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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

    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...

  2. 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.

  3. The Cladding Fracture Behaviour under Biaxial Stress Conditions

    International Nuclear Information System (INIS)

    It is considered that biaxial stress is generated in the cladding of high burnup fuels under reactivity initiated accident (RIA) conditions due to bonding between the fuel pellet and cladding and the isotropy of pellet thermal expansion. The effect of biaxiality on the fracture and deformation behaviour of the cladding has not been fully investigated even for unirradiated material, while it is well-known that the fracture behaviour strongly depends on the stress condition. Since such biaxial stress condition cannot be simulated by conventional mechanical testing techniques, a test apparatus was developed to control the axial and hoop stresses independently and evaluate the mechanical and fracture behaviour of the fuel cladding under biaxial stress conditions. This paper describes the outline of preliminary test results obtained under various biaxial stress conditions at room temperature using this apparatus. (author)

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

    OpenAIRE

    Bahai, S. Taylor; D. W. A. Rees

    2012-01-01

    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. The...

  5. Biaxial stress effects on estimating J under combined mechanical and thermal stresses

    International Nuclear Information System (INIS)

    In this paper, the applicability to bi-axial stress states of a simple approximation proposed in our previous work for quantifying the elastic-plastic J under combined primary and secondary stresses is investigated.To produce the bi-axial stress states, circumferential cracked pipes under combined pressure, axial tension (or compression) and thermal stresses are considered. The results suggest that the proposed approximation can be applied to bi-axial stress states, and is slightly more conservative for bi-axial mechanical stresses than for uni-axial ones. The degree of conservatism decreases with increasing strain hardening exponent and with increasing relative magnitude of secondary stress. - Highlights: ? A method to estimate J under combined primary and secondary stresses was proposed by the authors. ? This paper extends the proposed method to biaxial primary stress states. ? We find that the proposed approximation can be applied to bi-axial stress states. ? The proposed approximation is slightly more conservative for biaxial stresses than for uniaxial ones. ? The degree of conservatism decreases with increasing hardening exponent and relative magnitude of secondary stress.

  6. Mean stress effects in biaxial fatigue of Inconel 718

    International Nuclear Information System (INIS)

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

  7. Study on thermal fatigue endurance under biaxial stress state

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  9. 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

  10. Numerical analysis oriented biaxial stress-strain relation and failure criterion of plain concrete

    International Nuclear Information System (INIS)

    A biaxial stress-strain relation and failure criterion is proposed, which is applicable to structural analysis methods. The formulation of material behavior of plain concrete in biaxial stress-state was developed. A nonlinear elastic, anisotropic stress-strain relation was derived with two moduli of elasticity, E1, E2 and Poisson's ratios, ?1, ?2, which depend on the prevailing biaxial stress state. The stress-strain relation is valid in the whole biaxial stress field, that means with a smooth transition between the domains of tension/tension, tension/compression and compression/compression. The stress-dependent moduli E1, E2 and the Poisson's ratios ?1, ?2 are approximated by polynomials, trigonometrical and exponential functions. A failure criterion was defined by approximating the test results of the biaxial ultimate concrete strength with a 7th degree polynomial, which is also valid in the whole biaxial stress domain. The definition of the state of failure is given as a function of stresses as well as strains. Initial parameters of the formulation of the biaxial material behavior are the uniaxial cylindrical strength of concrete and the initial values of Young's modulus and Poisson's ratio. A simple expansion of this formulation makes it applicable not only to normal but also to light-weight concrete. Comparison of numerically calculated stress-strain curves up to the ultimate biaxial stresses which indicate the failure criteria with those obtained from tests show a very good agreement. It is shown, that the biaxial stress-strain relation can be extended for use in cases of triaxial tension/tension/compression stress state. Numerical examples of analysis of concrete slabs show the importance of incorporation of a realistic material behavior for better safety estimations

  11. Strength and deformation of sealed HTR-concrete under biaxial stresses and elevated temperatures

    International Nuclear Information System (INIS)

    Biaxial short term fracture tests at elevated temperature were performed on sealed basalt concrete specimens. These tests confirm that the strength and deformation characteristics are determined by the shared influence of the temperature as well as of the biaxial state of stress. (author)

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

    OpenAIRE

    Calixto José Marcio F.

    2002-01-01

    The results of an experimental investigation on the microcracking of high-performance concrete subjected to biaxial tension-compression stresses are presented. Short-term static tests and microcracking mapping were performed on 12.5 cm square by 1.25 cm thick plates. Strain controlled tests were executed in a biaxial testing machine constructed at the University of Texas. The primary variables studied were the deformations and the ultimate stress level at each stress ratio as well as the micr...

  13. Strain Energy Effects on Texture Evolution in Thin Films: Biaxial vs. Uniaxial Stress State

    International Nuclear Information System (INIS)

    Grain growth in thin films is usually accompanied by texture evolution due to the crystallographic dependencies of surface, interface and strain energies. In this work the driving forces for grain growth for a 1 and 5 ?m thick Cu thin film on a polyimide substrate are calculated assuming biaxial and uniaxial stress. While the results for the biaxial stress state are used to explain observed textures, for the case of uniaxial stress predictions suggest new ways to control the texture of thin films

  14. Strain Energy Effects on Texture Evolution in Thin Films: Biaxial vs. Uniaxial Stress State

    Science.gov (United States)

    Sonnweber-Ribic, P.; Dehm, G.; Gruber, P.; Arzt, E.

    2006-02-01

    Grain growth in thin films is usually accompanied by texture evolution due to the crystallographic dependencies of surface, interface and strain energies. In this work the driving forces for grain growth for a 1 and 5 ?m thick Cu thin film on a polyimide substrate are calculated assuming biaxial and uniaxial stress. While the results for the biaxial stress state are used to explain observed textures, for the case of uniaxial stress predictions suggest new ways to control the texture of thin films.

  15. Surface cracking in layers under biaxial, residual compressive stress

    International Nuclear Information System (INIS)

    Thin two-phase, Al2O3/t-Zr(3Y)O2 layers bounded by much thicker Zr(3Y)O2 layers were fabricated by co-sintering powders. After cooling, cracks were observed along the center of the two-phase, Al2O3/t-Zr(3Y)O2 layers. Although the Al2O3/t-Zr(3Y)O2 layers are under residual, biaxial compression far from the surface, tensile stresses, normal to the center line, exist at and near the surface. These highly localized tensile stresses can cause cracks to extend parallel to the layer, to a depth proportional to the layer thickness. A tunneling/edge cracking energy release rate function is developed for these cracks. It shows that for a given residual stress, crack extension will take place only when the layer thickness is greater than a critical value. A value of the critical thickness is computed and compared with an available experimental datum point. In addition, the behavior of the energy release rate function due to elastic mismatch is calculated via the finite element method (FEM). It is also shown how this solution for crack extension can be applied to explain cracking associated with other phenomena, e.g., joining, reaction couples, etc

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-01

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

  18. Method for measuring biaxial stress in a body subjected to stress inducing loads

    Science.gov (United States)

    Clotfelter, W. N. (inventor)

    1977-01-01

    A method is described for measuring stress in test articles including the steps of obtaining for a calibrating specimen a series of transit time differentials between the second wave echo for a longitudinal wave and the first wave echo for each of a pair of shear waves propagated through the specimen as it is subjected to known stress load of a series of stress loads for thus establishing a series of indications of the magnitudes for stress loads induced in the specimen, and thereafter obtaining a transit time differential between the second wave echo for a longitudinal wave and the first wave echo for each of a pair of shear waves propagated in the planes of the stress axes of a test article and comparing the transit time differential thus obtained to the series of transit time differentials obtained for the specimen to determine the magnitude of biaxial stress in the test article.

  19. Application of hysteresis modeling to magnetic techniques for monitoring biaxial stress

    Energy Technology Data Exchange (ETDEWEB)

    Sablik, M.J.; Burkhardt, G.L.; Kwun, H.

    1993-12-31

    A probe, consisting of two excitation coils and a detection coil wrapped around a core with a Hall probe between the pole pieces, has been used to measure indirectly the influence of biaxial stress on the magnetic properties of a ferromagnetic specimen, in this case annealed SAE-4130 steel. Properties measured indirectly included remanence, coercivity, and first, third and fifth harmonic amplitudes. The properties were extracted from the voltage measured across the detection coil and incorporate the magnetic influence of the soft iron core, but with the effect of air gap variation between pole piece and sample kept to a controlled range. Results were compared to a micromagnetic model for the effect of biaxial stress on hysteresis and on magnetic properties. The micromagnetic model is a modified version of a model previously employed by Schneider et al. The experimental remanence variation due to biaxial stress compared very well to the predictions of the model. Furthermore, the model predict,s and experiment bears out, that the remanence with the field along one stress axis minus the remanence with the field along the other stress axis falls in a straight-line band of values when plotted against the difference of the two stresses. This suggests a possible NDE technique for detecting differences in biaxial stresses at a given location in a steel specimen.

  20. Plastic deformation and fracture behavior of zircaloy-2 fuel cladding tubes under biaxial stress

    International Nuclear Information System (INIS)

    Various combinations of biaxial stress were applied on five batches of recrystallized zircaloy-2 fuel cladding tubes with different textures; elongation in both axial and circumferential directions of the specimen was measured continuously up to 5% plastic deformation. The anisotropic theory of plasticity proposed by Hill was applied to the resulting data, and anisotropy constants were obtained through the two media of plastic strain loci and plastic strain ratios. Comparison of the results obtained with the two methods proved that the plastic strain loci provide data that are more effective in predicting quantitatively the plastic deformation behavior of the zircaloy-2 tubes. The anisotropy constants change their value with progress of plastic deformation, and judicious application of the effective stress and effective strain obtained on anisotropic materials will permit the relationship between stress and strain under various biaxialities of stresses to be approximated by the work hardening law. The test specimens used in the plastic deformation experiments were then stressed to fracture under the same combination of biaxial stress as in the proceeding experiments, and the deformation in the fractured part was measured. The result proved that the tilt angle of the c-axis which serves as the index of texture is related to fracture ductility under biaxial stress. Based on this relationship, it was concluded that material with a tilt angle ranging from 100 to 150 is the most suitable for fuel cladding tubes, from the viewpoint of fracture ductility, at least in the case of unirradiated material. (auth.)

  1. 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.

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

    Science.gov (United States)

    Nolan, D R; McGarry, J P

    2016-01-01

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

  3. ADIABATIC SHEAR UNDER BIAXIAL STRESS CONDITIONS IN SHEET METAL FORMING PROCESSES

    OpenAIRE

    Luo, L; Dodd, B.

    1991-01-01

    A criterion for adiabatic shear instability under biaxial stress conditions is obtained using the results of a general three dimensional perturbation analysis of plastic flow developed by the authors. The criterion is then applied to dynamic sheet metal forming processes. The critical instability loci are obtained which are in good agreement with experimental data. Also the shear failure directions coincide with those predicted for instability.

  4. 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.

  5. 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)

  6. Ductility of Zircaloy canning tubes in relation to stress ratio in biaxial testing

    International Nuclear Information System (INIS)

    A biaxial-burst testing machine has been designed in which biaxial plane stress tests can be carried out on tubular material with any stress ratio in the range sigma/sub THETA/:sigma/sub z/ 4:5 to 2:1, where 2:1 implies the closed-end burst test. Unirradiated Zircaloy tubes cold worked 80 percent, recrystallized at 5750C, and characterized by a texture having a basal pole tilt angle of 33 deg were tested at room temperature with various stress ratios, namely, 4:5, 1:1, 5:4, 3:2, and 2:1. In addition, tension and open-end burst tests were carried out in conventional machines. The uniform ductility measured as uniform effective strain displays a minimum at the stress ratio 3:2. It has been found experimentally that the stress ratio for minimum uniform ductility corresponds to deformation under a plane strain loading condition, that is, the stress ratio which gives no change in the tube length

  7. Biaxial stress corrosion cracking of 316L stainless steel in MgCl2 (44%) at 154 deg C

    International Nuclear Information System (INIS)

    Stress corrosion cracking tests, under biaxial loading, of 316L austenitic stainless steel in a boiling MgCl2 (44 %) solution at 154 deg C, show that the multiaxial stress cracking criterion is different from the uniaxial criterion. The crack initiates at etch pits and does not necessarily grow perpendicular to the direction of the maximum principal stress. (authors)

  8. 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)

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

    Scientific Electronic Library Online (English)

    José Marcio F., Calixto.

    2002-09-01

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

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

    Directory of Open Access Journals (Sweden)

    Calixto José Marcio F.

    2002-01-01

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

  11. Shallow Flaws Under Biaxial Loading Conditions, Part II: Application of a Weibull Stress Analysis of the Cruciform Bend Specimen Using a Hydrostatic Stress Criterion

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-08-01

    Cruciform beam fracture mechanics specimensl have been developed in the Heavy Section Steel Technology (HSST) Program at Oak Ridge National Laboratory (ORNL) to introduce a prototypic, far- field, out-of-plane biaxird bending stress component in the test section that approximates the nonlinear biaxial stresses resulting from pressurized-thernxd-shock or pressure-temperature loading of a nuclear reactor pressure vessel (RPV). Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shtdlow, surface flaws. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. Two and three- parameter Weibull models have been calibrated using a new scheme (developed at the University of Illinois) that maps toughness data from test specimens with distinctly different levels of crack-tip constraint to a small scale yielding (SSY) Weibull stress space. These models, using the new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the OW integral definition, have been shown to correlate the experimentally observed biaxiaI effect in cruciform specimens, thereby providing a scaling mechanism between uniaxial and biaxial loading states.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-08-01

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

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

    International Nuclear Information System (INIS)

    In this paper, the case of Single Edge Notch (SEN) specimens subject to opening/compressive loading was analyzed; The loads are applied in several ratios to evaluate the influence of the specimen geometry, and the Stress Intensity Factor (SIF) K1 values on the directional stability of crack propagation. The main purpose of this work is to evaluate the behaviour of the fracture propagation, when modifying the geometry of the SEN specimen and different relationships of load tension/compression are applied. Additionally, the precision of the numerical and experimental analysis is evaluated to determine its reliability when solving this type of problems. The specimens are subjected to biaxial opening/compression loading; both results (numerical and experimental) are compared in order to evaluate the condition of directional stability on crack propagation. Finally, an apparent transition point related to the length of specimens was identified, in which the behaviour of values of SIF changes for different loading ratios.

  14. 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

  15. The role of biaxial stresses in discriminating between meaningful and illusory composite failure theories

    Science.gov (United States)

    Hart-Smith, L. J.

    1992-01-01

    The irrelevance of most composite failure criteria to conventional fiber-polymer composites is claimed to have remained undetected primarily because the experiments that can either validate or disprove them are difficult to perform. Uniaxial tests are considered inherently incapable of validating or refuting any composite failure theory because so much of the total load is carried by the fibers aligned in the direction of the load. The Ten-Percent Rule, a simple rule-of-mixtures analysis method, is said to work well only because of this phenomenon. It is stated that failure criteria can be verified for fibrous composites only by biaxial tests, with orthogonal in-plane stresses of the same as well as different signs, because these particular states of combined stress reveal substantial differences between the predictions of laminate strength made by various theories. Three scientifically plausible failure models for fibrous composites are compared, and it is shown that only the in-plane shear test (orthogonal tension and compression) is capable of distinguishing between them. This is because most theories are 'calibrated' against the measured uniaxial tension and compression tests and any cross-plied laminate tests dominated by those same states of stress must inevitably 'confirm' the theory.

  16. Direct Observation of the Biaxial Stress Effect on Efficiency Droop in GaN-based Light-emitting Diode under Electrical Injection

    Science.gov (United States)

    Zheng, Jinjian; Li, Shuiqing; Chou, Chilun; Lin, Wei; Xun, Feilin; Guo, Fei; Zheng, Tongchang; Li, Shuping; Kang, Junyong

    2015-12-01

    Light-emitting diode (LED) efficiency has attracted considerable interest because of the extended use of solid-state lighting. Owing to lack of direct measurement, identification of the reasons for efficiency droop has been restricted. A direct measurement technique is developed in this work for characterization of biaxial stress in GaN-based blue LEDs under electrical injection. The Raman shift of the GaN E2 mode evidently decreases by 4.4?cm?1 as the driving current on GaN-based LEDs increases to 700?mA. Biaxial compressive stress is released initially and biaxial tensile stress builds up as the current increases with respect to the value of stress-free GaN. First-principles calculations reveal that electron accumulation is responsible for the stress variation in InxGa1?xN/GaN quantum wells, and then reduces the transition probability among quantum levels. This behavior is consistent with the measured current-dependent external quantum efficiency. The rule of biaxial stress-dependent efficiency is further validated by controlling the biaxial stress of GaN-based LEDs with different sapphire substrate thicknesses. This work provides a method for direct observation of the biaxial stress effect on efficiency droop in LEDs under electrical injection.

  17. Investiagation on the finite fatigue strength of materials subjected to biaxial stress as a result of changing temperatures

    International Nuclear Information System (INIS)

    Design specifications for pressure vessels permit the yield point to be exceeded considerably in the case of secondary stress. Pressure components must therefore often be designed for finite fatigue strength. Dimensioning in accordance with the ASME code has hitherto been based on the results of uniaxial mechanical tests at constant temperature, using high safety factors. The author's own tests intend determine to what extent real loads are covered by thermal cycles in a biaxial stress field. At the same time, the limits of use of these materials under complex loads are determined. Therefore, in this research program biaxial cyclic tests were carried out on disks of unalloyed and austenitic materials. Lifetime was determined in dependence of the prevented deformations. The temperature cycles are between a low limiting temperature of 500C and a higher one of 3000C, 4000C or 5000C. (orig./RW) 891 RW/orig.- 892 RKD

  18. Experimental verification of the effect of biaxial state of stress on the fracture-mechanical characteristics of WWER pressure vessel materials - a research programme

    International Nuclear Information System (INIS)

    Previous experiments have shown that biaxial stress has an adverse effect on fracture toughness - under biaxial strain, fracture toughness may be some 40 % less than under uniaxial strain (ie., that found in standard tests using compact tension or three point bending). Under operating conditions, in the cylindrical part of a pressure vessel the stress is always biaxial; therefore, an experimental programme to check the effect of biaxial stress on reactor pressure vessel materials is proposed. The goal of the programme is defined, the current knowledge is summed up, and requirements on test specimens and test apparatus are set. The actual apparatus is described in some detail, and the method of test results evaluation is suggested. (A.K.) 2 figs., 1 ref

  19. Development and validation of an experimental procedure for studying the biaxial stress corrosion. Application to the systems: alloy-600/air and 316L/MgCl2

    International Nuclear Information System (INIS)

    One of the main preoccupation for maintaining EdF's nuclear pressurised water reactors is intergranular stress corrosion cracking of steam generator tubing (alloy 600: NC 15Fe). The most affected areas (first row U-bend and roll transition zone) are in biaxial stress state. The crack propagation is often axial and sometimes circumferential. The actual life prediction criterion for these structures depends on the maximal principal stress. The purpose of this study is to determine whether it is safe to use such a criterion in a case of biaxial stress state. A procedure is proposed and experimentally validated for designing specimen in a controlled biaxial stress state when submitted to traction. Quadrants I an IV of the stress space are the only ones explored. The aim is to use these specimens in order to realize stress corrosion tests in primary water with alloy 600. The procedure involves studying the biaxial behavior of the material. This shows the effect of hardening on the shape of the yield stress surface. The hardening of alloy 600 is mainly kinematic. The yield stress surface becomes concave in the hardening stress direction and flat in the opposite direction. The geometry of the specimen stems from parameterized shape optimisation. An elasto-viscoplastic behavior law is identified for alloy 600. Use of the law for calculating the strain state of one specimen is experimentally validated. This entire procedure has been successfully validated with biaxial stress corrosion cracking tests, using 316L and MgCl2 boiling at 154 deg C. In this case it is difficult to determine a life time criterion. It is shown that the criterion of the maximal principal stress is invalid in case of a biaxial stress state. (author)

  20. Quantification and significance of fluid shear stress field in biaxial cell stretching device

    OpenAIRE

    Thompson, MS; Abercrombie, SR; Ott, CE; Bieler, FH; Duda, GN; Ventikos, Y.

