes investigadores en la literatura técnica, con más de setenta muestras de columnas. Abstract in english An analytical method that calculates both the short- and long-term response of slender columns made of high-strength concrete (HSC) and of tubes filled with concrete with generalized end conditions that are subjected to transverse loads along the span and to axial loads at the ends (causing single- [...] or double-curvature under uniaxial or biaxial bending) is presented in a companion paper. The columns that can be analyzed with this method include those with solid and hollow (rectangular, circular, oval, C-, T-, L-, or any arbitrary shape) cross sections and columns made of circular and rectangular steel tubes filled with HSC. In this paper, the validity of the proposed method is tested against experimental results from the technical literature that examined over seventy column specimens.

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

    International Nuclear Information System (INIS)

    Mechanically strengthened, highly cube textured Ni-7 at.%W/Ni-12 at.%W multi-layer substrates developed for coated conductors have been prepared by the advanced spark plasma sintering technique. The key innovation for developing this weakly magnetic and reinforced substrate was to use a new powder metallurgy and sintering route to bond multi-layers of Ni7W/Ni12W/Ni7W together in order to get an initial ingot, followed by the optimized cold working and annealing. Particular efforts were made in view of the optimization of the design, pressing as well as the heat treatment processes of the starting ingots to obtain a chemically gradient composite bulk, thus ensuring the subsequent cold deformation. The produced composite substrates have a strong {100} texture on Ni7W outer layers. The percentage of the biaxially orientated grains within a misorientation angle of 10 deg. is as high as 97.5%, while the length percentage of low-angle grain boundaries ranging from 2 deg. to 10 deg. in the composite substrate reaches 87.2%. Moreover, the yield strength ?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

  2. 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.

  3. 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.

  4. Effect of Low-Pressure Nitrogen DC Plasma Treatment on the Surface Properties of Biaxially Oriented Polypropylene, Poly (Methyl Methacrylate) and Polyvinyl Chloride Films

    International Nuclear Information System (INIS)

    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. (plasma technology)

  5. Biaxial alignment of high-Tc superconductor polycrystals VIII: Phi scan analysis of EuBa2Cu3O7-? (Eu-123)

    International Nuclear Information System (INIS)

    To reduce grain boundary weak links due to large-angle grain orientation mismatch, bulk (thick film) EuBa2Cu3O7-? high-Tc superconductor specimens were biaxially aligned by a mechanical force such that their [001] axes were perpendicular to the specimen surfaces and by a magnetic force so as to orient their [010] axes to lie parallel to the magnetic field direction in the specimen plane. We describe here the characterization of such EuBa2Cu3O7-? thick films by ? XRD scans of (013) reflections, demonstrating a high degree (33%) of c-axis alignment with FWHM of <5 degree and approximately Gaussian distributions of a,b-axis alignment with a FWHM of 47 degree. The formation of open-quote open-quote granular single crystals close-quote close-quote toward which this work is a further advance, can be seen as establishing a new paradigm in ceramics science. copyright 1996 Materials Research Society

  6. The effect of biaxial mechanical strain on the physical properties of double perovskite Sr2FeMoO6: A theoretical study

    Science.gov (United States)

    Lu, Ruifeng; Wu, Haiping; Qian, Yan; Kan, Erjun; Liu, Yuzhen; Tan, Weishi; Xiao, Chuanyun; Deng, Kaiming

    2014-08-01

    Using the density-functional theory, the effect of biaxial mechanical strain on the electronic and magnetic properties of double perovskite oxide Sr2FeMoO6 has been studied. Our calculations reveal that Sr2FeMoO6 exhibits a magnetic transition from ferrimagnetic to ferromagnetic phase in the strain region of 7-8%, accompanied by a spin crossover of Mo ion from intermediate-spin to low-spin state. For the ferrimagnetic Sr2FeMoO6, the electronic configuration of Fe ion shows a spin transition from high-spin to intermediate-spin state around the strain of -7% to -6%, causing a steep decrease of the magnetic moment from ~3.9 to ~2.3 ?B. Additionally, the half-metallic nature of Sr2FeMoO6 persists in the whole range of strain applied in this work. The results may expand the technology application of Sr2FeMoO6 in the spintronic field.

  7. 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.