    2011-01-01

    A widely used commercially available system for the investigation of mechanosensitivity applies a biaxial strain field to cells cultured on a compliant silicone substrate membrane stretched over a central post. As well as intended substrate strain, this device also provides a fluid flow environment for the cultured cells. In order to interpret the relevance of experiments using this device to the in vivo and clinical situation, it is essential to characterise both substrate and fluid environm...

  1. Effect of grain shape and texture on equi-biaxial creep of stress relieved and recrystallized Zircaloy-4

    International Nuclear Information System (INIS)

    Zirconium alloys are extensively used in various types of fission reactors both light and heavy water types for different applications, examples being thin-walled tubing to clad radioactive fuel, grids, channels in boiling water reactors (BWRs) as well as pressure and calandria tubes in pressurized heavy water reactors (PHWRs). Biaxial creep behaviors of stress relieved and recrystallized thin-walled tubing of Zircaloy-4 are considered under equal hoop and axial stresses by internal pressurization superimposed with axial load. Both hoop and axial strains were monitored and the ratio of the strain rates along the hoop to axial directions is considered to represent the degree of anisotropy. The slightly stronger hoop direction of the recrystallized material became weaker compared to the axial direction following cold work and a stress-relief anneal. Crystallographic texture was considered in terms of x-ray pole figures from which the crystallite orientation distribution functions (CODF) were derived. A crystal plasticity model based on slip on representative systems was combined with the CODF to predict the creep anisotropy. It was found that the textural differences between the recrystallized and stress-relieved material is believed to invoke anisotropic grain boundary sliding leading to stress enhancement in the hoop direction. This stress enhancement is shown to account for the observed differences in creep behavior between the present equiaxed and columnar grain structures

  2. Biaxial stress relaxation of semilunar heart valve leaflets during simulated collagen catabolism: Effects of collagenase concentration and equibiaxial strain state.

    Science.gov (United States)

    Huang, Siyao; Huang, Hsiao-Ying Shadow

    2015-10-01

    Heart valve leaflet collagen turnover and remodeling are innate to physiological homeostasis; valvular interstitial cells routinely catabolize damaged collagen and affect repair. Moreover, evidence indicates that leaflets can adapt to altered physiological (e.g. pregnancy) and pathological (e.g. hypertension) mechanical load states, tuning collagen structure and composition to changes in pressure and flow. However, while valvular interstitial cell-secreted matrix metalloproteinases are considered the primary effectors of collagen catabolism, the mechanisms by which damaged collagen fibers are selectively degraded remain unclear. Growing evidence suggests that the collagen fiber strain state plays a key role, with the strain-dependent configuration of the collagen molecules either masking or presenting proteolytic sites, thereby protecting or accelerating collagen proteolysis. In this study, the effects of equibiaxial strain state on collagen catabolism were investigated in porcine aortic valve and pulmonary valve tissues. Bacterial collagenase (0.2 and 0.5?mg/mL) was utilized to simulate endogenous matrix metalloproteinases, and biaxial stress relaxation and biochemical collagen concentration served as functional and compositional measures of collagen catabolism, respectively. At a collagenase concentration of 0.5?mg/mL, increasing the equibiaxial strain imposed during stress relaxation (0%, 37.5%, and 50%) yielded significantly lower median collagen concentrations in the aortic valve (p?=?0.0231) and pulmonary valve (p?=?0.0183), suggesting that relatively large strain magnitudes may enhance collagen catabolism. Collagen concentration decreases were paralleled by trends of accelerated normalized stress relaxation rate with equibiaxial strain in aortic valve tissues. Collectively, these in vitro results indicate that biaxial strain state is capable of affecting the susceptibility of valvular collagens to catabolism, providing a basis for further investigation of how such phenomena may manifest at different strain magnitudes or in vivo. PMID:26405097

  3. Design of a cruciform bend specimen for determination of out-of- plane biaxial tensile stress effects on fracture toughness for shallow cracks

    International Nuclear Information System (INIS)

    Pressurized-thermal-shock loading in a reactor pressure vessel 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. A testing program is described that seeks to determine the effects of out-of-plane biaxial tensile loading on fracture toughness of RPV steels. A cruciform bend specimen that meets specified criteria for the testing pregam 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

  4. 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.

  5. Tuning the Exciton Binding Energies in Single Self-Assembled InGaAs/GaAs Quantum Dots by Piezoelectric-Induced Biaxial Stress:

    OpenAIRE

    Ding, F.; Singh, R.; Plumhof, J.D.; Zander, T; K?ápek, V.; Chen, Y. H.; Benyoucef, M.; Zwiller, V.; Dörr, K.; Bester, G.; Rastelli, A.; O. G. Schmidt (COVER PAGE)

    2010-01-01

    We study the effect of an external biaxial stress on the light emission of single InGaAs/GaAs(001) quantum dots placed onto piezoelectric actuators. With increasing compression, the emission blueshifts and the binding energies of the positive trion (X+) and biexciton (XX) relative to the neutral exciton (X) show a monotonic increase. This phenomenon is mainly ascribed to changes in electron and hole localization and it provides a robust method to achieve color coincidence in the emission of X...

  6. Some remarks on the inelastic behaviour of high temperature materials under biaxial stress state

    International Nuclear Information System (INIS)

    The purpose of the paper is to examine the validity of several inelastic constitutive models, which are expected to describe the plasticity-creep interaction behaviour of high temperature materials under multiaxial stress state. A constitutive equation in the framework of excess stress is developed, and calculated responses by use of the theories are compared with experimental results for SUS-304 and 2 1/4 Cr-1Mo steels under combined tension and torsion at high temperature levels. Some remarks on the inelastic behaviours are also stated, especially on the hardening phonomena under the plasticity-creep interaction and the rate dependence on the stress-strain relations. (orig./RF)

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

    Science.gov (United States)

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

    2016-01-01

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

  8. Tuning the exciton binding energies in single self-assembled InGaAs/GaAs quantum dots by piezoelectric-induced biaxial stress.

    Science.gov (United States)

    Ding, F; Singh, R; Plumhof, J D; Zander, T; Krápek, V; Chen, Y H; Benyoucef, M; Zwiller, V; Dörr, K; Bester, G; Rastelli, A; Schmidt, O G

    2010-02-12

    We study the effect of an external biaxial stress on the light emission of single InGaAs/GaAs(001) quantum dots placed onto piezoelectric actuators. With increasing compression, the emission blueshifts and the binding energies of the positive trion (X+) and biexciton (XX) relative to the neutral exciton (X) show a monotonic increase. This phenomenon is mainly ascribed to changes in electron and hole localization and it provides a robust method to achieve color coincidence in the emission of X and XX, which is a prerequisite for the possible generation of entangled photon pairs via the recently proposed "time reordering" scheme. PMID:20366855

  9. 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

  10. 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.)

  11. Biaxial model for bounding creep ratchetting 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

  12. Biaxial fatigue of metals the present understanding

    CERN Document Server

    Schijve, Jaap

    2016-01-01

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

  13. Biaxial vasoactivity of porcine coronary artery

    OpenAIRE

    Huo, Yunlong; Cheng, Yana; Zhao, Xuefeng; Lu, Xiao; Kassab, Ghassan S.

    2012-01-01

    The passive mechanical properties of blood vessel mainly stem from the interaction of collagen and elastin fibers, but vessel constriction is attributed to smooth muscle cell (SMC) contraction. Although the passive properties of coronary arteries have been well characterized, the active biaxial stress-strain relationship is not known. Here, we carry out biaxial (inflation and axial extension) mechanical tests in right coronary arteries that provide the active coronary stress-strain relationsh...

  14. Analytical modeling of the effect of crack depth, specimen size, and biaxial stress on the fracture toughness of reactor vessel steels

    International Nuclear Information System (INIS)

    Fracture, toughness values for A533-B reactor pressure vessel (RPV) steel obtained from test programs at Oak Ridge National Laboratory (ORNL) and University of Kansas (KU) are interpreted using the J-A2 analytical model. The analytical model is based on the critical stress concept and takes into consideration the constraint effect using the second parameter A2 in addition to the generally accepted first parameter J which represents the loading level. It is demonstrated that with the constraint level included in the model effects of crack depth (shallow vs deep), specimen size (small vs. large), and loading type (uniaxial vs biaxial) on the fracture toughness from the test programs can be interpreted and predicted

  15. Biaxial stretching of polyethylene, (2)

    International Nuclear Information System (INIS)

    The mechanism of oriented crystallization in mutually perpendicular direction to each other was investigated on the crosslinked linear polyethylene stretched successively and biaxially above melting point of raw material. To investigate the mechanism, the shrinkage stress, the degree of polarization and DSC of the film at the fixed length were measured on the crystallization process. The behavior observed on crystallization could be divided into that in the first period and that in the second period. The first period showed the domain of highly oriented crystallization of the crosslinked molecular chain, and in the second period the fold type crystals grew with highly oriented crystals in the first period as nuclear. Therefore, the formation of bi-component crystal structure is supposed for the crystallization. The biaxially oriented crystallization proceeded as follows: the uniaxial orientation to MD was observed in the first stretching in the initial stage, and then the further processing by the second stretching at a right angle caused the fold type crystallization of molecular chain oriented to TD. The film stretched fully and biaxially could be considered to have the oriented crystalline structure in which highly oriented fibril crystals and fold type crystals distribute at random. (auth.)

  16. Biaxial compression test technique

    Science.gov (United States)

    Hansard, E. T.

    1975-01-01

    Fixture and technique have been developed for predicting behavior of stiffened skin panels under biaxial compressive loading. Tester can load test panel independently in longitudinal and transverse directions. Data can also be obtained in combined mode.

  17. A Biaxial Fatigue Specimen for Uniaxial Loading

    OpenAIRE

    Bellett, Daniel; Morel, Franck; Morel, Anne; Lebrun, Jean-Lou

    2011-01-01

    The aim of this paper is to present a novel un-notched fatigue test specimen in which a biaxial stress state is achieved using a uniaxial loading condition. This allows the problem of multi-axial fatigue to be studied using relatively common one-axis servo-hydraulic testing machines. In addition the specimen presented here is very compact and can be made using a small volume of material (100x40x4.5mm). For this specimen, the degree of biaxiality, defined by the parameter is equal to approxima...

  18. 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.

  19. 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

  20. Biaxial dynamic testing of nuclear containment steel

    International Nuclear Information System (INIS)

    A test program has been initiated at the laboratories of the European Union Joint Research Centre of Ispra to investigate combined effects of high strain rates and biaxial stresses. The purpose is to assess the material behavior up to rupture in the special conditions which are produced during an explosion inside a nuclear metal containment. In the paper the main features of the campaign are discussed. (author). 19 refs., 4 figs

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

    International Nuclear Information System (INIS)

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

  2. Biaxial fatigue behavior of a powder metallurgical TRIP steel

    Directory of Open Access Journals (Sweden)

    S. Ackermann

    2015-10-01

    Full Text Available Multiaxial fatigue behavior is an important topic in critical structural components. In the present study the biaxial-planar fatigue behavior of a powder metallurgical TRIP steel (Transformation Induced Plasticity was studied by taking into account martensitic phase transformation and crack growth behavior. Biaxial cyclic deformation tests were carried out on a servo hydraulic biaxial tension-compression test rig using cruciform specimens. Different states of strain were studied by varying the strain ratio between the axial strain amplitudes in the range of -1 (shear loading to 1 (equibiaxial loading. The investigated loading conditions were proportional due to fixed directions of principal strains. The studied TRIP steel exhibits martensitic phase transformation from ?-austenite via ?-martensite into ?‘- martensite which causes pronounced cyclic hardening. The ?‘-martensite formation increased with increasing plastic strain amplitude. Shear loading promoted martensite formation and caused the highest ?‘-martensite volume fractions at fatigue failure in comparison to uniaxial and other biaxial states of strain. Moreover, the fatigue lives of shear tests were higher than those of uniaxial and other biaxial tests. The von Mises equivalent strain hypothesis was found to be appropriate for uniaxial and biaxial fatigue, but too conservative for shear fatigue, according to literature for torsional fatigue. The COD strain amplitude which is based on crack opening displacement gave a better correlation of the investigated fatigue lives, especially those for shear loading. Different types of major cracks were observed on the sample surfaces after biaxial cyclic deformation by using electron monitoring in an electron beam universal system and scanning electron microscopy (SEM. Specimens with strain ratios of 1, 0.5, -0.1 and -0.5 showed mode I major cracks (perpendicular to the axis of maximum principal strain. Major cracks after shear fatigue had partially mode II orientation (tilted 45° to the loading axes and afterwards bifurcated into two pairs of mode I cracks. Another shear test revealed a major crack of mode I orientation (parallel to the loading axes. These results are in good agreement to the literature. Micro cracks after shear fatigue were longer than those after biaxial fatigue with strain ratios of 1 and 0.5. Major and minor cracks after equibiaxial and shear loading showed crack branching and crack coalescence. The results on fatigue crack behavior support the assumption that the period of stage I (mode II crack propagation is much longer under shear loading than under other biaxial conditions due to absence of tensile stress normal to the planes of maximum shear strain under shear loading

  3. 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

  4. Lattice diffusion and surface segregation of B during growth of SiGe heterostructures by molecular beam epitaxy: effect of Ge concentration and biaxial stress

    CERN Document Server

    Portavoce, A; Christensen, J S; Gas, P; Ronda, A; ccsd-00002812, ccsd

    2004-01-01

    Si1-xGex/Si1-yGey/Si(100) heterostructures grown by Molecular Beam Epitaxy (MBE) were used in order to study B surface segregation during growth and B lattice diffusion. Ge concentration and stress effects were separated. Analysis of B segregation during growth shows that: i) for layers in epitaxy on (100)Si), B segregation decreases with increasing Ge concentration, i.e. with increased compressive stress, ii) for unstressed layers, B segregation increases with Ge concentration, iii) at constant Ge concentration, B segregation increases for layers in tension and decreases for layers in compression. The contrasting behaviors observed as a function of Ge concentration in compressively stressed and unstressed layers can be explained by an increase of the equilibrium segregation driving force induced by Ge additions and an increase of near-surface diffusion in compressively stressed layers. Analysis of lattice diffusion shows that: i) in unstressed layers, B lattice diffusion coefficient decreases with increasing...

  5. Lattice diffusion and surface segregation of B during growth of SiGe heterostructures by molecular beam epitaxy: effect of Ge concentration and biaxial stress.

    OpenAIRE

    Portavoce, A.; Gas, P.; Berbezier, I; Ronda, A.; Christensen, J.S.; Svensson, B.

    2004-01-01

    Si1-xGex/Si1-yGey/Si(100) heterostructures grown by Molecular Beam Epitaxy (MBE) were used in order to study B surface segregation during growth and B lattice diffusion. Ge concentration and stress effects were separated. Analysis of B segregation during growth shows that: i) for layers in epitaxy on (100)Si), B segregation decreases with increasing Ge concentration, i.e. with increased compressive stress, ii) for unstressed layers, B segregation increases with Ge concentrat...

  6. Biaxiality of chiral liquid crystals

    International Nuclear Information System (INIS)

    Using extended deGennes-Ginzburg-Landau free energy expansion in terms of the anisotropic part of the dielectric tensor field Q??(?) a connection between the phase biaxiality and the stability of various chiral liquid crystalline phases is studied. In particular the cholesteric phase, the cubic Blue Phases and the phases characterized by an icosahedral space group symmetry are analysed in detail. Also a general question concerning the applicability of the mean-field approximation in describing the chiral phases is addressed. By an extensive study of the model over a wide range of the parameters a new class of phenomena, not present in the original deGennes-Ginzburg-Landau model, has been found. These include: a) re-entrant phase transitions between the cholesteric and the cubic blue phases and b) the existence of distinct phases of the same symmetry but of different biaxialities. The phase biaxiality serves here as an extra scalar order parameter. Furthermore, it has been shown that due to the presence of the competing bulk terms in the free energy, the stable phases may acquire a large degree of biaxiality, also in liquid crystalline materials composed of effectively uniaxial molecules. A study of icosahedral space group symmetries gives a partial answer to the question as to whether an icosahedral quasicrystalline liquid could be stabilized in liquid crystals. Although, in general, the stability of icosahedral structures could be enhanced by the extra terms in the free energy no absolutely stable icosahedral phase has been found. (author). 16 refs, 3 figs, 1 tab

  7. Biaxial creep of zircaloy: Texture and temperature effects

    International Nuclear Information System (INIS)

    Zircaloy is commonly used as a cladding material for nuclear fuel elements. The cladding is subject to time-varying multiaxial stresses in service and the ability to accurately predict cladding behavior is necessary to maintain fuel integrity. This work investigates the biaxial creep behavior of recrystallized zircaloy at three temperatures and with four different crystallographic textures. In addition to measuring the creep behavior, the crystallographic texture is used to independently predict the creep behavior. 48 refs

  8. 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)

  9. 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.

  10. 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.

  11. Investigation of the Leak Response of a Carbon-Fiber Laminate Loaded in Biaxial Tension

    Science.gov (United States)

    Jackson, Wade C.; Ratcliffe, James G.

    2013-01-01

    Designers of pressurized structures have been reluctant to use composite materials because of concerns over leakage. Biaxial stress states are expected to be the worst-case loading condition for allowing leakage to occur through microcracks. To investigate the leakage behavior under in-plane biaxial loading, a cruciform composite specimen was designed that would have a relatively large test section with a uniform 1:1 biaxial loading ratio. A 7.6-cm-square test section was desired for future investigations of the leakage response as a result of impact damage. Many iterations of the cruciform specimen were evaluated using finite element analysis to reduce stress concentrations and maximize the size of the uniform biaxial strain field. The final design allowed the specimen to go to relatively high biaxial strain levels without incurring damage away from the test section. The specimen was designed and manufactured using carbon/epoxy fabric with a four-ply-thick, quasi-isotropic, central test section. Initial validation and testing were performed on a specimen without impact damage. The specimen was tested to maximum biaxial strains of approximately 4500micro epsilon without apparent damage. A leak measurement system containing a pressurized cavity was clamped to the test section and used to measure the flow rate through the specimen. The leakage behavior of the specimen was investigated for pressure differences up to 172 kPa

  12. Design of Bioprosthetic Aortic Valves using biaxial test data.

    Science.gov (United States)

    Dabiri, Y; Paulson, K; Tyberg, J; Ronsky, J; Ali, I; Di Martino, E; Narine, K

    2015-08-01

    Bioprosthetic Aortic Valves (BAVs) do not have the serious limitations of mechanical aortic valves in terms of thrombosis. However, the lifetime of BAVs is too short, often requiring repeated surgeries. The lifetime of BAVs might be improved by using computer simulations of the structural behavior of the leaflets. The goal of this study was to develop a numerical model applicable to the optimization of durability of BAVs. The constitutive equations were derived using biaxial tensile tests. Using a Fung model, stress and strain data were computed from biaxial test data. SolidWorks was used to develop the geometry of the leaflets, and ABAQUS finite element software package was used for finite element calculations. Results showed the model is consistent with experimental observations. Reaction forces computed by the model corresponded with experimental measurements when the biaxial test was simulated. As well, the location of maximum stresses corresponded to the locations of frequent tearing of BAV leaflets. Results suggest that BAV design can be optimized with respect to durability. PMID:26737002

  13. Biaxially Stretched Polycarbonate Film For Capacitors

    Science.gov (United States)

    Yen, Shaio-Ping S.; Lowry, Lynn E.; Bankston, Clyde P.

    1992-01-01

    Report describes experiments on effects of biaxial stretching on crystal structures, dielectric properties, and sellected thermal and mechanical properties of biaxially stretched polycarbonate films. Highest stretch ratios produce highest degree of crystallinity, with single crystalline phase and distribution of crystallites more nearly isotropic than uniaxially oriented film. Electrical properties at high temperatures improved.

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

    Science.gov (United States)

    Čopar, 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

  15. 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

  16. Field-Induced Rheology in Uniaxial and Biaxial Fields

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-06-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  20. Graphene flakes under controlled biaxial deformation

    Science.gov (United States)

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

    2015-12-01

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

  1. 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

  2. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-09-15

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

  4. 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

  5. In situ measurement of biaxial modulus of Si anode for Li-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Sethuraman, V.A.; Chon, M.J.; Shimshak, M.; Van Winkle, N.; Guduru, P.R. [School of Engineering, Brown University, Providence, RI (United States)

    2010-11-15

    We report in situ measurement of biaxial moduli of a Si thin-film electrode as a function of its lithium concentration. During lithiation, biaxial compressive stress is induced in the Si film and it undergoes plastic flow. At any state-of-charge (SOC), a relatively small delithiation-relithiation sequence unloads and reloads the film elastically. From the stress and strain changes during a delithiation-relithiation cycle, the biaxial modulus of the film is calculated. Stress change is obtained by measuring the change in substrate curvature using a Multi-beam Optical Sensor; the elastic strain change is obtained from the change in SOC. By repeating these measurements at several different values of SOC, the biaxial modulus was seen to decrease from ca. 70 GPa for Li{sub 0.32}Si to ca. 35 GPa for Li{sub 3.0}Si. Such a significant reduction in elastic modulus has important implications for modeling stress evolution and mechanical degradation in Si-based anodes. (author)

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

    KAUST Repository

    Pancheri, Francesco Q.

    2014-03-01

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

  7. 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.

  8. Biaxial extension of knitted steel fibre fabrics

    Science.gov (United States)

    Vanclooster, K.; Eshghyar, A.; Lomov, S. V.

    2011-05-01

    In this paper knitted steel fibre fabrics will be tested in biaxial extension. An in-house developed biaxial extension machine is used to apply a variety of strain conditions, which allows investigating the coupling between the wale and course direction of the fabrics and the degree of anisotropy in the fabric. Prior to testing a pretension level, to compensate the slack nature of the fabric, is determined by using a laser-measuring device. The strain inside the fabric is measured using a CCD camera technique. The results show the non-linear behaviour of the fabric and the coupling between the wale and the course direction. This will lead to a test protocol that can be used to evaluate the biaxial response of different types of knitted fabrics.

  9. Bulk and surface biaxiality in nematic liquid crystals

    CERN Document Server

    Biscari, P; Turzi, S; Biscari, Paolo; Napoli, Gaetano; Turzi, Stefano

    2006-01-01

    Nematic liquid crystals possess three different phases: isotropic, uniaxial, and biaxial. The ground state of most nematics is either isotropic or uniaxial, depending on the external temperature. Nevertheless, biaxial domains have been frequently identified, especially close to defects or external surfaces. In this paper we show that any spatially-varying director pattern may be a source of biaxiality. We prove that biaxiality arises naturally whenever the symmetric tensor $\\Sb=(\\grad \

  10. Topology Optimization of Stressed Capacitive RF MEMS Switches

    DEFF Research Database (Denmark)

    Philippine, Mandy A.; Sigmund, Ole; Rebeiz, Gabriel M.; Kenny, Thomas W.

    2013-01-01

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

  11. Anisotropic yield surfaces in bi-axial cyclic plasticity

    International Nuclear Information System (INIS)

    Some aspects of the behaviour of yield surfaces and work-hardening surfaces occurring in biaxial cyclic plasticity have been studied experimentally and theoretically. The experimental work consisted of subjecting thin-walled tubular steel specimens to cyclic plastic torsion in the presence of sustained axial loads of various magnitudes. The experimental results show that considerable anisotropy is induced when the cyclic shear strains are dominant. Although the true shapes of yield and work-hardening surfaces can be very complex, a mathematical model is presented which includes both anisotropy and Bauschinger effects. The model is able to qualitatively predict the deformation patterns during a cycle of applied plastic shear strain for a range of sustained axial stresses and also indicate the material response to changes in axial stress. (orig.)

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

    Science.gov (United States)

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

    2015-04-01

    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.

  13. Experimental and analytical comparison of constraint effects due to biaxial loading and shallow-flaws

    Energy Technology Data Exchange (ETDEWEB)

    Theiss, T.J.; Bass, B.R.; Bryson, J.W.

    1993-12-31

    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. The focus of studies described herein is on the evaluation of a micromechanical scaling model based on critical stressed volumes for quantifying crack-tip constraint through applications to experimental 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. Shallow-crack effects and far-field tensile out-of-plane biaxial loading have been identified as constraint issues that influence both fracture toughness and the extent of the toughness scatter band. Results from applications indicate that 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. Crack-tip constraint analyses of the shallow-crack cruciform specimen based on near-tip stress fields. Crack-tip constraint analyses of the shallow-crack cruciform specimen subjected to uniaxial or biaxial loading conditions are shown to represent a significant challenge for these methodologies. Unresolved issued identified from these analyses require resolution as part of a validation process for biaxial loading applications.

  14. Experimental and analytical comparison of constraint effects due to biaxial loading and shallow-flaws

    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. The focus of studies described herein is on the evaluation of a micromechanical scaling model based on critical stressed volumes for quantifying crack-tip constraint through applications to experimental 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. Shallow-crack effects and far-field tensile out-of-plane biaxial loading have been identified as constraint issues that influence both fracture toughness and the extent of the toughness scatter band. Results from applications indicate that 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. Crack-tip constraint analyses of the shallow-crack cruciform specimen based on near-tip stress fields. Crack-tip constraint analyses of the shallow-crack cruciform specimen subjected to uniaxial or biaxial loading conditions are shown to represent a significant challenge for these methodologies. Unresolved issued identified from these analyses require resolution as part of a validation process for biaxial loading applications

  15. Towards the biaxial nematic phase via specific intermolecular interactions

    International Nuclear Information System (INIS)

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

  16. Engineering piezoresistivity using biaxially strained silicon

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Richter, Jacob; Brandbyge, Mads; Thomsen, Erik Vilain; Hansen, Ole

    2008-01-01

    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...

  17. Biaxial crystal-based optical tweezers

    DEFF Research Database (Denmark)

    Angelsky, Oleg V.; Maksimyak, Andrew P.; Maksimyak, Peter P.; Hanson, Steen Grüner

    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...

  18. Biaxial torus around nematic point defects.

    Science.gov (United States)

    Kralj, S; Virga, E G; Zumer, S

    1999-08-01

    We study the biaxial structure of both line and point defects in a nematic liquid crystal confined within a capillary tube whose lateral boundary enforces homeotropic anchoring. According to Landau-de Gennes theory the local order in the material is described by a second-order tensor Q, which encompasses both uniaxial and biaxial states. Our study is both analytical and numerical. We show that the core of a line defect with topological charge M=1 is uniaxial in the axial direction. At the lateral boundary, the uniaxial ordering along the radial direction is reached in two qualitatively different ways, depending on the sign of the order parameter on the axis. The point defects with charge M=+/-1 exhibit a uniaxial ring in the plane orthogonal to the cylinder axis. This ring is in turn surrounded by a torus on which the degree of biaxiality attains its maximum. The typical lengths that characterize the structure of these defects depend both on the cylinder radius and the biaxial correlation length. It seems that the core of the point defect does not depend on the far nematic director field in the bulk limit. PMID:11969973

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

    Indian Academy of Sciences (India)

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

    2010-02-01

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

  20. Ferroelectricity in low-symmetry biaxial nematic liquid crystals

    International Nuclear Information System (INIS)

    Order parameters and phenomenological theory for both high- and low-symmetry biaxial nematic phases are presented and it is predicted that the chiral low-symmetry biaxial phase must be ferroelectric. This conclusion is based on general symmetry arguments and on the results of the Landau-de Gennes theory. The microscopic mechanism of the ferroelectric ordering in this chiral biaxial phase is illustrated using a simple molecular model based on dispersion interactions between biaxial molecules of low symmetry. Similar to the chiral smectic C* phase, the ferroelectricity in the chiral biaxial nematic phase is improper, i.e., polarization is not a primary order parameter and is not determined by dipolar interactions. Ferroelectric ordering in biaxial nematics may be found, in principle, in materials composed of chiral analogues of the tetrapod molecules which are known to exhibit biaxial phases. (fast track communication)

  1. 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.

  2. Performance testing of the Doorstopper biaxial strain cell

    Energy Technology Data Exchange (ETDEWEB)

    Stickney, R.G.; Senseny, P.E.; Hansen, F.D. (RE/SPEC, Inc., Rapid City, SD (USA))

    1983-11-01

    A laboratory testing program was conducted to evaluate the performance of the Council for Scientific and Industrial Research (CSIR) Doorstopper'' biaxial strain cell. This work was conducted in support of the Basalt Waste Isolation Project's in situ stress measurement program to be carried out within the reference repository horizon. Performance tests were designed to (1) select an adhesive suitable for installation of the Doorstopper, (2) evaluate the component parts of the Doorstopper, and (3) test the performance of the Doorstopper and selected adhesive. Test conditions were selected to simulate those expected at the reference repository horizon during overcoring (temperatures ranging from 40{degree}C to 65{degree}C with a humidity of up to 100 percent). 10 refs.

  3. Biaxial testing of nanoscale films on compliant substrates: Fatigue and fracture

    Science.gov (United States)

    Alaca, B. Erdem; Selby, John C.; Saif, M. T. A.; Sehitoglu, Huseyin

    2002-08-01

    Two problems of technological importance for microelectromechanical systems (MEMS) and microelectronics industry are addressed: fatigue of thin films and nanoscale film cracking. A device is described that can (1) conduct biaxial fatigue tests on thin films and (2) be utilized to study fracture patterns in nanoscale coatings under biaxial stress state. Thin-film specimens, in the form of circular membranes, are exposed to cyclic pressures between two fixed pressure limits. Corresponding pressure and specimen deflection are measured. Experimental results, including hysteresis loops spanning deflections of 15-50 ?m are presented for 4.6-?m-thick polyimide films. Furthermore, the evolution of crack patterns in a 150-nm-thick Al film deposited on a polyimide substrate is studied. Critical mode I stress intensity factor for Al is extracted from experimental results.

  4. Tunable uniaxial vs biaxial in-plane strain using compliant substrates

    Science.gov (United States)

    Yin, Haizhou; Peterson, R. L.; Hobart, K. D.; Shieh, S. R.; Duffy, T. S.; Sturm, J. C.

    2005-08-01

    In this letter, the relaxation of strained rectangular islands on compliant substrates is used to achieve semiconductor thin films with either uniaxial stress or uniaxial strain in the plane of the film over an area of tens of microns. The work is demonstrated using silicon and silicon-germanium alloy single-crystal thin films, with uniaxial strain values approaching 1%. The biaxially strained SiGe or SiGe /Si films on borophosphorosilicate glass (BPSG) were fabricated by a wafer bonding and layer transfer process. When the viscosity of BPSG drops at high temperatures for short times, films patterned in a rectangular shape can move laterally to relieve stress only in one in-plane direction. Thus one can tailor the strain from biaxial to uniaxial in the thin films.

  5. 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.

  6. Derivation of the Bi-axial Bending, Compression and Shear Strengths of Timber Beams:

    OpenAIRE

    Put, T. A. C. M.

    2012-01-01

    The derivation is given of the combined bi-axial bending, compression and shear strength of timber beams. As for other materials the elastic–full plastic limit design approach applies, which is known to precisely explain and predict uniaxial bending strength behaviour. The derivation is based on choosing the location of the neutral line. This provides the stress distribution in the beam cross section in the ultimate state for that case, making it possible to calculate the associated ultima...

  7. 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.

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

    Science.gov (United States)

    Kirkpatrick, Steven Wayne

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

  9. Topology Optimization of Stressed Capacitive RF MEMS Switches

    DEFF Research Database (Denmark)

    Philippine, Mandy A.; Sigmund, Ole; Rebeiz, Gabriel M.; Kenny, Thomas W.

    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 behav...

  10. Deformation behavior of micro-indentation defects under uniaxial and biaxial loads

    Science.gov (United States)

    Ma, Zhichao; Zhao, Hongwei; Lu, Shuai; Li, Hailian; Liu, Changyi; Liu, Xianhua

    2015-09-01

    The microdefects of structure frequently act as the source to generate initial cracks and lead to the fracture failure. Study on the deformation behaviors of embedded defects would be conducive to better understand the failure mechanisms of structural materials. Micro-indentation technique was applied to prepare the initial indentations as embedded surface defects at the gauge length section and central section of a cross-shaped AZ31B magnesium alloy specimen. A novel in situ biaxial tensile device was developed to apply the synchronous biaxial loads. Via the observation by an optical microscope with three-dimensional imaging and measurement functions, the changing laws of the indentation topographies under uniaxial and biaxial tensile loads were discussed. Compared with the gauge length section, the increasing trend of the indentation length of the central section was relatively flat, and the decreasing trend of the indentation depth was more significant. The changes of indentation topographies were explained by the Poisson effect, and the significant plastic tensile stress has led to the releasing of the residual stress around the indentation location and also promoted the planarization of the pileup.

  11. 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

  12. Biaxial nematic order induced by smectic fluctuations.

    Science.gov (United States)

    Zhang, C; Chakraborty, S; Ostapenko, T; Sprunt, S; Jákli, A; Gleeson, J T

    2012-08-01

    We report on a series of measurements on the microscopic structure and the magneto-optical properties of a calamitic liquid crystalline compound in its nematic phase. Structural studies show the existence of short-range, tilted smectic order consistent with pretransitional effects above an underlying smectic phase. Concomitantly, magneto-optical results exhibit the existence of an optic axis not collinear with the uniaxial director. This apparent biaxial nature is discussed within the context of coupling between the tensor nematic and the smectic order parameters. PMID:23005714

  13. 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.

  14. 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 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 (75mm by 2m by 2m) 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 plate tests and describes the analysis work undertaken to interpret the experiments satisfactorily. ((orig.))

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

    DEFF Research Database (Denmark)

    Løvdal, Alexandra Liv Vest; Andreasen, Jens Wenzel; Mikkelsen, Lars Pilgaard; Agersted, Karsten; Almdal, Kristoffer

    2016-01-01

    ) biaxial strain process, the mechanical properties of biaxial strained tubes can be further improved. This study investigated these properties in relation to their morphology and crystal orientation. Both processes yield the same mechanical strength and modulus, yet exhibit different crystal orientation...

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

    International Nuclear Information System (INIS)

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

  17. 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.

  18. 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.)

  19. 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

  20. Biaxial testing for nuclear grade graphite by ball on three balls assessment

    International Nuclear Information System (INIS)

    Nuclear grade (high-purity) graphite for fuel element and moderator material in Advanced Gas Cooling Reactors (AGR) displays large scatter in strength and a non-linear stress-strain response from the damage accumulation. These responses can be characterized as quasi-brittle behaviour. Current assessments of fracture in core graphite components are based on the linear elastic approximation and thus represent a major assumption. The quasi-brittle behaviour gives challenge to assess the real nuclear graphite component. The selected test method would help to bridge the gap between microscale to macro-scale in real reactor component. The small scale tests presented here can contribute some statistical data to manifests the failure in real component. The evaluation and choice of different solution design of biaxial test will be discussed in this paper. The ball on-three ball test method was used for assessment test follows by numerous of analytical method. The results shown that biaxial strength of the EY9 grade graphite depends on the method used for evaluation. Some of the analytical methods use to calculate biaxial strength were found not to be valid and therefore should not be used to assess the mechanical properties of nuclear graphite. (author)

  1. 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

  2. Stretching silicon: A uniaxial and biaxial strain generation process and the resulting mobility enhancement in silicon-on-insulator MOSFETs

    Science.gov (United States)

    Peterson, Rebecca Lorenz

    Strained silicon is of technological interest for its ability to increase charge carrier mobilities in MOSFETs and thereby improve circuit performance without requiring device scaling. At high vertical electric fields, biaxial tensile strain enhances electron mobility while uniaxial compressive strain enhances hole mobility, for example. In the present work, a process is developed to integrate upon a single wafer, for the first time, uniaxially-strained, biaxially-strained and unstrained silicon islands. The ultra-thin ( crystal direction. The strain generation method works by lateral expansion of a silicon/silicon germanium bi-layer island on a viscous borophosphorosilicate glass (BPSG) layer during high temperature (> 700°C) anneal. By manipulating the island geometry from squares to narrow rectangles, biaxial and uniaxial silicon strains are achieved. Numerical simulations of the lateral expansion process for islands of various aspect ratios identify process windows and island geometry requirements for maximum uniaxial strain. The modeled and measured strain results agree well. An undesired buckling process can roughen the film surface during anneals; the buckling and lateral expansion processes compete to determine the final state of the film. The amplitude of buckling can be reduced and its time scale lengthened by thinning the compliant BPSG layer. Differences in 1-D and 2-D buckling on uniaxially- and biaxially-stressed SiGe islands, respectively, are measured, and by comparison to models, attributed to the different magnitudes of 1-D and 2-D stress present in the films. Fully-depleted strained-SOI MOSFETs are fabricated using this strain generation process. By adding a silicon nitride barrier layer below the BPSG, device performance is greatly improved. Biaxial tensile strain of 0.38-0.52% enhances electron and hole mobilities by 30-55%. Comparable uniaxial tension parallel to a or channel improves electron mobilities by up to 72% and hole mobilities by up to 54%.

  3. Fatigue of concrete subjected to biaxial loading in the tension region

    Science.gov (United States)

    Subramaniam, Kolluru V. L.