  8. Stress at Work Place

    OpenAIRE

    Mohammad A. Shahrour

    2010-01-01

    One of hardest forms of stresses to avoid is that work place or job stress Job stress refers to stress experienced by an individual at or because of issues at their work place The term work related stress has many meanings and it causes different levels of anxiety. Not all challenges at work can be called stress as some of these challenges drive employees upward, and empower them to learn new skills or push them to work harder to achieve a certain goal. So, this type of challenges cannot be c...

  9. [Stress in physiological studies].

    Science.gov (United States)

    Filaretova, L P

    2010-09-01

    The review focuses on the concept of biological stress pioneered by Hans Selye, who demonstrated a key involvement of the pituitary-adrenocortical axis in the response to stress. It discusses the historic background of development of the stress concept and some aspects of modern physiological researches related to stress-induced activation of the hypothalamic-pituitary-adrenocortical axis. We focus mainly on the results demonstrating that stress-induced activation of the hypothalamic-pituitary-adrenocortical axis is a gastroprotective component of stress response. PMID:21254538

  10. 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.

  11. Stress and Heart Health

    Science.gov (United States)

    ... stress is a good idea for your overall health, and researchers are currently studying whether managing stress is effective for heart disease. A few studies have examined how well treatment or therapies work ...

  12. 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, ...

  13. Stress and Pregnancy

    Science.gov (United States)

    ... the person may be doing to relieve the stress such as poor eating habits, smoking cigarettes, drinking alcohol or abusing drugs. For now, it is unknown if stress itself increases the risk for pregnancy complications. Will ...

  14. Personality and stress.

    Science.gov (United States)

    Vollrath, M

    2001-09-01

    Recent years have witnessed an upsurge of interest in how personality affects the stress process. This paper reports on a broad spectrum of findings on the relationships between personality and stress, taking transactional stress theory as the point of departure. A first part outlines the different approaches stress research has taken within personality psychology as opposed to research based on transactional stress theory and discusses the debate between these two paradigms. The second part gives an overview of empirical findings, with a focus on the Big Five personality factors, in order to demonstrate that personality affects the stress process in every aspect. The discussion suggests that we address unresolved problems of transactional stress research in the framework of interactionist personality psychology. Special attention ought to be given to developing a better understanding of situational characteristics, stress-producing mechanisms, and the functions of situational choices and coping strategies for personality. PMID:11547909

  15. Cancer and Stress

    Science.gov (United States)

    ... Cancers Ovarian Cancer Cancer and Stress Cancer and Stress To deal with cancer, you also need to ... Debut CD “No Evidence of Disease” on Motéma Music, Sept. 8, 2009 Press Release: Expert Contributes to ...

  16. Stress and hormones

    OpenAIRE

    Ranabir, Salam; Reetu, K.

    2011-01-01

    In the modern environment one is exposed to various stressful conditions. Stress can lead to changes in the serum level of many hormones including glucocorticoids, catecholamines, growth hormone and prolactin. Some of these changes are necessary for the fight or flight response to protect oneself. Some of these stressful responses can lead to endocrine disorders like Graves’ disease, gonadal dysfunction, psychosexual dwarfism and obesity. Stress can also alter the clinical status of many pr...

  17. Occupational Stress Management

    OpenAIRE

    Mihaela STOICA; Florin BUICU

    2010-01-01

    The problem of occupational stress has been extensively studied mainly due to the negative effects it has on the organization and employees. Some organizations have programs designed to help physical and mental health workers to prevent problems due to stress and to help "make do" with work-related stress. Stress management is an important part of maintaining good physical and emotional health and healthy relationships with others. This article presents some strategies to prevent and reduce s...

  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. Stress og insomni

    DEFF Research Database (Denmark)

    Jennum, Poul; Zachariae, Bobby

    2012-01-01

    Insomnia and stress are two conditions, which are strongly associated and appear to be pathophysiologically integrated: the occurrence of stress increases the risk of insomnia, insomnia exacerbates stress, and coexistence of both factors has a negative influence on their prognosis. Stress and insomnia thus share complex interactions and the mechanisms involved are insufficiently understood but involve both psychological and physiological processes. First choice interventions involve behavioural and cognitive strategies and, to a lesser extent, pharmacological treatment.

  20. Stress, norepinephrine and depression.

    OpenAIRE

    Leonard, B.E.

    2001-01-01

    Stress is an important precipitant factor in depression, and the changes in various body systems that occur in depression are similar to those observed in response to stress. This paper discusses the interactions among the immune, endocrine and norepinephrine systems that are evident in patients with depression, as well as those affected by stress. Many of the stress-induced changes can be reversed by antidepressants, particularly norepinephrine reuptake inhibitors.