    Rigid airport pavement structures are subjected to repeated high-amplitude loads resulting from passing aircraft. The resulting stress-state in the concrete is a biaxial combination of compression and tension. It is of interest to model the response of plain concrete to such loading conditions and develop accurate fatigue-based material models for implementation in mechanistic pavement design procedures. The objective of this work is to characterize the quasi-static and low-cycle fatigue response of concrete subjected to biaxial stresses in the tensile-compression-tension (t-C-T) region, where the principal tensile stress is larger in magnitude than the principal compressive stress. An experimental investigation of material behavior in the biaxial t-C-T region is conducted. The experimental setup consists of the following test configurations: (a) notched concrete beams tested in three-point bend configuration, and (b) hollow concrete cylinders subjected to torsion with or without superimposed axial tensile force. The damage imparted to the material is examined using mechanical measurements and an independent nondestructive evaluation (NDE) technique based on vibration measurements. The failure of concrete in t-C-T region is shown to be a local phenomenon under quasi-static and fatigue loading, wherein the specimen fails owing to a single crack. The crack propagation is studied using the principles of fracture mechanics. It is shown that the crack propagation resulting from the t-C-T loading can be predicted using mode I fracture parameters. It is observed that crack growth in constant amplitude fatigue loading is a two-phase process: a deceleration phase followed by an acceleration stage. The quasi-static load envelope is shown to predict the crack length at fatigue failure. A fracture-based fatigue failure criterion is proposed, wherein the fatigue failure can be predicted using the critical mode I stress intensity factor. A material model for the damage evolution during fatigue loading of concrete in terms of crack propagation is proposed. The crack growth acceleration stage is shown to follow Paris law. The model parameters obtained from uniaxial fatigue tests are shown to be sufficient for predicting the considered biaxial fatigue response.

  4. Dopant Diffusion under Pressure and Stress

    OpenAIRE

    Aziz, Michael

    2003-01-01

    The effects of stress on equilibrium point defect populations and on dopant diffusion in strained semiconductors are reviewed. The thermodynamic relationships presented permit the direct comparison of hydrostatic and biaxial stress experiments and of atomistic calculations of defect volumetrics for any proposed mechanism. Experiments on the effects of pressure and stress on the diffusivity of B and Sb are reviewed. The opposite effects of hydrostatic compression and of biaxial compression ...

  5. 52Cr Spinor Condensate: A Biaxial or Uniaxial Spin Nematic

    International Nuclear Information System (INIS)

    We show that the newly discovered 52Cr Bose condensate in zero magnetic field can be a spin nematic of the following kind: a 'maximum' polar state, a 'colinear' polar state, or a biaxial nematic ferromagnetic state. We also present the phase diagram with a magnetic field in the interaction subspace containing the chromium condensate. It contains many uniaxial and biaxial spin nematic phases, which often but not always break time reversal symmetry, and can exist with or without spontaneous magnetization

  6. 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

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

    Science.gov (United States)

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

    2015-07-01

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

  8. Biaxial alignment in sputter deposited thin films

    International Nuclear Information System (INIS)

    Biaxially aligned thin films have not only a preferential crystallographic out-of-plane orientation, but also have an alignment along a certain reference direction parallel to the substrate plane. This type of film has been obtained by unbalanced reactive magnetron sputter deposition on both amorphous glass and randomly textured polycrystalline substrates tilted with respect to the incoming material flux. First, we focus on the development of microstructure and crystallographic out-of-plane orientation. The results are summarized in an extended structure zone model. Based on experimental results, a mechanism for the in-plane alignment is proposed which shows that an in-plane alignment can only be obtained when an overgrowth mechanism drives the microstructural evolution of the thin film. The quality of the in-plane alignment can be evaluated from X-ray diffraction pole figures. The influence of several deposition parameters (target-substrate distance, target-substrate angle, deposition pressure, and substrate bias) on the degree of in-plane alignment is discussed. The influence of these parameters can be traced to the influence of two main properties, i.e. the mobility of the adatoms at the growing surface and the angular spread of the incoming material flux. Finally, since impurities are hard to exclude during deposition, their influence on the microstructure, the preferential out-of-plane orientation, and the in-plane alignment is reported

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yanfen, E-mail: yanfen.zhou@mydit.ie [Centre for Elastomer Research, Focas Research Institute, Dublin Institute of Technology, Dublin 8 (Ireland); Jerrams, Stephen [Centre for Elastomer Research, Focas Research Institute, Dublin Institute of Technology, Dublin 8 (Ireland); Betts, Anthony [Applied Electrochemistry Group, Focas Research Institute, Dublin Institute of Technology, Dublin 8 (Ireland); Chen, Lin [Beijing Aeronautical Science and Technology Research Institute, Commercial Aircraft Corporation of China (China)

    2014-08-01

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

  10. Stress state in perforated plates

    International Nuclear Information System (INIS)

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

  11. Magneto-optical technique for detecting the biaxial nematic phase.

    Science.gov (United States)

    Ostapenko, T; Zhang, C; Sprunt, S N; Jákli, A; Gleeson, J T

    2011-08-01

    The existence of the elusive biaxial phase has been the subject of much discussion since it was predicted by Freiser in 1970. More recently, there have been numerous attempts to find a thermotropic liquid crystal that exhibits a biaxial phase and with this, conflicting reports about whether such a phase has been positively identified in bent-core liquid crystals. One reason for the discrepancy is that there is currently no way to rule out surface effects or anchoring transitions, both of which may give a false positive identification of a uniaxial-biaxial nematic transition. We have developed a technique that uses a magnetic field to align the uniaxial director, thus widening its application to any bent-core nematic material. PMID:21929003

  12. Depletion-induced biaxial nematic states of boardlike particles

    International Nuclear Information System (INIS)

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

  13. 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.

  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. Bi-axial fracture strength characteristic of an ultra-thin flash memory chip

    International Nuclear Information System (INIS)

    Recently, ultra-thin chips with thicknesses of under 35 µm have emerged as an option for thinner, high performance electronic devices. For reliable electronic devices and high throughput packaging processes, the mechanical properties of ultra-thin chips need to be accurately understood. In this study, the fracture strength of an ultra-thin flash memory chip was measured using a ball-on-ring (BOR) test. To evaluate and validate the bi-axial strength in the BOR test, a finite element analysis was performed. It was compared with the analytical solution based on Hertzian contact theory. Flash memory chip specimens with different thicknesses were prepared and their bi-axial strengths were tested with respect to various wafer thinning process parameters such as grinding speed and polishing time. Raman spectroscopy was used to characterize the residual stress generated during the wafer thinning process. The surface roughness of the silicon wafer was measured using an atomic force microscope under various wafer thinning conditions. From the study, the fracture strength characteristics of the ultra-thin chip could be established as a function of the wafer thinning parameters. (paper)

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

    International Nuclear Information System (INIS)

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

  17. Soft elasticity in biaxial smectic and smectic-C elastomers

    CERN Document Server

    Stenull, O; Stenull, Olaf

    2006-01-01

    Ideal (monodomain) smectic-$A$ elastomers crosslinked in the smectic-$A$ phase are simply uniaxial rubbers, provided deformations are small. From these materials smectic-$C$ elastomers are produced by a cooling through the smectic-$A$ to smectic-$C$ phase transition. At least in principle, biaxial smectic elastomers could also be produced via cooling from the smectic-$A$ to a biaxial smectic phase. These phase transitions, respectively from $D_{\\infty h}$ to $C_{2h}$ and from $D_{\\infty h}$ to $D_{2h}$ symmetry, spontaneously break the rotational symmetry in the smectic planes. We study the above transitions and the elasticity of the smectic-$C$ and biaxial phases in three different but related models: Landau-like phenomenological models as functions of the Cauchy--Saint-Laurent strain tensor for both the biaxial and the smectic-$C$ phases and a detailed model, including contributions from the elastic network, smectic layer compression, and smectic-$C$ tilt for the smectic-$C$ phase as a function of both stra...

  18. 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.

  19. 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.

  20. Specimens and Reusable Fixturing for Testing Advanced Aeropropulsion Materials Under In-Plane Biaxial Loading. Part 1; Results of Conceptual Design Study

    Science.gov (United States)

    Ellis, J. R.; Sandlass, G. S.; Bayyari, M.

    2001-01-01

    A design study was undertaken to investigate the feasibility of using simple specimen designs and reusable fixturing for in-plane biaxial tests planned for advanced aeropropulsion materials. Materials of interest in this work include: advanced metallics, polymeric matrix composites, metal and intermetallic matrix composites, and ceramic matrix composites. Early experience with advanced metallics showed that the cruciform specimen design typically used in this type of testing was impractical for these materials, primarily because of concerns regarding complexity and cost. The objective of this research was to develop specimen designs, fixturing, and procedures which would allow in-plane biaxial tests to be conducted on a wide range of aeropropulsion materials while at the same time keeping costs within acceptable limits. With this goal in mind. a conceptual design was developed centered on a specimen incorporating a relatively simple arrangement of slots and fingers for attachment and loading purposes. The ANSYS finite element code was used to demonstrate the feasibility of the approach and also to develop a number of optimized specimen designs. The same computer code was used to develop the reusable fixturing needed to position and grip the specimens in the load frame. The design adopted uses an assembly of slotted fingers which can be reconfigured as necessary to obtain optimum biaxial stress states in the specimen gage area. Most recently, prototype fixturing was manufactured and is being evaluated over a range of uniaxial and biaxial loading conditions.

  1. Processing-structure-property relationships in uni- and biaxially stretched binary and ternary blends

    Science.gov (United States)

    Zhou, Xixian

    Processing-structure-property relationships in uni and biaxially stretched PVDF/PMMA binary blends and PEN/PEI/PEEK ternary blends were investigated using a variety of characterization techniques that probe the structure at different levels. PVDF is a fast crystallizing polymer. It can form amorphous blends with PMMA which is fairly easy to process in their rubbery region. At the stretching temperature up to Tg + 10 ˜ 15sp°C, the blends with PVDF fraction more than 55 exhibit yielding due to the presence of the crystalline superstructure yet stress crystallizable films. The yielding and associated neck formation gradually disappear for the blends containing less than 55 wt%. The thickness uniformity and surface smoothness of the produced films are improved in these films upon stretching particularly when the influence of stress hardening is present. This causes self leveling in the films. At the lower stretch ratios (ca. lambdasbMD\\ ? 3x), 55/45 blend shows no crystallinity and crystalline orientation. Beyond this point, very highly oriented crystalline domains emerge. This is as a result of dilution effect at such compositions where the entanglement density of the PVDF chains is reduced thereby increasing efficiency of orientation that resembles crystallization from dilute solutions except in this case the solvent is the PMMA phase. Stretching converts the crystalline phase from alpha to beta in 85/15 and 70/30 wt% blends, while in 55/15 blend the crystalline regions are exclusively in beta form. A combination of four point diagrams with "lozenge" shape appears in SAXS patterns. A structure model has been proposed based on the three-phase morphology and SAXS theory. In this study, we concentrated on the biaxial stretching behavior of PEN rich and PEI rich crystallizable PEN/PEI/PEEK ternary blends. The main objective was to increase the glass transition temperature of the blends containing large fraction of PEN while maintaining strain induced crystallizability. This was not possible with PEN/PEI blends containing more than 30sp°% PEI. Addition of small amount (10-30%) of highly crystallizable PEEK were found to maintain strain crystallizabilities even in blends containing large fraction of PEI. Structural hierarchy developed in biaxially stretched blends was investigated. In PEN rich blends (containing 10% PEEK), low temperature highly oriented alpha modification PEN crystalline regions were found. In the blends containing large fraction of PEI, PEEK was found to crystallize upon stretching while PEN remained amorphous. These studies indicated that crystallizability of PEN that is lost by the addition of PEI beyond 33% can be recovered with the addition of PEEK. This allows one to produce uniform films with high glass transition temperature.

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

    CERN Document Server

    Fadeyeva, Tatyana; Anischenko, Pavel; Volyar, Alexander

    2011-01-01

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

  3. Biaxial fatigue properties of thin-walled composite tubes

    Science.gov (United States)

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

    1984-01-01

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

  4. Interaction diagrams of short columns under biaxial bending

    International Nuclear Information System (INIS)

    The use of design curves for uniaxial bending is favoured by engineers, be case of their numerous advantage over available numerical methods. For short columns subjected to biaxial bending, the engineers are forced to use approximate numerical methods accepted by the codes of practice. An attempt is made in this paper to expand a new technique developed by Najmi, (1986) and by Najami and Tay em (1993) for the design of such columns together with reliable design. charts which are paramount for efficient design By using the transformation sections at the ultimate load, the handling of the problem is then done through flexural formulae, which are more manageable than the equivalent equilibrium equations. Design curves for a typical cross section subject to different eccentricities are presented. The curves were purposely designed to render the uniaxial bending case as a special case of biaxial bending. (author). 8 refs., 10 figs

  5. Influences of the biaxial strain and c-screw dislocation on the clustering in InGaN alloys

    Science.gov (United States)

    Lei, Huaping; Chen, Jun; Ruterana, Pierre

    2010-11-01

    Using the molecular dynamics simulation based on Stillinger-Weber potentials, the roles of lattice mismatch and threading dislocations (c-screw type) on phase segregation in InGaN alloys have been explored. The thermodynamic stability and structural deformation of the InGaN alloys with In-rich clusters are analyzed when biaxial stress and c-screw dislocations act on the systems. The results show that the formation of In-rich clusters is suppressed in the case of lattice mismatch, whereas it takes place in the presence of c-screw dislocations independent of the strain condition of InGaN alloys.

  6. 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.

  7. Inhomogeneous configurations of magnetization of ferromagnetic films with biaxial anisotropy

    International Nuclear Information System (INIS)

    The system of the Landau-Lifshitz equations and magnetostatic equations for a ferromagnetic film with biaxial anisotropy and a Q-factor smaller than unity is reduced to a single scalar equation for the magnetostatic potential. Such a procedure is possible if the magnetization modulation scale in the sample considerably exceeds the characteristic magnetic length. The solutions to this equation describing inhomogeneous periodic magnetic configurations are obtained. The energy analysis of these configurations is carried out

  8. Biaxial deformation of collagen and elastin fibers in coronary adventitia

    OpenAIRE

    Chen, Huan; Slipchenko, Mikhail N.; LIU Yi; Zhao, Xuefeng; Cheng, Ji-Xin; Lanir, Yoram; Kassab, Ghassan S.

    2013-01-01

    The microstructural deformation-mechanical loading relation of the blood vessel wall is essential for understanding the overall mechanical behavior of vascular tissue in health and disease. We employed simultaneous mechanical loading-imaging to quantify in situ deformation of individual collagen and elastin fibers on unstained fresh porcine coronary adventitia under a combination of vessel inflation and axial extension loading. Specifically, the specimens were imaged under biaxial loads to st...

  9. 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

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

    Science.gov (United States)

    2015-01-01

    Efficient driving of piezoelectric materials is desirable when operating transducers for biomedical applications such as high intensity focused ultrasound (HIFU) or ultrasound imaging. More efficient operation reduces the electric power required to produce the desired bioeffect or contrast. Our preliminary work [Cole et al. Journal of Physics: Condensed Matter. 2014;26(13):135901.] suggested that driving transducers by applying orthogonal electric fields can significantly reduce the coercivity that opposes ferroelectric switching. We present here the experimental validation of this biaxial driving technique using piezoelectric ceramics typically used in HIFU. A set of narrow-band transducers was fabricated with two sets of electrodes placed in an orthogonal configuration (following the propagation and the lateral mode). The geometry of the ceramic was chosen to have a resonance frequency similar for the propagation and the lateral mode. The average (± s.d.) resonance frequency of the samples was 465.1 (± 1.5) kHz. Experiments were conducted in which each pair of electrodes was driven independently and measurements of effective acoustic power were obtained using the radiation force method. The efficiency (acoustic/electric power) of the biaxial driving method was compared to the results obtained when driving the ceramic using electrodes placed only in the pole direction. Our results indicate that the biaxial method increases efficiency from 50% to 125% relative to the using a single electric field. PMID:26418550

  11. Absence of rippling in graphene under biaxial tensile strain

    Science.gov (United States)

    Rakshit, Bipul; Mahadevan, Priya

    2010-10-01

    Recent experiments [C. H. Lui, L. Liu, K. F. Mak, G. W. Flynn, and T. F. Heinz, Nature (London) 462, 339 (2009)10.1038/nature08569] on graphene grown on ultraflat substrates have found no rippling in graphene when subject to temperature cycling. Unsupported/unstrained films of graphene as well as films grown on various substrates on the other hand have been found to show rippling effects. As graphene grown on a substrate is invariably strained, we examine the behavior of the out-of-plane acoustic-phonon mode with biaxial tensile strain. This mode is generally associated with the rippling of graphene. We find that it can be fit to a relation of the form w2=Ak4+Bk2 , where w and k are the frequency and wave vector, respectively. The coefficient A is found to show a weak dependence on strain while B is found to increase linearly with strain. The strain-induced hardening explains the absence of rippling in graphene subject to biaxial strain. In addition, we find that graphene when subject to a biaxial tensile strain is found to undergo a structural transition with the mode at K going soft at a strain percentage of 15%.

  12. 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...

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

    Science.gov (United States)

    D'Alessandro, Kacie Caple

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

  14. Global limit load solutions for plates with surface cracks under combined biaxial forces and cross-thickness bending

    International Nuclear Information System (INIS)

    Lower bound limit load solutions for surface cracks in plates under combined end force, cross-thickness bending moment and tensile/compressive membrane stress parallel to the crack are derived based on the von Mises yield criterion. From these solutions, particular limit loads for plates with extended surface cracks and through-thickness cracks or uncracked plates under the same loading conditions are obtained. The limit load solutions for surface cracks in plates under combined tension and bending due to Lei and Fox can be reproduced from the solutions in this paper by setting the stress parallel to the crack plane to zero. - Highlights: • Lower bound global limit load solution for rectangular surface cracks in plates. • Combined biaxial stress/force and cross-thickness bending moment. • Solutions based on lower bound limit load theorem and von Mises yield criterion. • Solutions valid for proportional/non-proportional loading

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    This paper addresses the elastic-plastic behavior of type 316 stainless steel, one of the major structural alloys used in liquid-metal fast breeder reactor components. The study was part of a continuing program to develop a structural design technology applicable to advanced reactor systems. Here, behaviour of solution annealed material was examined through biaxial stress experiments conducted at room temperature under radial loadings (?3tau=sigma) in tension-torsion stress space. The effects of both stress limited monotonic loading and strain limited cyclic loading were determined on the size, shape and position of yield loci corresponding to small offset strain (10 microstrain) definition of yield. In the present work, the aim was to determine the extent to which the constitutive laws previously recommended for type 304 stainless steel are applicable to type 316 stainless steel. It was concluded that for the conditions investigated, the inelastic behavior of the two materials are qualitatively similar. Specifically, the von Mises yield criterion provides a reasonable approximation of initial yield behavior and the subsequent hardening behavior, at least under small offset definitions of yield, is to the first order kinematic in nature. (Auth.)

  17. The Effect of Biaxial Strain and Layer Thickness on Octahedral Rotation in LaNiO3

    Science.gov (United States)

    McBride, Patrick; Janotti, Anderson; Dreyer, Cyrus; Himmetoglu, Burak; van de Walle, Chris

    2014-03-01

    Heterostructures of complex oxides have attracted great attention for the interplay between structure, electronic, and magnetic properties, offering unique opportunities in device applications. Here we investigate the effects of epitaxial strain and layer thickness on the structural properties of LaNiO3. We perform first-principles calculations based on density functional theory to investigate the NiO6 octahedral tilts and Ni-O bond lengths of biaxially stressed LaNiO3 layers in LaNiO3/SrTiO3 superlattices. Recent experimental results suggest that octahedral connectivity in these superlattices strongly influence the octahedral rotations in the LaNiO3 layer, and thus, determines its electronic behavior. In this talk we will present a quantitative analysis for the octahedral tilt angles as a function of both biaxial stress and distance from the substrate for LaNiO3 grown on SrTiO3 (001). Our results indicate that LaNiO3 exhibits vanishing octahedral tilt angles under certain strain conditions, a finding that holds important consequences for its electronic properties. Supported by the Bonderson Foundation and the National Energy Research Scientific Computing Center.

  18. STRESS

    Directory of Open Access Journals (Sweden)

    Suchitra D. Patankar

    2015-11-01

    Full Text Available Every person experience stress. Stress is the term which has become part of everybody’s life. It occur automatically in every human being but its level may be mild, moderate or high. During stress several physical and emotional changes takes place. It affect on cognitive functioning also. It can produce chronic physiological and psychological disorders. The present paper throws light on nature of stress, reactions to stress, effects of stress, stress management and techniques that are useful for stress reduction.

  19. 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.

  20. BEGA-a biaxial excitation Generator for automobiles

    DEFF Research Database (Denmark)

    Scridon, S.; Boldea, Ion; Tutelea, L.; Blaabjerg, Frede; Ritchie, Andrew Ewen

    2005-01-01

    This paper presents the design and test results for a biaxial excitation generator/motor for automobiles (BEGA), which has a three-phase stator and a salient-pole excited heteropolar rotor with multiple flux barriers filled with low-cost permanent magnets (PMs). For this new generator, the low......-voltage regulation is obtained by the flux-barrier PM combination with field (excitation) low-power control and a full-power diode rectifier in the stator. Good power/volume and superior efficiency (up to 80%) are obtained at costs comparable to those of an existing Lundell generator. The generator configuration...

  1. Uniaxial and Biaxial Spin Nematic Phases Induced by Quantum Fluctuations

    International Nuclear Information System (INIS)

    It is shown that zero point quantum fluctuations completely lift the accidental continuous degeneracy that is found in mean field analysis of quantum spin nematic phases of hyperfine spin-2 cold atoms. The result is two distinct ground states which have higher symmetries: a uniaxial spin nematic and a biaxial spin nematic with dihedral symmetry Dih4. There is a novel first-order quantum phase transition between the two phases as atomic scattering lengths are varied. We find that the ground state of 87Rb atoms should be a uniaxial spin nematic. We note that the energy barrier between the phases could be observable in dynamical experiments

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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)

  7. Stress

    Science.gov (United States)

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

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Zehui Jiang

    2012-11-01

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

  10. Stress

    Scientific Electronic Library Online (English)

    Abel Matos, Santos; João Jácome De, Castro.

    1998-12-01

    Full Text Available O presente artigo faz uma revisão histórica do Stress e define-o. Apresenta o Síndroma de Adaptação Geral (SAG), abordando os diversos aspectos biológicos, psicológicos e sociais, bem como os sintomas e sinais do Stress. Refere os aspectos psicossociais do Stress, as causas deste na pessoa, família [...] e sociedade. Descrevem-se as formas de medida e avaliação do Stress, a importância do Stress como agente não patológico e as suas consequências na saúde, focando os mecanismos de adaptação ao Stress. Abstract in english This article presents a historical view of Stress and its definition. The General Adaptation Syndrome (GAS) is described, focusing on the biological, psychological and social aspects of Stress, with their signs and symptoms. The psychosocial aspects of Stress are described, presenting the causes at [...] the personal, family and society. The ways of assessing Stress are presented, and its importance as a non pathological factor and its consequences in health, and discussing the ways of coping with Stress.

  11. Buckling of a stiff thin film on a compliant substrate under anisotropic biaxial prestrain

    Science.gov (United States)

    Ou, ZhiCheng; Yao, XiaoHu; Zhang, XiaoQing; Fan, XueJun

    2016-02-01

    The structure of stretchable electronics is based on the buckling of a thin film on a compliant substrate. Under anisotropic biaxial prestrains, this structure may buckle into several patterns, including cylindrical, checkerboard, and undulating patterns. The displacement and energy of each pattern are deduced analytically. By comparing their minimum potential energies, the critical buckling condition of each pattern is determined. After secondary bifurcation, the checkerboard pattern occurs just above the critical prestrains, but the undulating pattern dominates other regions. The buckling amplitude and wavenumber of the undulating pattern are shown under biaxial prestrains. Even if the structure is under equi-biaxial prestrains, it may buckle into an asymmetric undulating pattern.

  12. Thermotropic Uniaxial and Biaxial Nematic and Smectic Phases in Bent-Core Mesogens

    International Nuclear Information System (INIS)

    Two azo substituted achiral bent-core mesogens have been synthesized. Optical polarizing microscopy and synchrotron X-ray scattering studies of both compounds reveal the existence of the thermotropic uniaxial and biaxial nematic and three smectic phases at different temperatures in these single component small molecule systems. The transition from the uniaxial to biaxial nematic phase is confirmed to be second order. The transitions from the biaxial nematic to the underlying smectic phase and between the smectic phases have barely discernible heat capacity signatures and thus are also second order.

  13. Thermotropic Uniaxial and Biaxial Nematic and Smectic Phases in Bent-Core Mesogens

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Venna; Kang, Shin-Woong; Suresh, K.A.; Joshi, Leela; Wang, Qingbing; Kumar, Satyendra (Raman); (Kent); (CLCR)

    2010-07-20

    Two azo substituted achiral bent-core mesogens have been synthesized. Optical polarizing microscopy and synchrotron X-ray scattering studies of both compounds reveal the existence of the thermotropic uniaxial and biaxial nematic and three smectic phases at different temperatures in these single component small molecule systems. The transition from the uniaxial to biaxial nematic phase is confirmed to be second order. The transitions from the biaxial nematic to the underlying smectic phase and between the smectic phases have barely discernible heat capacity signatures and thus are also second order.

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

    Science.gov (United States)

    Martin, James E.

    2013-09-01

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

  15. On the electron mobility enhancement in biaxially strained Si MOSFETs

    Science.gov (United States)

    Driussi, F.; Esseni, D.; Selmi, L.; Hellström, P.-E.; Malm, G.; Ha?llstedt, J.; Östling, M.; Grasby, T. J.; Leadley, D. R.; Mescot, X.

    2008-04-01

    This paper reports a detailed experimental and simulation study of the electron mobility enhancement induced by the biaxial strain in (0 0 1) silicon MOSFETs. To this purpose, ad hoc test structures have been fabricated on strained Si films grown on different SiGe virtual substrates and the effective mobility of the electrons has been extracted. To interpret the experimental results, we performed simulations using numerical solutions of Schroedinger-Poisson equations to calculate the charge and the momentum relaxation time approximation to calculate the mobility. The mobility enhancement with respect to the unstrained Si device has been analyzed as a function of the Ge content of SiGe substrates and of the operation temperature.

  16. Stress.

    OpenAIRE

    Charlton, B G

    1992-01-01

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

  17. Effects of electric field and biaxial flexure on the failure of poled lead zirconate titanate.

    Science.gov (United States)

    Wang, Hong; Wereszczak, Andrew A

    2008-12-01

    Reliable design of lead zirconate titanate (PZT) piezo stack actuators demands that several issues, including electromechanical coupling and ceramic strength-size scaling, be scrutinized. This study addresses those through the use of ball-on-ring (BoR) biaxial flexure strength tests of a PZT piezoelectric material that is concurrently subjected to an electric field. The Weibull strength distributions and fracture surfaces were examined. The mechanical failures were further analyzed in terms of internal stress, energy release rate, and domain-switching toughening. Both the sign and the magnitude of an electric field had a significant effect on the strength of poled PZT within the tested range. A surface flaw type with an average depth of around 18 microm was identified to be the strength limiter and responsible for the failure of the tested PZT under both mechanical and electromechanical loadings. With a value of 0.74 MPa.m(1/2) in the absence of electric field, the fracture toughness of the poled PZT was affected by an applied electric field just as the strength was affected. These results and observations have the potential to serve probabilistic reliability analysis and design optimization of multilayer PZT piezo actuators. PMID:19126481

  18. Collective behaviour and spacing of necks in ductile plates subjected to dynamic biaxial loading

    Science.gov (United States)

    Zaera, R.; Rodríguez-Martínez, J. A.; Vadillo, G.; Fernández-Sáez, J.; Molinari, A.

    2015-12-01

    Diffuse or localized dynamic necking of a sheet metal is a major issue in high speed forming processes, leading to unacceptable thinning and even failure if fully developed, and in the dynamic behaviour of metallic structural elements of small thickness used for energy absorption purposes. This process is frequently related to the collective development of localization bands resulting in a necking pattern which depends on the sheet properties and on the loading conditions. This work investigates the spacing between necking bands in sheets made of a thermoviscoplastic metal and submitted to dynamic biaxial loading. For that task a linear perturbation technique, derived within a 2D framework which specifically accounts for stress triaxiality effects upon strain localization, has been developed. Using this methodology, a dominant instability mode can be identified, whose wavelength is related to the necking-band spacing. Likewise, fully 3D finite element simulations have been performed in order to verify and complement the outcomes of the aforementioned theoretical approach. The effects of loading conditions (loading path and loading rate), and thermal coupling on the stability of the deformation process and on the distance between necking bands are examined. We have shown that the neck spacing increases with the ratio of strains and decreases with the loading rate and the temperature rise.

  19. Layer-specific residual deformations and uniaxial and biaxial mechanical properties of thoracic porcine aorta.

    Science.gov (United States)

    Peña, Juan A; Martínez, Miguel A; Peña, Estefanía

    2015-10-01

    In this paper we hypothesize that the layer-separated residual stresses and mechanical properties of layer-separated thoracic aorta arteries may be dependent on arterial location of the vessel. To demonstrate any possible position differences, we measured the axial pre-stretch and opening angle and performed uniaxial and biaxial tests under physiological loads to study the mechanical behavior of both intact and layer-separated porcine aortic samples taken from thoracic region. In addition, we also provided constitutive parameters for each layer that can be used by biomedical engineers for investigating better therapies and developing artery-specific devices. We found that the opening angle for whole artery and adventitia layer are smaller and intima greater for proximal segments than for the distal thoracic ones. For the axial pre-stretch, our results showed significant increased values of the stretch ratios with location. We found that lower thoracic samples are stiffer than upper ones with the most important differences corresponding to those between the proximal and distal behaviors in the circumferential direction. The anisotropy represented by the different circumferential and longitudinal response is more remarkable in lower thoracic aorta. Finally, adventitia and intima samples present a tendency to be stiffer and more isotropic than the corresponding media samples in both directions for upper thoracic aorta and to be more anisotropic for lower thoracic aorta. PMID:26103440

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

    DEFF Research Database (Denmark)

    Larsen, Arne Nylandsted; Zangenberg, Nikolaj

    2005-01-01

    Results from diffusion studies of different impurities in biaxially strained Si and Si"1"-"xGe"x for low x-values will be presented. The structures are all molecular-beam epitaxy (MBE) grown on strain-relaxed Si"1"-"xGe"x layers, and the impurity profiles are introduced during growth. We have in particular been concerned with the effect of biaxial strain (compressive and tensile) on the diffusion of pure vacancy-assisted diffusers (Sb and, partly, Ge) and pure interstitial-assisted diffusers (B and P). It is found that compressive biaxial strain retards the diffusion of the interstitial-assisted diffusers, whereas tensile biaxial strain enhances the diffusion of these impurities. The opposite is the case for the vacancy-assisted diffusers.

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

    Science.gov (United States)

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

    2015-12-01

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

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

    Data.gov (United States)

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

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

    CERN Document Server

    Mackay, Tom G

    2013-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2011-10-01

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

  6. Stress

    DEFF Research Database (Denmark)

    Keller, Hanne Dauer

    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  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. Stress-rupture testing under superimposed steam corrosion

    International Nuclear Information System (INIS)

    Continuing long-time stress-rupture testing under biaxial stresses and superimposed steam corrosion of Incoloy Alloy 800 thin wall tubing, the extent and morphology of stress-assisted additional surface and bulk oxidation was evaluated by quantitative metallography. This paper describes the stress-assisted additional corrosion as function of tangential stress or corresponding rupture-life, creep strain, and creep rate. The results are presented and explained on the basis of surface and bulk penetrating oxide morphology. (orig.)

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-07-19

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

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

    OpenAIRE

    Djaziri, Soundes; Renault, Pierre-Olivier; Hild, François; Le Bourhis, Eric; Goudeau, Philippe; Thiaudière, Dominique; Faurie, Damien

    2011-01-01

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

  12. Preparation of biaxially oriented TlCu-1234 thin films

    CERN Document Server

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

    1999-01-01

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

  13. Inelastic response of metal matrix composites under biaxial loading

    Science.gov (United States)

    Lissenden, C. J.; Mirzadeh, F.; Pindera, M.-J.; Herakovich, C. T.

    1991-01-01

    Theoretical predictions and experimental results were obtained for inelastic response of unidirectional and angle ply composite tubes subjected to axial and torsional loading. The composite material consist of silicon carbide fibers in a titanium alloy matrix. This material is known to be susceptible to fiber matrix interfacial damage. A method to distinguish between matrix yielding and fiber matrix interfacial damage is suggested. Biaxial tests were conducted on the two different layup configurations using an MTS Axial/Torsional load frame with a PC based data acquisition system. The experimentally determined elastic moduli of the SiC/Ti system are compared with those predicted by a micromechanics model. The test results indicate that fiber matrix interfacial damage occurs at relatively low load levels and is a local phenomenon. The micromechanics model used is the method of cells originally proposed by Aboudi. Finite element models using the ABACUS finite element program were used to study end effects and fixture specimen interactions. The results to date have shown good correlation between theory and experiment for response prior to damage initiation.

  14. Equi-biaxial tension tests on magneto-rheological elastomers

    Science.gov (United States)

    Schubert, Gerlind; Harrison, Philip

    2016-01-01

    A bespoke test rig has been designed to facilitate testing of magneto-rheological (MR) elastomers (MREs) under equi-biaxial tension using a standard universal test machine. Tests were performed up to 10% strain on both isotropic and anisotropic MREs with and without the application of an external magnetic field. Assumptions regarding the material’s response were used to analyse stress–strain results in the two stretching directions. The assumptions have been verified previously by uniaxial tension tests and by simulations of the magnetic flux distribution performed using a commercial multi-physics finite element software. The MR effect, which is defined as the increase in tangent modulus at a given strain, has been studied versus engineering strain. The latter was measured optically in the experiments using a digital image correlation system. Relative MR effects up to 74% were found when the particle alignment of anisotropic MREs was oriented parallel to an applied magnetic induction of just 67.5 mT.

  15. Thermodynamics of Diffusion under Pressure and Stress: Relation to Point Defect Mechanisms

    OpenAIRE

    Aziz, Michael

    1997-01-01

    A thermodynamic formalism is developed for illuminating the predominant point defect mechanism of self- and impurity diffusion in silicon and is used to provide a rigorous basis for point defect-based interpretation of diffusion experiments in biaxially strained epitaxial layers in the Si–Ge system. A speci?c combination of the hydrostatic and biaxial stress dependences of the diffusivity is +/- 1 times the atomic volume, depending upon whether the predominant mechanism involves vacancies or...

  16. A new bi-axial cantilever beam design for biomechanics force measurements.

    Science.gov (United States)

    Lin, Huai-Ti; Trimmer, Barry A

    2012-08-31

    The demand for measuring forces exerted by animals during locomotion has increased dramatically as biomechanists strive to understand and implement biomechanical control strategies. In particular, multi-axial force transducers are often required to capture animal limb coordination patterns. Most existing force transducers employ strain gages arranged in a Wheatstone bridge on a cantilever beam. Bi-axial measurements require duplicating this arrangement in the transverse direction. In this paper, we reveal a method to embed a Wheatstone bridge inside another to allow bi-axial measurements without additional strain gages or additional second beams. This hybrid configuration resolves two force components from a single bridge circuit and simplifies fabrication for the simultaneous assessment of normal and transverse loads. This design can be implemented with two-dimensional fabrication techniques and can even be used to modify a common full bridge cantilever force transducer. As a demonstration of the new design, we built a simple beam which achieved bi-axial sensing capability that outperformed a conventional half-bridge-per-axis bi-axial strain gage design. We have used this design to measure the ground reaction forces of a crawling caterpillar and a caterpillar-mimicking soft robot. The simplicity and increased sensitivity of this method could facilitate bi-axial force measurements for experimental biologists. PMID:22776687

  17. Stress Effects on Defects and Dopant Diffusion in Si

    OpenAIRE

    Aziz, Michael

    2001-01-01

    The effects of stress on equilibrium point defect populations and on dopant diffusion for single crystals free of extended defects are reviewed. The thermodynamic relationships presented permit the direct comparison of hydrostatic and biaxial stress experiments and of atomistic calculations under hydrostatic and nonhydrostatic stress for any proposed mechanism. Experiments on the effects of pressure and stress on the diffusivity are reviewed. For Sb in Si, using as input the measured effect o...

  18. 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...

  19. Temperature dependence of refractive indices near uniaxial-biaxial nematic phase transition

    International Nuclear Information System (INIS)

    The uniaxial discotic (ND) and calamitic (NC) nematic phases are characterized by an order parameter which is a second-rank, symmetric, traceless tensor with two different eigenvalues and three in the biaxial nematic (NB) phase. The optical dielectric tensor may be chosen as the microscopic order parameter. The optical characterization of these uniaxial and biaxial nematic phases requires the measurements of two and three refractive indices, respectively. These optical parameters were determined near the reentrant isotropic (IRE)-ND-NB-NC-isotropic (I) phase transitions in a lyotropic mixture of potassium laurate, decanol and D2O. The dynamic of micellar configuration of the uniaxial and biaxial nematic phases is discussed as a consequence of our refractive index data

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

    Indian Academy of Sciences (India)

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

    2003-08-01

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

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

    Science.gov (United States)

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

    2015-02-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Rao,Y.; Greener, J.; Avila-Orta, C.; Hsiao, B.; Blanton, T.

    2008-01-01

    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.

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

    Science.gov (United States)

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

    2014-09-01

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

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

    International Nuclear Information System (INIS)

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

  5. 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

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

    International Nuclear Information System (INIS)

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

  7. Polarization features of acoustic spectra in uniaxial and biaxial nematic liquid crystals

    International Nuclear Information System (INIS)

    The results of investigation of uniaxial and biaxial nematic liquid crystals dynamics with molecules of the various forms are presented. These condensed matters possess internal spatial anisotropy and for their adequate description introduction of additional dynamic quantities is necessary. They are vectors of spatial anisotropy and conformational degrees of freedom. Investigation of dynamics of the given condensed matters is based on Hamiltonian formalism in which framework the nonlinear dynamic equations for uniaxial and biaxial nematic liquid crystals are derived. Spectra of collective excitations are obtained and their polarization features are investigated.