  1. 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.

  2. Stress and Mood

    Science.gov (United States)

    ... Read full story: Present Tense: Your Body, Your Mind, and Stress >> share Good-for-You Stress Busters Read full story: Good-for-You Stress Busters >> share Signs of Depression Read full story: Signs of Depression >> share Taking Control of Depression Read full story: Taking Control of ...

  3. Stress and Your Heart

    Medline Plus

    Full Text Available ... gov/medlineplus/videos/news/Stress_Heart_043015.html Stress and Your Heart HealthDay News Video - April 30, ... on this page, please enable JavaScript. Play video: Stress and Your Heart For closed captioning, click the ...

  4. Stress and Your Heart

    Medline Plus

    Full Text Available ... news/Stress_Heart_043015.html Stress and Your Heart HealthDay News Video - April 30, 2015 To use ... please enable JavaScript. Play video: Stress and Your Heart For closed captioning, click the CC button on ...

  5. Posttraumatic Stress Disorder

    Science.gov (United States)

    ... and Symptoms People with PTSD have symptoms of stress , anxiety , and depression that include any of the following: Intrusive thoughts ... Date Rape If Your Child Is Raped Childhood Stress About Teen Suicide Anxiety, Fears, and Phobias Depression Obsessive-Compulsive Disorder Five Steps for Fighting Stress ...

  6. Psychological Stress and Cancer

    Science.gov (United States)

    ... common cold and to have headaches, sleep trouble, depression, and anxiety. Can psychological stress cause cancer? Although stress can cause a number ... Social support in a group setting Medications for depression or ... how cancer patients can cope with stress can be found in the PDQ® summaries listed ...

  7. Voltage controlled biaxial strain in VO{sub 2} films grown on 0.72Pb(Mg{sub 1?3}Nb{sub 2?3})-0.28PbTiO{sub 3} crystals and its effect on the transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Petraru, A., E-mail: apt@tf.uni-kiel.de; Soni, R.; Kohlstedt, H. [Nanoelektronik, Technische Fakultät, Christian-Albrechts-Universität zu Kiel, Kiel 24143 (Germany)

    2014-09-01

    Vanadium oxide thin films (VO{sub 2}) were deposited on 0.72Pb(Mg{sub 1?3}Nb{sub 2?3})-0.28PbTiO{sub 3} (PMN-PT) crystalline substrates using pulsed laser deposition method. Due to their huge piezoelectric coefficients in the order of 2500?pm/V, the PMN-PT substrates are used to impose additional amount of biaxial strain to the VO{sub 2} films by applying an external bias to the substrates. The influence of the biaxial strain on the transition temperature and on the conductive properties of the VO{sub 2} films is investigated in this work. Thus, a change in the biaxial strain of ?0.8?×?10{sup ?3} applied in the (110) plane of the rutile cell of the VO{sub 2} lowered the metal-to-insulator transition temperature by 1.35?°C.

  8. 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.

  9. Coping with stress

    OpenAIRE

    Salmaani Barough N; Taghavi Larijani T; Monjamed Z; Sharifi N; Bahrani N

    1992-01-01

    Introduction: Stress is a complex and physiologic phenomenon that sometimes can be a source of problem. If an individual could not cope with stress, it would be a threat to physical and psychological health. Inclination to cope with stress is a positive way which helps one to improve his/her health. Materials and Methods: This research is a quasi-experimental study with the aim of determining the effect of education of methods of coping with stress on rate of stress among women working at Teh...

  10. Neuropeptide Y and Stress

    Directory of Open Access Journals (Sweden)

    Murat Gulsun

    2012-03-01

    Full Text Available The neurobiological aspects of stress and coping skills has been the focus of interest for many researchers. Some of the studies has shown that there is a significant relationship among genetically variables, stress response and life events. Neuropeptide Y is one of the systems regulating the stress response. Under the prolonged or repeated trauma neuropeptide Y is released from the brain's key areas. This system shows different levels of functioning in individuals with different levels of resilience. There is particular interest in the variations of genes that encode stress-sensitive signaling molecules during gene-environment interaction. This condition may contribute to susceptibility of stress or stress resilience. Neuropeptide Y system plays a key role in the adaptation to behavioral stress. The reduced levels of neuropeptide Y have also been observed in treatment-resistant depression and posttraumatic stress disorder. Lower level of neuropeptide Y expression and dysfunctional neuropeptide Y system in response to stress and resulting decreased stress resilience could increase susceptibility to stress-related disorders.

  11. Growth of thin Al{sub 2}O{sub 3} films on biaxially oriented polymer films by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Vaehae-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Kauppi, Emilia, E-mail: emilia.kauppi@vti.fi [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Sahagian, Khoren, E-mail: khoren@anasysinstruments.com [Anasys Instruments, 121 Gray Avenue, Suite 100, Santa Barbara, CA 93101 (United States); Johansson, Leena-Sisko, E-mail: leena-sisko.johansson@aalto.fi [Aalto University, School of Chemical Technology, Department of Forest Products Technology, P.O. Box 16100, FI-00076 AALTO (Finland); Peresin, Maria Soledad; Sievaenen, Jenni; Harlin, Ali [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland)

    2012-11-01

    The effects of thin film nucleation and initial growth on roughness, chemistry and thermomechanical properties of polymer film surfaces were studied. Al{sub 2}O{sub 3} was deposited onto commercial biaxially oriented polypropylene and polylactic acid films at 80 Degree-Sign C by using atomic layer deposition technique. Both substrates, especially the more hydrophobic polypropylene, showed initial growth through Al{sub 2}O{sub 3} clusters. There was a faster deposition of Al{sub 2}O{sub 3} on polylactic acid film than on polypropylene at the early stages of the Al{sub 2}O{sub 3} deposition. There were also indications of chemical interactions between polylactic acid and trimethyl aluminum used as a precursor for Al{sub 2}O{sub 3}. Changes in the thermo-mechanical properties of the polymer surfaces with Al{sub 2}O{sub 3} also evidenced the differences between the substrate polymer films. The near surface interphase formed in polylactic acid probably contributed to the strong increase and scattering in the softening temperature during the early thin film growth. - Highlights: Black-Right-Pointing-Pointer Growth of atomic layer deposited Al{sub 2}O{sub 3} at 80 Degree-Sign C was studied on commercial films. Black-Right-Pointing-Pointer Both substrate films showed early Al{sub 2}O{sub 3} growth through clusters. Black-Right-Pointing-Pointer Initial growth rate depends on the nature of the substrate film surface. Black-Right-Pointing-Pointer There were indications of chemical interactions between substrate and precursor. Black-Right-Pointing-Pointer Film thickness and chemical interactions affect thermo-mechanical properties.

  12. 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

  13. Bone stress injuries

    Energy Technology Data Exchange (ETDEWEB)

    Kiuru, M.J.; Pihlajamaeki, H.K.; Ahovuo, J.A. [Helsinki Univ. Central Hospital (Finland). Dept. of Radiology

    2004-05-01

    Bone stress injuries are due to cyclical overuse of the bone. They are relatively common in athletes and military recruits but also among otherwise healthy people who have recently started new or intensive physical activity. Diagnosis of bone stress injuries is based on the patient's history of increased physical activity and on imaging findings. The general symptom of a bone stress injury is stress-related pain. Bone stress injuries are difficult to diagnose based only on a clinical examination because the clinical symptoms may vary depending on the phase of the pathophysiological spectrum in the bone stress injury. Imaging studies are needed to ensure an early and exact diagnosis, because if the diagnosis is not delayed most bone stress injuries heal well without complications.

  14. Stress Management and Gifted Children

    Science.gov (United States)

    Patel, Vidisha A.

    2009-01-01

    Stress can affect anyone, and gifted children are no exception. Giftedness can sometimes be the cause of the stress. Perfectionism, sensitivity, and intensity are characteristics of gifted children that may exacerbate stress. Stress can be constructive. Prolonged stress, however, with no time to recover becomes detrimental. Continued stress upsets…

  15. 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…

  16. Development and application of a material law for steel-fibre-reinforced concrete with regard to its use for pre-stressed concrete reactor vessels

    International Nuclear Information System (INIS)

    On the basis of the evaluation of many publications on the mechanical behaviour of steel fibre reinforced concrete (SFRC) and on the results of experiments using an SFRC especially developed for pre-stressed concrete reactor vessels (PCRVs), a material law for SFRC including general multiaxial stress conditions has been developed. From fibre pull-out tests described in the literature and by use of the experimental results, relations describing the capable tensile stress in SFRC after cracking, as a function of crack width, have been derived. There is a significant increase in the biaxial compressive strength of SFRC compared with plain concrete. The improved behaviour under multiaxial stress conditions, with one of the principal stresses being tensile, is outlined in comparison with different formulations of failure envelopes of plain concrete. For the purpose of verifying the material law implemented in the computer program used, analyses have been carried out for experiments with SFRC beams. After some modification concerning the shear behaviour, load-displacement curves and realistic crack propagations which correspond well have been obtained. In the stand-tube area in the centre of a PCRV top cap the use of SFRC is advantageous because of the difficulties concerning the arrangement of reinforcement in the concrete between the tubes. (orig.)