  8. Low-frequency green functions asymptotics in uniaxial and biaxial nematic liquid crystals

    International Nuclear Information System (INIS)

    Uniaxial and biaxial nematic liquid crystals are examples of the complicated condensed matters possessing an internal microstructure shown on macroscopic level in the form of a number of the physical phenomena and processes. In this work the dynamic behavior of the studied condensed matters in alternative external field is investigated. On the basis of the nonlinear dynamic equations with sources for uniaxial and biaxial nematics the general analytical expressions of low-frequency Green functions asymptotics are obtained and the analysis of their features in the region of small wave vectors and frequencies is carried out.

  9. 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.

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

    Science.gov (United States)

    Liu, Jianguang; Wang, Zhongjin; Meng, Qingyuan

    2012-04-01

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

  11. Biaxial creep deformation behavior of Fe–14Cr–15Ni–Ti modified austenitic stainless steel fuel cladding tube for sodium cooled fast reactor

    Energy Technology Data Exchange (ETDEWEB)

    Mathew, M.D., E-mail: mathew@igcar.gov.in [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamil Nadu (India); Ravi, S.; Vijayanand, V.D.; Latha, S. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamil Nadu (India); Dasgupta, Arup [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamil Nadu (India); Laha, K. [Mechanical Metallurgy Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamil Nadu (India)

    2014-08-15

    Highlights: • Significant amounts of creep strain is observed in the axial and hoop directions. • Hoop strain is much higher than the axial strain. • Steady state hoop rate is lower than steady state axial rate. • Steady state hoop rate is comparable with creep rate evaluated from uniaxial tests. • Alloy D9 exhibits anisotropy in creep deformation. - Abstract: Twenty percent cold worked Fe–14Cr–15Ni–Ti modified austenitic stainless steel is used as the cladding tube material for the fuel pins of the Prototype Fast Breeder Reactor in India. Biaxial creep properties of the tubes have been studied at 973 K by carrying out creep tests by internally pressurizing the tubes. Hoop and axial components of creep strain were measured and found to be significantly different. For a given gas pressure, steady state hoop rate was higher than the axial rate. Steady state hoop and axial creep rates followed Norton's power law with the same stress exponent n = 7. Steady state hoop rates determined from biaxial creep tests agreed with the steady state creep rates determined from uniaxial creep tests. For a thin walled closed tube under internal pressure, significant axial deformation along with hoop deformation is indicative of anisotropic deformation of the material.

  12. Creation of biaxial body center cubic tungsten nanorods under dynamic shadowing effect

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Liang, E-mail: chenl9@rpi.edu; Lu, Toh-Ming; Wang, Gwo-Ching

    2013-07-31

    Using a dynamic oblique angle deposition in a flipping rotation mode where the flux incident angle continuously changes during the magnetron sputter deposition, we demonstrated that a stable, biaxial (110)[11{sup ¯}0] body center cubic (alpha-phase) tungsten nanorod film can be grown on amorphous substrates. In contrast, we showed that only a fiber-textured, metastable A15 (beta-phase) tungsten nanorod film was obtained using the conventional rotation mode where the oblique incident flux angle was fixed with the substrate rotating around the surface normal. Different flipping rotation speeds were performed to study the effect of dynamic shadowing on texture axis angular dispersion. The sample grown at 0.3 rotations per minute was observed to have the minimum out-of-plane and in-plane orientation dispersions characterized by the reflection high energy electron diffraction surface pole figure technique. The biaxial texture selection under the flipping rotation mode is explained qualitatively. - Highlights: • Stable alpha-phase biaxial W nanorods were produced with dynamic flipping rotation. • Metastable beta-phase W nanorods were grown by stationary oblique angle deposition. • Biaxial stable W nanorods could be used as a buffer layer for semiconductors.

  13. The effect of zirconia thickness on the biaxial flexural strength of zirconiaceramic bilayered discs.

    Science.gov (United States)

    Sinmazisik, Gulden; Tarcin, Bilge; Demirbas, Bulent; Gulmez, Turgut; Bor, Emire; Ozer, Fusun

    2015-01-01

    The aim of this study was to assess the effect of zirconia core thickness on the biaxial flexural strength values of zirconia-porcelain bilayered discs. A total of 60 discs with 0.3, 0.4, and 0.5 mm thickness were obtained from a fully sintered zirconia block. A 1.5-mm thick layer of veneer porcelain was fired on the zirconia specimens and biaxial flexural strength tests were performed on the bilayered discs. In each group, the loading surface was the veneer porcelain in half of the specimens (core in tension) and the zirconia core surface in the other half (core in compression). The zirconia core thickness had no effect on the biaxial flexural strength of zirconiaporcelain bilayered discs when the core was in tension (p>0.05). Whereas, when the core was in compression, an increase in the zirconia core thickness resulted in an increase in the biaxial flexural strength (p<0.05). PMID:26438987

  14. On the isotropic-biaxial phase transition in nematic liquid crystals

    CERN Document Server

    Gaeta, Giuseppe

    2015-01-01

    We apply a recently developed technique to determine adapted coordinates for the sixth degree Landau-deGennes potential, in which the potential is specially simple, to analyze the possibility of a direct transition between the fully symmetric state and a biaxial phase in nematic liquid crystals. {Our results confirm, with simpler computations, results by Allender and Longa.

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

    DEFF Research Database (Denmark)

    Jönsson, Jeppe; Bondum, T. H.

    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...

  16. Creation of biaxial body center cubic tungsten nanorods under dynamic shadowing effect

    International Nuclear Information System (INIS)

    Using a dynamic oblique angle deposition in a flipping rotation mode where the flux incident angle continuously changes during the magnetron sputter deposition, we demonstrated that a stable, biaxial (110)[11¯0] body center cubic (alpha-phase) tungsten nanorod film can be grown on amorphous substrates. In contrast, we showed that only a fiber-textured, metastable A15 (beta-phase) tungsten nanorod film was obtained using the conventional rotation mode where the oblique incident flux angle was fixed with the substrate rotating around the surface normal. Different flipping rotation speeds were performed to study the effect of dynamic shadowing on texture axis angular dispersion. The sample grown at 0.3 rotations per minute was observed to have the minimum out-of-plane and in-plane orientation dispersions characterized by the reflection high energy electron diffraction surface pole figure technique. The biaxial texture selection under the flipping rotation mode is explained qualitatively. - Highlights: • Stable alpha-phase biaxial W nanorods were produced with dynamic flipping rotation. • Metastable beta-phase W nanorods were grown by stationary oblique angle deposition. • Biaxial stable W nanorods could be used as a buffer layer for semiconductors

  17. 2D nonlocal versus 3D bifurcation studies for biaxially loaded plates

    DEFF Research Database (Denmark)

    Benallal, A.; Tvergaard, Viggo

    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 ...

  18. Experimental investigation on rectangular reinforced concrete beam subjected to bi-axial shear and torsion

    Directory of Open Access Journals (Sweden)

    Chayanon Hansapinyo

    2003-01-01

    Full Text Available This paper presents the experimental investigation on the failure mechanism and ultimate capacity of rectangular reinforced concrete beam under combined action of bi-axial shear accompanied with torsion through the test of four reinforced concrete members. The simple experimental set-up for a simply-supported beam under one point loading is introduced in this study by applying eccentric load to the tilted beam. This requires only one hydraulic jack to produce the complicated bi-axial shear and torsional loading. The main parameter is the magnitude of torsion induced to specimens which is relatively represented by the torsion-to-shear ratio. In addition, the influence of torsion on ultimate capacity of reinforced concrete with different ratio of two shears is investigated. From the experimental results, it is found that the increase in the magnitude of torsion about 69 percent drastically decreases bi-axial shear capacity as much as 12 to 39 percent according to the ratio of bi-axial shears. The experimental results are compared with the capacities calculated by the available interaction formula between uni-axial shear and torsion in the current design codes. The comparison indicates that the current design codes give quite conservative values of ultimate capacity.

  19. Stability and internal stresses in Au(001)/Ni multilayers

    CERN Document Server

    Deutsch, T

    2003-01-01

    Defining the stability criteria for biaxially strained Ni, we show that the body-centred tetragonal (bct) Ni structure is not stable on an Au(001) substrate and changes to a face centred cubic (fcc) (110) structure with many stacking faults. Nevertheless, for a thin film, the bct Ni structure can be stabilized by the interface stresses. Using the stress at atomic level, the profile of the internal stresses is given as a function of Ni film thickness.

  20. Consistent stress-strain ductile fracture model as applied to two grades of beryllium

    International Nuclear Information System (INIS)

    Published yield and ultimate biaxial stress and strain data for two grades of beryllium are correlated with a more complete method of characterizing macroscopic strain at fracture initiation in ductile materials. Results are compared with those obtained from an exponential, mean stress dependent, model. Simple statistical methods are employed to illustrate the degree of correlation for each method with the experimental data

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

    International Nuclear Information System (INIS)

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

  2. Biaxiality-induced magnetic field effects in bent-core nematics: molecular-field and Landau theory.

    Science.gov (United States)

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

    2013-12-01

    Nematic liquid crystals composed of bent-core molecules exhibit unusual properties, including an enhanced Cotton-Mouton effect and an increasing isotropic (paranematic)-nematic phase transition temperature as a function of magnetic field. These systems are thought to be good candidate biaxial liquid crystals. Prompted by these experiments, we investigate theoretically the effect of molecular biaxiality on magnetic-field-induced phenomena for nematic liquid crystals, using both molecular field and Landau theory. The geometric mean approximation is used in order to specify the degree of molecular biaxiality using a single parameter. We reproduce experimental field-induced phenomena and predict also an experimentally accessible magnetic critical point. The Cotton-Mouton effect and temperature dependence of the paranematic-nematic phase transition are more pronounced with increased molecular biaxiality. We compare our theoretical approaches and make contact with recent relevant experimental results on bent-core molecular systems. PMID:24483467

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

    International Nuclear Information System (INIS)

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

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

    CERN Document Server

    Li Peng; Mazumder, J

    2003-01-01

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

  5. 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

  6. Biaxial stress-strain behavior of chemical and physical gels of poly(vinyl alcohol).

    Czech Academy of Sciences Publication Activity Database

    Meissner, Bohumil; Mat?jka, Libor

    2008-01-01

    Ro?. 49, ?. 10 (2008), s. 2560-2567. ISSN 0032-3861 R&D Projects: GA AV ?R IAA400500701 Institutional research plan: CEZ:AV0Z40500505 Keywords : poly(vinyl alcohol) gels * pure shear behavior * constitutive equation Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.331, year: 2008

  7. 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)

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

    International Nuclear Information System (INIS)

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

  9. Insertion Testing of Polyethylene Glycol Microneedle Array into Cultured Human Skin with Biaxial Tension

    Science.gov (United States)

    Takano, Naoki; Tachikawa, Hiroto; Miyano, Takaya; Nishiyabu, Kazuaki

    Aiming at the practical use of polyethylene glycol (PEG) microneedles for transdermal drug delivery system (DDS), a testing apparatus for their insertion into cultured human skin has been developed. To simulate the variety of conditions of human skin, biaxial tension can be applied to the cultured human skin. An adopted testing scheme to apply and control the biaxial tension is similar to the deep-draw forming technique. An attention was also paid to the short-time setup of small, thin and wet cultured skin. One dimensional array with four needles was inserted and influence of tension was discussed. It was found that tension, deflection of skin during insertion and original curvature of skin are the important parameters for microneedles array design.

  10. The Generation of Biaxial Optical Anisotropies in Polyimide Films by an Uniaxial Stretch Method

    Science.gov (United States)

    King, Jinn?Shing; Whang, Wha?Tzong; Lee, Wen?Chin; Chang, Li?Ming

    2006-05-01

    A new biaxial-retardation film prepared from the uniaxial-stretched polyimide (PI) film was developed for compensating the viewing angle of liquid-crystal displays. A new aliphatic PI showing high transparence and low glass-transition temperature was firstly prepared for the biaxial-retardation film purpose. Both retardations in x-y and x-z planes of PI films were highly increased after stretching them uniaxially at 260 °C. Good uniformity of birefringence in well-stretched PI films was observed visually with two crossed polarizers. The birefringence variations of nx-ny (difference of refractive indexes between x- and y-axes) and nx-nz during the stretching process were highly affected by PI structure.

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

    Science.gov (United States)

    Kim, Munho; Mi, Hongyi; Cho, Minkyu; Seo, Jung-Hun; Zhou, Weidong; Gong, Shaoqin; Ma, Zhenqiang

    2015-05-01

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

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-25

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

  14. The nuts and bolts of supersymmetric gauge theories on biaxially squashed three-spheres

    CERN Document Server

    Martelli, Dario

    2011-01-01

    We present the gravity dual to a class of three-dimensional N=2 supersymmetric gauge theories on a biaxially squashed three-sphere, with a non-trivial background gauge field. This is described by a 1/2 BPS Euclidean solution of four-dimensional N=2 gauged supergravity, consisting of a Taub-NUT-AdS metric with a non-trivial instanton for the graviphoton field. The holographic free energy of this solution agrees precisely with the large N limit of the free energy obtained from the localized partition function of a class of Chern-Simons quiver gauge theories. We also discuss a different supersymmetric solution, whose boundary is a biaxially squashed Lens space S^3/Z_2 with a topologically non-trivial background gauge field. This metric is of Eguchi-Hanson-AdS type, although it is not Einstein, and has a single unit of gauge field flux through the S^2 cycle.

  15. Hyperfine fields in ZnO studied under uni- and biaxial pressure

    International Nuclear Information System (INIS)

    The II-VI semiconductor ZnO has many potential applications in optoelectronic and sensor devices. When used as a transparent conducting contact it is often grown epitaxially onto a different substrate with the consequence that the layers are biaxially strained due to lattice mismatch. Similarly, impurity-implanted layers can lead to the development of local strain fields. Strain usually changes the electronic properties of layers and/ or implanted crystal regions. Detailed knowledge about local strain and its influence on the crystal fields is therefore helpful in predicting changes in crystal properties. The perturbed angular correlation technique was applied to study the electric field gradient (EFG) at the site of implanted In dopants in ZnO under uniaxial and biaxial strain. The observed linear change of the EFG with pressure and a change in symmetry due to compression perpendicular to the c-axis could be well reproduced by theoretical calculations using the point charge model.

  16. 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.

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

    Science.gov (United States)

    Goto, Masanao; Takezoe, Hideo; Ishikawa, Ken

    2010-02-01

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

  18. Synthesis and vibrating properties ZnSe/Ge bi-axial heterostructural nanowires

    Science.gov (United States)

    Xu, Xiaofeng; Wang, Chunrui; Liu, Jian; Cai, Junshen; Chen, Xiaoshuang

    2011-01-01

    Single-crystalline ZnSe/Ge bi-axial heterostructural nanowires were grown via a simple one-step thermal evaporation of mixed ZnSe and Ge powders. The heterostructure nanowires have uniform diameter of 200 nm and their length ranges are from several tens to several hundreds of micrometers. Both the zinc-blende ZnSe and diamond-like cubic Ge sub-nanowires in the heterostructures are single crystalline, and grow along the [1 1 1] direction. The sub-nanowires of ZnSe and Ge, with ideal interfaces along the growth orientation, have diameters of 120 and 80 nm, respectively. The experimental evidence suggests that the bi-axial nanowires are formed via a co-growth mechanism. The vibrating property of the nanowire was investigated by Raman spectroscopy at room-temperature.

  19. Hyperfine fields in ZnO studied under uni- and biaxial pressure

    Energy Technology Data Exchange (ETDEWEB)

    Przewodnik, R.; Kessler, P., E-mail: kessler@hiskp.uni-bonn.de; Vianden, R. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Germany)

    2013-05-15

    The II-VI semiconductor ZnO has many potential applications in optoelectronic and sensor devices. When used as a transparent conducting contact it is often grown epitaxially onto a different substrate with the consequence that the layers are biaxially strained due to lattice mismatch. Similarly, impurity-implanted layers can lead to the development of local strain fields. Strain usually changes the electronic properties of layers and/ or implanted crystal regions. Detailed knowledge about local strain and its influence on the crystal fields is therefore helpful in predicting changes in crystal properties. The perturbed angular correlation technique was applied to study the electric field gradient (EFG) at the site of implanted In dopants in ZnO under uniaxial and biaxial strain. The observed linear change of the EFG with pressure and a change in symmetry due to compression perpendicular to the c-axis could be well reproduced by theoretical calculations using the point charge model.

  20. Hyperfine fields in ZnO studied under uni- and biaxial pressure

    Science.gov (United States)

    Przewodnik, R.; Kessler, P.; Vianden, R.

    2013-05-01

    The II-VI semiconductor ZnO has many potential applications in optoelectronic and sensor devices. When used as a transparent conducting contact it is often grown epitaxially onto a different substrate with the consequence that the layers are biaxially strained due to lattice mismatch. Similarly, impurity-implanted layers can lead to the development of local strain fields. Strain usually changes the electronic properties of layers and/ or implanted crystal regions. Detailed knowledge about local strain and its influence on the crystal fields is therefore helpful in predicting changes in crystal properties. The perturbed angular correlation technique was applied to study the electric field gradient (EFG) at the site of implanted In dopants in ZnO under uniaxial and biaxial strain. The observed linear change of the EFG with pressure and a change in symmetry due to compression perpendicular to the c-axis could be well reproduced by theoretical calculations using the point charge model.

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

    OpenAIRE

    Chillingworth, David

    2014-01-01

    We describe a general 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 {\\em et al.} (1986) in an influential paper in {\\em Liquid Crystals} {\\bf 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...

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

    OpenAIRE

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

    2012-01-01

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

  3. Raman spectroscopy of graphene and bilayer under biaxial strain: bubbles and balloons

    OpenAIRE

    Zabel, Jakob; Nair, Rahul R; Ott, Anna; Georgiou, Thanasis; Geim, Andre K.; Novoselov, Kostya S.; CASIRAGHI, cinzia

    2012-01-01

    In this letter we use graphene bubbles to study the Raman spectrum of graphene under biaxial (e.g. isotropic) strain. Our Gruneisen parameters are in excellent agreement with the theoretical values. Discrepancy in the previously reported values is attributed to the interaction of graphene with the substrate. Bilayer balloons (intentionally pressurized membranes) have been used to avoid the effect of the substrate and to study the dependence of strain on the inter-layer interactions.

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

    Science.gov (United States)

    Mandle, Richard J; Goodby, John W

    2016-02-01

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

  5. 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.

  6. 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

  7. On constitutive descriptors of the biaxial mechanical behaviour of human abdominal aorta and aneurysms

    OpenAIRE

    Ferruzzi, J.; Vorp, D. A.; Humphrey, J.D.

    2010-01-01

    The abdominal aorta (AA) in older individuals can develop an aneurysm, which is of increasing concern in our ageing population. The structural integrity of the ageing aortic wall, and hence aneurysm, depends primarily on effective elastin and multiple families of oriented collagen fibres. In this paper, we show that a structurally motivated phenomenological ‘four-fibre family’ constitutive relation captures the biaxial mechanical behaviour of both the human AA, from ages less than 30 to over ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Kakmeni, F.M. Moukam [Department of Physics, Faculty of Science, University of Buea, P.O. Box 63, Buea (Cameroon) and Abdus Salam International Centre for Theoretical Physics, P.O. Box 586 Strada Costiera, II-34014 Trieste (Italy)]. E-mail: fmoukam@uycdc.uninet.cm; Nguenang, J.P. [Departement de Physique, Faculte des Sciences, Universite de Douala, B.P. 24157 Douala (Cameroon) and Abdus Salam International Centre for Theoretical Physics, P.O. Box 586 Strada Costiera, II-34014 Trieste (Italy)]. E-mail: jpnguen@uycdc.uninet.cm; Kofane, T.C. [Laboratoire de Mecanique, Faculte des Sciences, Universite de Yaounde, B.P. 812 Yaounde (Cameroon) and Abdus Salam International Centre for Theoretical Physics, P.O. Box 586 Strada Costiera, II-34014 Trieste (Italy)]. E-mail: tkofane@uycdc.uninet.cm

    2006-11-15

    In this paper, we show that the bi-axial magnetic material modeled by Bloch equation admits chaotic solutions for certain set of numerical values assigned to the system 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 converges to zero.

  9. 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)

  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. Microstructure changes in poly(ethylene terephthalate) in thick specimens under complex biaxial loading

    OpenAIRE

    Marco, Yann; Chevalier, Luc

    2008-01-01

    We present an experimental investigation into the strain-induced crystalline microstructure, under biaxial elongation in Polyethylene terephthalate (PET). The aim of our study is to achieve both mechanical tests representative from the blow-moulding process, and micro- structural measurements. We therefore examine how the microstructure of a polymer subjected to a complex strain field evolves in terms of its crystalline ratio, its molecular orientation and the size of its crystallites. PET in...

  12. Air-coupled guided waves combined with thermography for monitoring fatigue in biaxially loaded composite tubes

    OpenAIRE

    Rheinfurth, M.; Schmidt, F.; Döring, D.; Solodov, I., Rahammer, M., Busse, G.; Busse, G.; Van der Horst, P.

    2011-01-01

    Non-destructive methodologies for remote monitoring of fatigue induced by mechanical load in fibre reinforced plastics are presented. Hollow cylinders (glass fibre winding) were stepwise biaxially fatigued and measured in single-sided access configurations. Based on conversion of air-coupled ultrasound to guided waves, it is shown that accumulated fatigue damage is accompanied by decrease in phase velocity and increase in attenuation. The change in wave velocity caused by fatigue is shown to ...

  13. 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.

  14. A strain device imposing dynamic and uniform equi-biaxial strain to cultured cells.

    Science.gov (United States)

    Sotoudeh, M; Jalali, S; Usami, S; Shyy, J Y; Chien, S

    1998-01-01

    The objective of this study is to design a new apparatus to allow the control of the magnitude and frequency of dynamic stretch applied uniformly to cells cultured on a silicon elastic membrane. The apparatus is designed to produce equi-biaxial dynamic stretches with area changes ranging from 0% to 55% and frequencies ranging from 0 to 2 Hz. Homogeneous finite strain analysis using triangles of markers was performed to compute the symmetric two-dimensional Lagrangian strain tensor on the membrane. Measurements of strain in both static and dynamic conditions showed that the shear component of the strain tensor (Erc) was near zero, and that there was no significant difference between radial (Err) and circumferential (Ecc) components, indicating the attainment of equi-biaxial strain. Bovine aortic endothelial cells were transiently transfected with a chimeric construct in which the luciferase reporter is driven by TPA-responsive elements (TRE). The transfected cells cultured on the membrane were stretched. The luciferase activity increased significantly only when the cells were stretched by 15% or more in area. Cells in different locations of the membrane showed similar induction of luciferase activities, confirming that strain is uniform and equi-biaxial across the membrane. PMID:9525759

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

    Science.gov (United States)

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

    2011-10-01

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

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

    OpenAIRE

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

    2002-01-01

    We present the results of a systematic study using the density functional theory (within the local density approximation) of the effects of biaxial strain and composition on the self-diffusion of Si and Ge in SiGe alloys diffusing by a vacancy mechanism. The biaxial strain dependence of the vacancy formation energy was reconfirmed with previous calculations. The effect of biaxial strain on the interaction potential energy between a substitutional Ge atom and a vacancy was ca...

  17. Stress management

    OpenAIRE

    Prof.Univ. Dr. Paul Marinescu

    2012-01-01

    ? ??????? ???????? ?????????? ?? ?? stress management ??? ???’ ???????? ?? ?? ???? ??? ??????????? ?? ?????? ?? ????? ??? ????????? ?????????? ????? (HRM), ?? ????? ???????? ????? ??? ??? ???????????? ??????? ???????????, ???? ???????? ??????????, ????? ??? ????? ?????????? ?????, ????????? stress ????? ???????????? ???? ??????????? / ???? ??????????. ???????????? ??? ??????? ???? ??????? ??? ???????? HR ?? ??? ??????????, ??? ??????? ??? ??????? ????? ????????? ?????? ??? ???????? ?? ??????...

  18. Reduction of initial stress stiffening by topology optimization

    DEFF Research Database (Denmark)

    Philippine, M. A.; Sigmund, Ole; Rebeiz, G. M.; Kenny, T. W.

    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 ...

  19. Large-scale experimental investigation of the effect of biaxial loading on the deformation capacity of pipes with defects

    Energy Technology Data Exchange (ETDEWEB)

    Ostby, Erling [SINTEF Materials and Chemistry, N-7465 Trondheim (Norway)], E-mail: erling.ostby@sintef.no; Hellesvik, Asle O. [SINTEF Materials and Chemistry, N-7465 Trondheim (Norway)

    2008-11-15

    This paper presents results from large-scale four-point bending tests of 12'' X65 seamless pipes with circumferential defects subjected to different levels of internal pressure. The aim of the tests has been to investigate the effect of biaxial loading on the strain capacity of the pipes. The results from the tests show a significant effect of the biaxial loading. For cases without internal pressure, the pipes fail due to local buckling on the compression side of the pipe. Upon application of internal pressure the failure mode shifts to fracture from the defect on the tension side. The failure bending strain levels for these cases were 1.5-2.25%, whereas the local buckling occurred at strain levels in the range of 3.5-4%. The main reason for this appears to be that the biaxial loading increases the crack driving force for a given applied strain level. No significant effect of the biaxial loading on the ductile tearing resistance was observed. The results are of great importance for fracture assessment of pressurised pipelines loaded into the plastic region, as the biaxial loading effect observed is not accounted for in current fracture assessment procedures.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-06-01

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

  2. 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 (0speed 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, the chance for successful improvements is high. The promising optical and electrical properties of these epitaxial films may offer a potential alternative strategy for the growth of high quality functional semiconductors on amorphous substrates using biaxial metal buffer layers. (Abstract shortened by UMI.).

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

    Science.gov (United States)

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

    2015-07-01

    In order to meet the growing need for smart bionic devices and epidermal electronic systems, biaxial stretchability is essential for energy storage units. Based on porous single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) (SWCNT/PEDOT) hybrid fiber, we designed and fabricated a biaxially stretchable supercapacitor, which possesses a unique configuration of the parallel buckled hybrid fiber array. Owing to the reticulate SWCNT film and the improved fabrication technique, the hybrid fiber retained its porous architecture both outwardly and inwardly, manifesting a superior capacity of 215 F g-1. H3PO4-polyvinyl alcohol gel with an optimized component ratio was introduced as both binder and stretchable electrolyte, which contributed to the regularity and stability of the buckled fiber array. The buckled structure and the quasi one-dimensional character of the fibers endow the supercapacitor with 100% stretchability along all directions. In addition, the supercapacitor exhibited good transparency, as well as excellent electrochemical properties and stability after being stretched 5000 times.In order to meet the growing need for smart bionic devices and epidermal electronic systems, biaxial stretchability is essential for energy storage units. Based on porous single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) (SWCNT/PEDOT) hybrid fiber, we designed and fabricated a biaxially stretchable supercapacitor, which possesses a unique configuration of the parallel buckled hybrid fiber array. Owing to the reticulate SWCNT film and the improved fabrication technique, the hybrid fiber retained its porous architecture both outwardly and inwardly, manifesting a superior capacity of 215 F g-1. H3PO4-polyvinyl alcohol gel with an optimized component ratio was introduced as both binder and stretchable electrolyte, which contributed to the regularity and stability of the buckled fiber array. The buckled structure and the quasi one-dimensional character of the fibers endow the supercapacitor with 100% stretchability along all directions. In addition, the supercapacitor exhibited good transparency, as well as excellent electrochemical properties and stability after being stretched 5000 times. Electronic supplementary information (ESI) available: SEM images of the twist-first hybrid fiber, TEM images of SWCNT/PEDOT hybrid bundles, Raman spectra and FTIR spectra of the hybrid electrodes, CVs of the pristine, bended and wound supercapacitor, transmittance spectra of the pristine and stretched supercapacitor, demo video of the supercapacitor. See DOI: 10.1039/c5nr03027g

  4. 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.

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

    OpenAIRE

    Chudnovsky, E. M.; Martinez-Hidalgo, X.

    1999-01-01

    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 spin 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...

  6. 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.

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

    CERN Document Server

    Galatola, P

    2001-01-01

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

  8. 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

  9. Biaxial creep deformation of Zircaloy-4 in the high alpha phase temperature range

    International Nuclear Information System (INIS)

    The ballooning response of Zircaloy-4 fuel tubes during a postulated loss-of-coolant accident may be calculated from a knowledge of the thermal environment of the rods and the creep deformation characteristics of the cladding. In support of such calculations biaxial creep studies have been performed on fuel tubes supplied by Westinghouse, Wolverine and Sandvik of temperatures in the alpha phase range. This paper presents the results of an investigation of their respective creep behaviour which has resulted in the formulation of equations for use in LOCA fuel ballooning codes. (author)

  10. 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...

  11. Biaxially aligned MgO - buffer layers on metallic substrates for the deposition of YBCO - thin films

    International Nuclear Information System (INIS)

    The crucial problem of YBCO - thin films on metallic substrates is to reach a sufficient critical current density considerably above a million A/cm2. Simply c - axes oriented growth during deposition is not sufficient, an additional orientation of the crystals in the plane parallel to the substrate is indispensable. Other groups demonstrated the possibility to deposit a biaxially aligned YSZ buffer - layer on polycrystalline Hastelloy substrates by Ion - Beam - Assisted - Deposition (IBAD). The practicability of these buffer layers to deposit biaxially aligned YBCO was established by X - ray pole figures and measurement of the critical current density. Here, a new sputtering procedure to deposit biaxially aligned buffer layers without an ion - beam gun will be presented. First results of the practicability of this deposition procedure and the achieved quality of the buffer layers will be discussed. (orig.)

  12. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-11-08

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

  14. Experiment to measure the effects of biaxial strain on the critical current of NbTi superconductor

    International Nuclear Information System (INIS)

    Twisted multifilament, copper-clad NbTi superconductors have been axially and biaxially strained at 4.2K with a 7.5T background field. A simply-constructed cryogenic loading frame was built and used to strain the conductor. Results on 1.27 mm x 3.13 mm conductor have shown that degradation of less than .3 percent of critical current occurred when the wire was biaxially strained to +3260 ?epsilon in the axial direction and -1875 ?epsilon in the transverse direction. Degradation approaches 3 percent of critical current at approximately 6000 ?epsilon in the axial direction only

  15. Electronic and optical properties in ZnO:Ga thin films induced by substrate stress

    Science.gov (United States)

    Hwang, Younghun; Ahn, Heejin; Kang, Manil; Um, Youngho; Park, Hyoyeol

    2015-12-01

    The effects of biaxial stress in ZnO:Ga thin films on different substrates, e.g., sapphire(0001), quartz, Si(001), and glass have been investigated by X-ray diffraction, atomic force microscopy, and electrical transport and ellipsometric measurements. A strong dependence of orientation, crystallite size, transport, and electronic properties upon the substrate-induced stress has been found. The structural properties indicate that a tensile stress exists in epitaxial ZnO:Ga films grown on sapphire, Si, and quartz, while a compressive stress appears in films grown on glass. The resistivity of the films decreased with increasing biaxial stress, which is inversely proportional to the product of the carrier concentration and Hall mobility. The refractive index n was found to decrease with increasing biaxial stress, while the optical band gap E0 increased with stress. These behaviors are attributed to lattice contraction and the increase in the carrier concentration that is induced by the stress. Our experimental data suggest that the mechanism of substrate-induced stress is important for understanding the properties of ZnO:Ga thin films and for the fabrication of devices which use these materials.

  16. 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)

  17. Deposition of biaxially textured yttria-stabilized zirconia by ion-beam-assisted deposition.

    Energy Technology Data Exchange (ETDEWEB)

    Chudzik, M. P.

    1998-09-17

    Biaxially textured yttria (8 mol %)-stabilized zirconia (YSZ) thin films were deposited on randomly oriented Hastelloy C and Stainless Steel 304 at room temperature as a buffer layer for subsequent deposition of oriented YBa{sub 2}Cu{sub 3}O{sub x} films. The 0.16-1.3 {micro}m thick YSZ films were deposited by e-beam evaporation at rates of 1.2-3.2 {angstrom}/sec. Biaxially textured films were produced with an Ar/O{sub 2} ion beam directed at the substrate during film growth. X-ray diffraction was used to study in-plane and out-of-plane orientation as a function of ion-bombardment angle, film thickness, ion-to-atom flux ratio, and substrate material. In-plane and out-of-plane average-misorientation angles on these YSZ films that were deposited by ion-beam-assisted deposition were as low as 17 and 5.4{degree}, respectively, on as-received substrates.

  18. Validity of the bi-axial dependence concept: a test in the US general population.

    Science.gov (United States)

    Hasin, D S; Muthuen, B; Wisnicki, K S; Grant, B

    1994-05-01

    According to the "bi-axial" concept of alcohol dependence, the Alcohol Dependence Syndrome (ADS) constitutes an axis or dimension of alcohol difficulties, while other alcohol-related problems (social, legal, etc.) constitute one or more separate dimensions. The validity of the bi-axial distinction was investigated in a stratified probability sample of 3212 US current drinkers who were interviewed in their households. Indicators of the Alcohol Dependence Syndrome and potentially distinct alcohol-related problems were covered in a structured interview administered by carefully trained interviewers. This interview provided extensive coverage of drinking patterns and problems. Aspects of the ADS covered included narrowing, salience, tolerance, withdrawal, withdrawal relief/avoidance and compulsion/control. Other alcohol problems included difficulties with work, health, the law, general social difficulties and problems in marriage/home life. Confirmatory and exploratory factor analyses were used to determine whether a single factor (dimension) or two or more factors fit the data best. Using all methods, we found that one general factor explained the structure of the data better than a two-factor model or other models for males, females, blacks and whites. Thus, the utility of this approach to distinguishing between types of alcohol problems was challenged, raising some questions about abuse/dependence distinctions in various nomenclatures. PMID:8044123

  19. 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.

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

    DEFF Research Database (Denmark)

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

    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...

  1. 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.

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

    Science.gov (United States)

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

    2015-09-01

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

  3. 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

  4. The Landau-de Gennes theory of nematic liquid crystals: Uniaxiality versus Biaxiality

    KAUST Repository

    Majumdar, Apala

    2011-12-01

    We study small energy solutions within the Landau-de Gennes theory for nematic liquid crystals, subject to Dirichlet boundary conditions. We consider two-dimensional and three-dimensional domains separately. In the two-dimensional case, we establish the equivalence of the Landau-de Gennes and Ginzburg-Landau theory. In the three-dimensional case, we give a new definition of the defect set based on the normalized energy. In the threedimensional uniaxial case, we demonstrate the equivalence between the defect set and the isotropic set and prove the C 1,?-convergence of uniaxial small energy solutions to a limiting harmonic map, away from the defect set, for some 0 < a < 1, in the vanishing core limit. Generalizations for biaxial small energy solutions are also discussed, which include physically relevant estimates for the solution and its scalar order parameters. This work is motivated by the study of defects in liquid crystalline systems and their applications.

  5. Biaxially textured yttria stabilized zirconia buffer layers on rotating cylindrical surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, J.; Dzick, J.; Wiesmann, J.; Heinemann, K.; Garcia-Moreno, F.; Freyhardt, H.C. [Institut fuer Metallphysik, Universitaet Goettingen, Hospitalstr. 3-7, D-37073, Goettingen (Germany)

    1997-03-01

    Biaxially textured yttria stabilized zirconia (YSZ) buffer layers are prepared on rotating cylindrical surfaces by an ion-beam-assisted deposition (IBAD) process. A large fraction of the cylinder surface can be coated at the same time, resulting in an effective deposition rate of 40 nm/h for the whole tube circumference (diameter of the tube 12 mm). The in-plane alignment depends on the total film thickness and the rotation velocity. The best in-plane textures achieved so far with a FWHM value of 27{degree} are sufficient for the preparation of YBaCuO films with critical current densities above 10{sup 5} Acm{sup {minus}2} at 77 K and self fields. {copyright} {ital 1997 Materials Research Society.}

  6. Biaxially textured yttria stabilized zirconia buffer layers on rotating cylindrical surfaces

    International Nuclear Information System (INIS)

    Biaxially textured yttria stabilized zirconia (YSZ) buffer layers are prepared on rotating cylindrical surfaces by an ion-beam-assisted deposition (IBAD) process. A large fraction of the cylinder surface can be coated at the same time, resulting in an effective deposition rate of 40 nm/h for the whole tube circumference (diameter of the tube 12 mm). The in-plane alignment depends on the total film thickness and the rotation velocity. The best in-plane textures achieved so far with a FWHM value of 27 degree are sufficient for the preparation of YBaCuO films with critical current densities above 105 Acm-2 at 77 K and self fields. copyright 1997 Materials Research Society

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Geandier, G.; Thiaudière, D.; Randriamazaoro, R. N.; Chiron, R.; Djaziri, S.; Lamongie, B.; Diot, Y.; Le Bourhis, E.; Renault, P. O.; Goudeau, P.; Bouaffad, A.; Castelnau, O.; Faurie, D.; Hild, F.

    2010-10-01

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

  9. Biaxial extrusion of polyimide LARC-TPI and LARC-TPI blends

    Science.gov (United States)

    Haghighat, R. Ross; Elandjian, Lucy; Lusignea, Richard W.

    1990-01-01

    Biaxial films of polyimide LARC-TPI and LARC-TPI/liquid crystal polymer Xydar were extruded directly from the melt for the first time via an innovative extrusion technique. Three types of films, neat LARC-TPI, LARC-TPI/10 wt pct and 30 wt pct blends were processed as a part of this NASA-funded program. Processability was greatly enhanced by incorporating Xydar. The coefficient of thermal expansion was reduced from 34 ppm/C for the neat LARC-TPI to 15 ppm/C for the 10 wt pct Xydar blend and ultimately down to 1 to 3 ppm/C for the 30 wt pct blend films in the direction of extrusion. The maximum improvement in stiffness was realized by incorporating 10 wt pct Xydar (2.8 GPa up to 4.9 GPa). Tensile strength, however, experienced a drop as a result of Xydar addition, probably caused by inefficient mixing of the two phases.