  17. 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)

  18. Stress evolution during growth of GaN (0001)/Al2O3(0001) by reactive dc magnetron sputter epitaxy

    International Nuclear Information System (INIS)

    We study the real time stress evolution, by in situ curvature measurements, during magnetron sputter epitaxy of GaN (0?0?0?1) epilayers at different growth temperatures, directly on Al2O3(0?0?0?1) substrates. The epilayers are grown by sputtering from a liquid Ga target in a mixed N2/Ar discharge. For 600 °C, a tensile biaxial stress evolution is observed, while for 700 °C and 800 °C, compressive stress evolutions are observed. Structural characterization by cross-sectional transmission electron microscopy, and atomic force microscopy, revealed that films grew at 700 °C and 800 °C in a layer-by-layer mode while a growth temperature of 600 °C led to an island growth mode. High resolution x-ray diffraction data showed that edge and screw threading dislocation densities decreased with increasing growth temperature, with a total density of 5.5 × 1010 cm?2 at 800 °C. The observed stress evolution and growth modes are explained by a high surface mobility during magnetron sputter epitaxy at 700–800 °C. Other possible reasons for the different stress evolutions are also discussed. (paper)

  19. STRESS - STRAIN CURVE ANALYSIS OF WOVEN FABRICS MAD E FROM COMBED YARNS TYPE WOOL

    Directory of Open Access Journals (Sweden)

    VÎLCU Adrian

    2014-05-01

    Full Text Available The paper analyses the tensile behavior of woven fabrics made from 45%Wool + 55% PES used for garments. Analysis of fabric behavior during wearing has shown that these are submitted to simple and repeated uni-axial or bi-axial tensile strains. The level of these strains is often within the elastic limit, rarely going over yielding. Therefore the designer must be able to evaluate the mechanical behavior of such fabrics in order to control the fabric behavior in the garment. This evaluation is carried out based on the tensile testing, using certain indexes specific to the stress-strain curve. The paper considers an experimental matrix based on woven fabrics of different yarn counts, different or equal yarn count for warp and weft systems and different structures. The fabrics were tested using a testing machine and the results were then compared in order to determine the fabrics’ tensile behavior and the factors of influence that affect it.From the point of view of tensile testing, the woven materials having twill weave are preferable because this type of structure is characterized by higher durability and better yarn stability in the fabric. In practice, the woven material must exhibit an optimum behavior to repeated strains, flexions and abrasions during wearing process. The analysis of fabrics tensile properties studied by investigation of stress-strain diagrams reveals that the main factors influencing the tensile strength are: yarns fineness, technological density of those two systems of yarns and the weaving type.

  20. Biaxial strain-modified valence and conduction band offsets of zinc-blende GaN, GaP, GaAs, InN, InP, and InAs, and optical bowing of strained epitaxial InGaN alloys

    Science.gov (United States)

    Kent, P. R. C.; Hart, Gus L. W.; Zunger, Alex

    2002-12-01

    Using density-functional calculations, we obtain the (001) biaxial strain dependence of the valence and conduction band energies of GaN, GaP, GaAs, InN, InP, and InAs. The results are fit to a convenient-to-use polynomial and the fits provided in tabular form. Using the calculated biaxial deformation potentials in large supercell empirical pseudopotential calculations, we demonstrate that epitaxial strain reduces the InGaN alloy bowing coefficient compared to relaxed bulk alloys.

  1. Effect of stress-triaxiality on void growth in dynamic fracture of metals: a molecular dynamics study

    CERN Document Server

    Seppälä, E T; Rudd, R E

    2004-01-01

    The effect of stress-triaxiality on growth of a void in a three dimensional single-crystal face-centered-cubic (FCC) lattice has been studied. Molecular dynamics (MD) simulations using an embedded-atom (EAM) potential for copper have been performed at room temperature and using strain controlling with high strain rates ranging from 10^7/sec to 10^10/sec. Strain-rates of these magnitudes can be studied experimentally, e.g. using shock waves induced by laser ablation. Void growth has been simulated in three different conditions, namely uniaxial, biaxial, and triaxial expansion. The response of the system in the three cases have been compared in terms of the void growth rate, the detailed void shape evolution, and the stress-strain behavior including the development of plastic strain. Also macroscopic observables as plastic work and porosity have been computed from the atomistic level. The stress thresholds for void growth are found to be comparable with spall strength values determined by dynamic fracture exper...

  2. The relationship between stress and photoluminescence of Cd0.96Zn0.04Te single crystal

    International Nuclear Information System (INIS)

    Photoluminescence (PL) and high-resolution X-ray diffraction (HRXRD) experiments have been carried out on strained Cd0.96Zn0.04Te single crystals to reveal the correlation between luminescence spectrum and stress in CdZnTe wafers. The tensile stress introduced by quenching was measured by X-ray diffraction methods. The photoluminescence spectra were found to move to higher energies, and the intensity of neutral donor bound exciton (D0, X) peak of CdZnTe wafer was increased after quenching. The reasons for these variations are suggested to be determined by the change of the energy band gap Eg of the CdZnTe wafer and the increase of crystal defects. The in-plane biaxial stress of 1 GPa results in a shift of the excitonic PL spectrum of 7.05-12.03 meV. In particular, the tensile strain reduces the formation energy of TeCd antisite defects, which are the shallow donors located at 0.01 eV below the conduction band. Therefore, high density of TeCd antisite defects demonstrated by the higher (D0, X) emission are generated due to the high tensile strain in the quenched specimen

  3. Martensitic transformation under stress

    International Nuclear Information System (INIS)

    Thermodynamics considerations of martensitic transformation under stress are considered. The equation for dM s/d? established by Patel and Cohen is discussed taking account of the grain size effect in polycrystalline materials, i.e. the orientation preference effect and the interaction between grain boundary and applied stress. A general model for the calculation of Ms temperature in the face centered cubic to body centered cubic (fcc ? bcc(bct)) transformation influenced by stress in iron based alloys is proposed. Quantitative descriptions of strain effects on nucleation rate or nucleation barrier, activation energy and morphology, as well as the effect of internal stress on autocatalytic nucleation of martensitic transformation are briefly reviewed. The modeling of martensitic transformation under stress, involving modeling of the motion of martensite/parent interface and reorientation of martensite under stress is reviewed

  4. Bone stress injuries; Stressfrakturen

    Energy Technology Data Exchange (ETDEWEB)

    Geiger, Julia [Universitaetsklinik Freiburg (Germany). Abt. fuer Diagnostische Radiologie; Rottenburger, Christof [Universitaetsklinik Freiburg (Germany). Abt. Nuklearmedizin; Uhl, Markus [Regionalverbund kirchlicher Krankenhaeuser (RkK), Freiburg (Germany). St. Josefskrankenhaus, Abt. Radiologie

    2010-03-15

    Bone stress injuries are due to cyclical overuse of skeleton. Stress-related bone injuries are quite common among otherwise healthy persons who have recently started new or intensive physical activity. Diagnosis is based on a typical patient's history and imaging findings. Conventional radiography serves as the primary imaging modality when a stress injury is suspected clinically. In the case of negative or atypical findings, the diagnosis should be confirmed with MRI rather than with bone scintigraphy. (orig.)

  5. Stress, Sleep, and Allergy

    OpenAIRE

    Jernelo?v, Susanna

    2010-01-01

    Allergic diseases have recently increased dramatically in the western world, now affecting about 30% of the Swedish population. The reasons for this increase are unclear, but some of the suspects are behavioral factors, such as stress and sleep. Problems with stress are also common today, and stress may change the set-points for the functioning of the body, for instance in the immune system. Sleep, on the other hand, is important for recuperation, and disturbed sleep acts a ...

  6. Women, work and stress

    OpenAIRE

    Evolahti, Annika

    2012-01-01

    Work-related stress has become a major public health problem in Western societies. In Sweden women account for the majority of long-term sick leave and the most common reasons are psychiatric conditions such as depression and stress-related diagnoses. Stressful working conditions have been shown to influence both physical and psychological health by acting as important mediating factors in the development of e.g. cardiovascular and musculoskeletal disorders and symptoms of depr...

  7. Stress, Epigenetics, and Alcoholism

    OpenAIRE

    Moonat, Sachin; Pandey, Subhash C.

    2012-01-01

    Acute and chronic stressors have been associated with alterations in mood and increased anxiety that may eventually result in the development of stress-related psychiatric disorders. Stress and associated disorders, including anxiety, are key factors in the development of alcoholism because alcohol consumption can temporarily reduce the drinker’s dysphoria. One molecule that may help mediate the relationship between stress and alcohol consumption is brain-derived neurotrophic factor (BDNF),...

  8. 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...

  9. Stress and Brain Atrophy

    OpenAIRE

    Bremner, J. Douglas

    2006-01-01

    Studies in animals showed that stress is associated with changes in hippocampal function and structure, an effect mediated through decreased neurogenesis, increased glucocorticoids, and/or decreased brain derived neurotrophic factor. Antidepressants and some anticonvulsants block the effects of stress and/or promote neurogenesis in animal studies. Patients with posttraumatic stress disorder (PTSD) have been shown to have smaller hippocampal volume on magnetic resonance imaging and deficits in...

  10. Stresses in lipid membranes

    OpenAIRE

    Capovilla, Riccardo; Guven, Jemal

    2002-01-01

    The stresses in a closed lipid membrane described by the Helfrich hamiltonian, quadratic in the extrinsic curvature, are identified using Noether's theorem. Three equations describe the conservation of the stress tensor: the normal projection is identified as the shape equation describing equilibrium configurations; the tangential projections are consistency conditions on the stresses which capture the fluid character of such membranes. The corresponding torque tensor is als...

  11. Dealing with stress.

    International Nuclear Information System (INIS)

    Office support has been identified as one of the five most stressful occupations, the main factor being that administrative staff get the impression that they have no control over their stressors. This video assists viewers in identifying stress and in dealing with it in a way that does not interfere with the ability to be productive. It suggests techniques for turning stress into motivation for positive achievement.

  12. Dynorphin, stress, and depression

    OpenAIRE

    Knoll, Allison T.; Carlezon, William A

    2009-01-01

    Stress is most often associated with aversive states. It rapidly induces the release of hormones and neuropeptides including dynorphin, which activates kappa opioid receptors (KORs) in the central and peripheral nervous systems. In animal models, many aversive effects of stress are mimicked or exacerbated by stimulation of KORs in limbic brain regions. Although KOR signaling during acute stress may increase physical ability (by producing analgesia) and motivation to escape a threat (by produc...

  13. Plant abiotic stress signaling

    OpenAIRE

    Akpinar, B. Ani; Avsar, Bihter; Lucas, Stuart J.; Budak, Hikmet

    2012-01-01

    Stress signaling is central to plants which—as immobile organisms—have to endure environmental fluctuations that constantly interfere with vigorous growth. As a result, plant-specific, elaborate mechanisms have evolved to perceive and respond to stress conditions. Currently, these stress responses are plausibly being revealed to involve crosstalks with energy signaling pathways as any growth-limiting factor alters plant’s energy status. Among these, autophagy, conventionally regarded as...

  14. Oxidative Stress in Neurodegeneration

    OpenAIRE

    Pant, Harish C.; Mishra, Santosh K.; Varsha Shukla

    2011-01-01

    It has been demonstrated that oxidative stress has a ubiquitous role in neurodegenerative diseases. Major source of oxidative stress due to reactive oxygen species (ROS) is related to mitochondria as an endogenous source. Although there is ample evidence from tissues of patients with neurodegenerative disorders of morphological, biochemical, and molecular abnormalities in mitochondria, it is still not very clear whether the oxidative stress itself contributes to the onset of neurodegeneration...

  15. 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. ...

  16. 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.

  17. 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.

  18. 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,

  19. Stress: Concepts and applications

    International Nuclear Information System (INIS)

    The stress theorem determines the stress from the electronic ground state of any quantum system with arbitrary strains and atomic displacements. We derive this theorem in reciprocal space, within the local-density-functional approximation. The evaluation of stress, force and total energy permits, among other things, the determination of complete stress-strain relations including all microscopic internal strains. We describe results of ab-initio calculations for Si, Ge, and GaAs, giving the equilibrium lattice constant, all linear elastic constants cij and the internal strain parameter ?. (orig.)

  20. 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)

  1. 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

    International Nuclear Information System (INIS)

    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) (authors)

  2. 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

  3. 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.

  4. STRESS IN ORGANIZATIONS

    Directory of Open Access Journals (Sweden)

    Maria-Elena, GHEORDUNESCU

    2014-11-01

    Full Text Available Taking into account the changes that are currently taking place in our country, it is clear that these changes, which occur in almost all companies, lead to new stress factors for both employees and the organization. Occupational stress is a major problem for employees and managers, but also for the whole society. The issue of stress in organizations has given birth to many debates and studies. It is a common theme that is addressed by managers, employees and consultants from different perspectives. According to a study by the European Agency for Safety and Health at Work, in the European Union, work-related stress is the second work-related health issue after dorsal disorders. It affects 28% of EU employees. The European Parliament is fully involved in addressing issues related to the psychological support of the staff. Preventing work-related stress is one of the objectives set out in the Communique of the European Commission for Employment and Social Affairs regarding their new health and safety at work strategy. Manifestations of stress in organizations are easily observable, being manifested by behaviors such as: difficulties in adapting to the changes required to work or the dramatic drop in labor productivity. Also a double action is met: both the person who passes through the stressful situation and at the organization level on which it is reflected the existence of a stressful environment. This paper aims to address the implications of workplace stress, symptoms of stress in the workplace and strategies to eliminate and prevent stress at work This paper represents an exploratory research based on qualitative methods, being consulted various sources of information: the literature, case studies, media articles, reports of relevant organizations, etc.

  5. 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.

  6. Informational stress: discussion paper.

    OpenAIRE

    Restian, A.

    1990-01-01

    Stress can be caused by a multitude of factors requiring the capacity for adaption by the organism. As well as physical, chemical and biological factors, information may also become a stressor in certain circumstances. Stress may be induced just as well by too little as by too much information, and by the quality of the information.

  7. Leveraging Stress Level

    OpenAIRE

    Mitali PATHAK

    2011-01-01

    Stress is a costly business expense that affects both employee health and company profits. At the backdrop of this, the present research study is an attempt to explore and analysis the findings of the research studies which have been concluded in resolving and managing conflict arising through variances in stress level at the organizational hierarchy.

  8. 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.

  9. 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)

  10. Stress detection in plants

    Science.gov (United States)

    How can the status of plant stress be measured rapidly and accurately in the hundreds of trees managed within a commercial orchard? Two technologies have been developed over the past two decades that will provide useful information to detect plant stress in orchard systems: 1) Reflectance of visibl...

  11. Release from Stress.

    Science.gov (United States)

    Gmelch, Walter H.

    An overview of the most recent ideas on managerial stress is presented along with worksheets and exercises for a program to help educational administrators, their staffs, and secretaries cope with and reduce organizational and personal stress. Research cited includes the author's survey of 1,200 Oregon school administrators and over 200…

  12. 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

  13. 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.

  14. Stress studies in EFG

    Science.gov (United States)

    1982-01-01

    A program to study stress generation mechanisms in silicon sheet growth was started. The purpose of the research is to define post-growth temperature profiles for the sheet that can minimize its stress during growth at high speeds, e.g., greater than 3 cm/min. The initial tasks described concern work in progress toward the development of computing capabilities to (1) model stress-temperature relationships in steady-state ribbon growth, and (2) provide a means to calculate realistic temperature fields in ribbon, given growth system component temperatures as boundary conditions. If it is determined that low stress configurations can be achieved, the modeling is to be tested experimentally by constructing low-stress growth systems for EFG silicon ribbon.

  15. 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

  16. 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...

  17. 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.

  18. Stress Relief for the Caregiver

    Science.gov (United States)

    staying strong Stress relief for a caregiver the compassion to care, the leadership to conquer 2 1 Take care of yourself ... caregiver. 6 5 6 Manage your level of stress. Consider how stress affects your body (stomachaches, high ...

  19. Heat Stress Resources for Workers

    Science.gov (United States)

    ... Home Workplace Safety & Health Topics NIOSH Share Compartir HEAT STRESS Infographic: Protect your workers from HEAT STRESS ... and how it can be prevented. Types of Heat Stress Heat Stroke | Heat Exhaustion | Heat Syncope | Heat ...

  20. Stress reduction and the brain

    Science.gov (United States)

    2009-12-26

    Professor Bruce McEwen describes steps that can reduce stress, including sleep, exercise, and a healthy diet. The brain is the central organ of stress and differentiates positive, tolerable, and toxic stress.