  10. Pseudo-dynamic buckling experiments on thin cylindrical shells under biaxial seismic loads

    International Nuclear Information System (INIS)

    A buckling design research program has been carried out to establish seismic design guidelines for a fast breeder reactor. In doing so, the buckling strength of the cylindrical part of the reactor vessel of a fast breeder reactor under horizontal and vertical seismic loads has been clarified. The effects of axial loads on the horizontal seismic responses in pre- and post-buckling states of thin cylindrical shells are investigated. Pseudo-dynamic buckling experiments are performed to study the dynamic buckling characteristics of thin cylindrical structures when subjected to seismic loads. The buckling tests use model cylinders made of an aluminum plate and a biaxial loading test apparatus. The axial seismic loads reduce the lateral load-carrying capacity of the shells in the pre- and post-buckling regions so that they amplify the horizontal response displacement. An amplification factor that accounts for the effects of the vertical loads is presented and its validity is verified experimentally. (orig.)

  11. 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.

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

    International Nuclear Information System (INIS)

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

  13. A high-sensitivity biaxial resonant accelerometer with two-stage microleverage mechanisms

    Science.gov (United States)

    Ding, Hong; Zhao, Jiuxuan; Ju, Bing-Feng; Xie, Jin

    2016-01-01

    This paper presents a design and experimental evaluation of a micro-electro-mechanical system biaxial resonant accelerometer with two-stage microleverage mechanisms. The device incorporates two pairs of double-ended tuning fork resonators coupled to a single proof mass. The two-stage microleverage mechanisms possess a higher amplification factor than single-stage microleverage mechanisms, so that the proposed accelerometer has a high level of sensitivity. In addition, a low level of cross-axis sensitivity is realized because of the decoupling beams. The accelerometer is theoretically analyzed and then simulated in the system level by the finite element method. The device is fabricated in a silicon-on-insulator wafer. The experimental results demonstrate that the average differential sensitivity of the resonant accelerometer is 275 Hz g?1 at a resonant frequency of 290?kHz under a polarization voltage of 5?V. The measured cross-axis sensitivity is lower than 3.4%.

  14. Electronic structure and optical properties of CuAlO2 under biaxial strain

    International Nuclear Information System (INIS)

    An ab initio calculation has been carried out to investigate the biaxial strain ( - 10.71% 2. All the elastic constants (c11, c12, c13, c33) except c44 decrease (increase) during tensile (compressive) strain. The band gap is found to decrease in the presence of tensile as well as compressive strain. The relative decrease of the band gap is asymmetric with respect to the sign of the strain. Significant differences between the parallel and perpendicular components of the dielectric constant and the optical properties have been observed due to anisotropic crystal structure. It is further noticed that these properties are easily tunable by strain. Importantly, the collective oscillation of the valence electrons has been identified for light polarized perpendicular to the c-axis. From calculations, it is clear that the tensile strain can enhance the hole mobility as well as the transparency of CuAlO2. (paper)

  15. 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.

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

    Indian Academy of Sciences (India)

    A K Chaudhary; A Molla; A Asfaw

    2009-10-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-03

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

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

    International Nuclear Information System (INIS)

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

  19. 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.

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

    OpenAIRE

    Mrki?, Saša; Gali?, Kata; Ivankovi?, 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 i...

  1. 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....

  2. Mechanical Behaviour of Woven Graphite/Polyimide Composites with Medium and High Modulus Graphite Fibers Subjected to Biaxial Shear Dominated Loads

    Science.gov (United States)

    Kumose, M.; Gentz, M.; Rupnowski, P.; Armentrout, D.; Kumosa, L.; Shin, E.; Sutter, J. K.

    2003-01-01

    A major limitation of woven fiber/polymer matrix composite systems is the inability of these materials to resist intralaminar and interlaminar damage initiation and propagation under shear-dominated biaxial loading conditions. There are numerous shear test methods for woven fabric composites, each with its own advantages and disadvantages. Two techniques, which show much potential, are the Iosipescu shear and +/- 45 deg tensile tests. In this paper, the application of these two tests for the room and high temperature failure analyses of woven graphite/polyimide composites is briefly evaluated. In particular, visco-elastic micro, meso, and macro-stress distributions in a woven eight harness satin (8HS) T650/PMR-15 composite subjected to these two tests are presented and their effect on the failure process of the composite is evaluated. Subsequently, the application of the Iosipescu tests to the failure analysis of woven composites with medium (T650) and high (M40J and M60J) modulus graphite fibers and PMR-15 and PMR-II-50 polyimide resins is discussed. The composites were tested as-supplied and after thermal conditioning. The effect of temperature and thermal conditioning on the initiation of intralaminar damage and the shear strength of the composites was established.

  3. Mobility enhancement of strained GaSb p-channel metal–oxide–semiconductor field-effect transistors with biaxial compressive strain

    Science.gov (United States)

    Yan-Wen, Chen; Zhen, Tan; Lian-Feng, Zhao; Jing, Wang; Yi-Zhou, Liu; Chen, Si; Fang, Yuan; Wen-Hui, Duan; Jun, Xu

    2016-03-01

    Various biaxial compressive strained GaSb p-channel metal–oxide–semiconductor field-effect transistors (MOSFETs) are experimentally and theoretically investigated. The biaxial compressive strained GaSb MOSFETs show a high peak mobility of 638 cm2/V·s, which is 3.86 times of the extracted mobility of the fabricated GaSb MOSFETs without strain. Meanwhile, first principles calculations show that the hole effective mass of GaSb depends on the biaxial compressive strain. The biaxial compressive strain brings a remarkable enhancement of the hole mobility caused by a significant reduction in the hole effective mass due to the modulation of the valence bands. Project supported by the National Basic Research Program of China (Grant No. 2011CBA00602) and the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. 2011ZX02708-002).

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

    Directory of Open Access Journals (Sweden)

    María Blanca Ros

    2011-09-01

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

  5. Growth of biaxially textured BaxPb1-xTiO3 ferroelectric thin films on amorphous Si3N4

    International Nuclear Information System (INIS)

    We prepared highly aligned, biaxially textured BaxPb1-xTiO3 (PBT) on amorphous Si3N4 by using an ion-beam-assisted deposited MgO as a template layer. PBT was deposited on a biaxially textured MgO using sol-gel synthesis, metal-organic chemical-vapor deposition, and molecular beam epitaxy. The biaxial texture of the PBT was inherited from the MgO template. The reflection high-energy electron diffraction (RHEED) and cross-section transmission electron microscopy (TEM) experiments suggest that exposure of the MgO template to atmospheric moisture before PBT heteroepitaxy resulted in a significant narrowing of the PBT in-plane orientation distribution. The microstructures of the biaxially textured PBT films were analyzed by x-ray diffraction, RHEED, and TEM. The dynamic contact mode electrostatic force microscopy polarization hysteresis loops confirmed that these films are ferroelectric

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

    International Nuclear Information System (INIS)

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

  7. Numerical simulation of the thermodependant viscohyperelastic behavior of polyethylene terephthalate near the glass transition temperature: Prediction of the self-heating during biaxial tension test

    OpenAIRE

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

    2013-01-01

    The poly ethylene terephthalate near the glass transition temperature highlights a strongly non linear elastic and viscous behaviour when biaxially stretched at high strain rates representative of the injection stretch blow moulding process. A non linear visco-hyperelastic model, where characteristics are coupled to the temperature, has already been identified from equi-biaxial tension experimental results. The weak form of the mechanical part of the model is presented and implemented into a ...

  8. Refined crystal field model for the piezospectroscopy analysis of stresses in polycrystalline alumina

    Science.gov (United States)

    Margueron, Samuel; Clarke, David R.

    2015-09-01

    Stresses produce systematic shifts in the R-line luminescence from Cr3+ ions in aluminium oxide. The two calculational models for determining the stress from observed R-line shifts are compared and combined with new measurements, made under a variety of different stress conditions, to determine refined crystal field model parameters for the piezospectroscopic shifts with stress. In addition to previous, well established results, it is found that the R2-luminescence line shifts linearly with the hydrostatic component of stress, (?11 + ?22 + ?33), even under non-hydrostatic stresses. The separation of the R1 and R2 lines is not linear with the non-hydrostatic stress and increases from biaxial to uniaxial stress states. Excellent agreement with experimental data for polycrystalline materials under uniaxial and biaxial stresses was found when averaging the stresses using the Voigt approximation. However, the R2-R1 peak separation may be affected by the stress dependence of the spectral shape or stress relaxation under the highest stresses.

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

    Science.gov (United States)

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

    2007-04-01

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

  10. Active control of residual tool marks for freeform optics functionalization by novel biaxial servo assisted fly cutting.

    Science.gov (United States)

    Zhu, Zhiwei; To, Suet; Zhang, Shaojian

    2015-09-01

    The inherent residual tool marks (RTM) with particular patterns highly affect optical functions of the generated freeform optics in fast tool servo or slow tool servo (FTS/STS) diamond turning. In the present study, a novel biaxial servo assisted fly cutting (BSFC) method is developed for flexible control of the RTM to be a functional micro/nanotexture in freeform optics generation, which is generally hard to achieve in FTS/STS diamond turning. In the BSFC system, biaxial servo motions along the z-axis and side-feeding directions are mainly adopted for primary surface generation and RTM control, respectively. Active control of the RTM from the two aspects, namely, undesired effect elimination or effective functionalization, are experimentally demonstrated by fabricating a typical F-theta freeform surface with scattering homogenization and two functional microstructures with imposition of secondary phase gratings integrating both reflective and diffractive functions. PMID:26368889

  11. 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

  12. Thermal conductivity of biaxial-strained MoS2: sensitive strain dependence and size-dependent reduction rate

    Science.gov (United States)

    Zhu, Liyan; Zhang, Tingting; Sun, Ziming; Li, Jianhua; Chen, Guibin; Yang, Shengyuan A.

    2015-11-01

    The effect of biaxial tensile strain on the thermal transport properties of MoS2 is investigated by combining first-principles calculations and the Boltzmann transport equation. The thermal conductivities of single layer MoS2 are found to be heavily suppressed by the applied strains; even a moderate biaxial tensile strain, 2 ? 4%, could result in a 10 ? 20% reduction in the thermal conductivity. Most interestingly, the reduction rate of thermal conductivity is size-dependent, which is due to different dominant phonon scattering mechanisms at different sizes of MoS2 samples. The sensitive strain dependence of thermal conductivity indicates that strain engineering could be an effective method to enhance the figure of merit for thermoelectric applications of MoS2.

  13. 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: 2.266, year: 2014

  14. 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)

  15. 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; Thiaudière, Dominique; Hild, François; 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...

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

    Science.gov (United States)

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

    2015-07-01

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

  17. Spontaneous ordering of magnetic particles in liquid crystals: From chains to biaxial lamellae

    Science.gov (United States)

    Peroukidis, Stavros D.; Klapp, Sabine H. L.

    2015-07-01

    Using Monte Carlo computer simulations we explore the self-assembly and ordering behavior of a hybrid, soft magnetic system consisting of small magnetic nanospheres in a liquid-crystalline (LC) matrix. Inspired by recent experiments with colloidal rod matrices, we focus on conditions where the sphere and rod diameters are comparable. Already in the absence of a magnetic field, the nematic ordering of the LC can stabilize the formation of magnetic chains along the nematic or smectic director, yielding a state with local (yet no macroscopic) magnetic order. The chains, in turn, increase the overall nematic order, reflecting the complex interplay of the structure formation of the two components. When increasing the sphere diameter, the spontaneous uniaxial ordering is replaced by biaxial lamellar morphologies characterized by alternating layers of rods and magnetic chains oriented perpendicular to the rod's director. These ordering scenarios at zero field suggest a complex response of the resulting hybrid to external stimuli, such as magnetic fields and shear forces.

  18. 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.

  19. Evaluation of Biaxial Mechanical Properties of Aortic Media Based on the Lamellar Microstructure

    Directory of Open Access Journals (Sweden)

    Hadi Taghizadeh

    2015-01-01

    Full Text Available Evaluation of the mechanical properties of arterial wall components is necessary for establishing a precise mechanical model applicable in various physiological and pathological conditions, such as remodeling. In this contribution, a new approach for the evaluation of the mechanical properties of aortic media accounting for the lamellar structure is proposed. We assumed aortic media to be composed of two sets of concentric layers, namely sheets of elastin (Layer I and interstitial layers composed of mostly collagen bundles, fine elastic fibers and smooth muscle cells (Layer II. Biaxial mechanical tests were carried out on human thoracic aortic samples, and histological staining was performed to distinguish wall lamellae for determining the dimensions of the layers. A neo-Hookean strain energy function (SEF for Layer I and a four-parameter exponential SEF for Layer II were allocated. Nonlinear regression was used to find the material parameters of the proposed microstructural model based on experimental data. The non-linear behavior of media layers confirmed the higher contribution of elastic tissue in lower strains and the gradual engagement of collagen fibers. The resulting model determines the nonlinear anisotropic behavior of aortic media through the lamellar microstructure and can be assistive in the study of wall remodeling due to alterations in lamellar structure during pathological conditions and aging.

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

    Science.gov (United States)

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

    2013-02-15

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

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

    International Nuclear Information System (INIS)

    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. (paper)

  2. 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.

  3. Inflation and Bi-Axial Tensile Testing of Healthy Porcine Carotid Arteries.

    Science.gov (United States)

    Boekhoven, Renate W; Peters, Mathijs F J; Rutten, Marcel C M; van Sambeek, Marc R; van de Vosse, Frans N; Lopata, Richard G P

    2016-02-01

    Knowledge of the intrinsic material properties of healthy and diseased arterial tissue components is of great importance in diagnostics. This study describes an in vitro comparison of 13 porcine carotid arteries using inflation testing combined with functional ultrasound and bi-axial tensile testing. The measured tissue behavior was described using both a linear, but geometrically non-linear, one-parameter (neo-Hookean) model and a two-parameter non-linear (Demiray) model. The shear modulus estimated using the linear model resulted in good agreement between the ultrasound and tensile testing methods, GUS = 25 ± 5.7 kPa and GTT = 23 ± 5.4 kPa. No significant correspondence was observed for the non-linear model aUS = 1.0 ± 2.7 kPa vs. aTT = 17 ± 8.8 kPa, p ? 0); however, the exponential parameters were in correspondence (bUS = 12 ± 4.2 vs. bTT = 10 ± 1.7, p > 0.05). Estimation of more complex models in vivo is cumbersome considering the sensitivity of the model parameters to small changes in measurement data and the absence of intraluminal pressure data, endorsing the use of a simple, linear model in vivo. PMID:26598396

  4. 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)

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

    CERN Document Server

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

    2015-01-01

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

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

    Science.gov (United States)

    Scheidegger, Noemy; Ferris, Mark; Phillips, Nigel

    2014-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Tzung, F.

    1979-11-01

    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.

  8. 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.

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

    Science.gov (United States)

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

  10. 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

  11. Effect of surface finishing and storage media on bi-axial flexure strength and microhardness of resin-based composite.

    Science.gov (United States)

    Gordan, Valeria V; Patel, Shreena B; Barrett, Allyson A; Shen, Chiayi

    2003-01-01

    This in vitro study tested the following null hypotheses: (1) surface finishing treatments do not significantly affect the biaxial flexure strength and microhardness of resin-based composites (RBC) and (2) storage media do not significantly affect these physical properties. Discs (81 RBC and 81 UR; 3M/ESPE) were prepared using a circular polyethylene mold (2.4-mm thick x 16.7 mm in diameter) that was polymerized through a Mylar strip and divided into three surface finishing treatment groups: 1 microm aluminum oxide slurry; 15 microm diamond and a Mylar strip. Randomly selected controls for each finishing group were stored at room temperature in individual vials. Test specimens were immersed in water, stored at 37 degrees C for two days and transferred for an additional seven days to one of three aqueous storage media at 37 degrees C: coffee (pH 5.1), cola (pH 2.4) or red wine (pH 3.7). Post immersion (nine days total), the specimens were tested for biaxial flexure strength (BFS) and Vicker's microhardness (VHN). ANOVA and Tukey's HSD test were used for statistical analysis. ANOVA results indicated that surface finishing treatments had a significant effect on the biaxial flexure strength and microhardness of the RBC and the UR specimens. BFS results for RBC specimens were AL>DD>ML (pML (p<0.0001). Storage in wine medium reduced the VHN of UR specimens significantly. Both alternative hypotheses were accepted. In addition, the Mylar finishing group, because of the resin-rich surface layer, yielded the lowest mean values of BFS and VHN. PMID:14531602

  12. Polarization properties of lasing near an optical axis in the KGd(WO4)2:Nd biaxial crystal

    International Nuclear Information System (INIS)

    Fluorescence and stimulated emission were obtained for propagation directions in the vicinity of the optical axis from the biaxial Nd-doped KGd(WO4)2 crystal. We visualized the peculiar role of the optical axis by fluorescence conoscopy. A fourth spectroscopic parameter due to the monoclinic symmetry was exhibited. Intra-laser-cavity conoscopy was performed in conjunction with the lasing in order to indicate the role of the elliptical modes. The lasing efficiency was found to be in agreement with the relative intensity of the left and right circular polarized components of the fluorescence near the optical axis. (letter)

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

    OpenAIRE

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

    2012-01-01

    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 composite 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 a...

  14. Alternating domains with uniaxial and biaxial magnetic anisotropy in epitaxial Fe films on BaTiO3

    Science.gov (United States)

    Lahtinen, Tuomas H. E.; Shirahata, Yasuhiro; Yao, Lide; Franke, Kévin J. A.; Venkataiah, Gorige; Taniyama, Tomoyasu; van Dijken, Sebastiaan

    2012-12-01

    We report on domain formation and magnetization reversal in epitaxial Fe films on ferroelectric BaTiO3 substrates with ferroelastic a-c stripe domains. The Fe films exhibit biaxial magnetic anisotropy on top of c domains with out-of-plane polarization, whereas the in-plane lattice elongation of a domains induces uniaxial magnetoelastic anisotropy via inverse magnetostriction. The strong modulation of magnetic anisotropy symmetry results in full imprinting of the a-c domain pattern in the Fe films. Exchange and magnetostatic interactions between neighboring magnetic stripes further influence magnetization reversal and pattern formation within the a and c domains.

  15. Alternating domains with uniaxial and biaxial magnetic anisotropy in epitaxial Fe films on BaTiO3

    OpenAIRE

    T.H.E. Lahtinen; Y. Shirahata; YAO, L; K.J.A. Franke; Venkataiah, G.; T. Taniyama; Dijken, S. van

    2012-01-01

    We report on domain formation and magnetization reversal in epitaxial Fe films on ferroelectric BaTiO3 substrates with ferroelastic a-c stripe domains. The Fe films exhibit biaxial magnetic anisotropy on top of c domains with out-of-plane polarization, whereas the in-plane lattice elongation of a domains induces uniaxial magnetoelastic anisotropy via inverse magnetostriction. The strong modulation of magnetic anisotropy symmetry results in full imprinting of the a-c domain pattern in the Fe f...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-03-15

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

  17. 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

  18. 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)

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

    International Nuclear Information System (INIS)

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

  20. Energetical and multiscale approaches for the definition of an equivalent stress for magneto-elastic couplings

    Energy Technology Data Exchange (ETDEWEB)

    Hubert, Olivier, E-mail: hubert@lmt.ens-cachan.f [LMT-Cachan, ENS Cachan, CNRS, UPMC, PRES Universud Paris, 61, avenue du president Wilson, 94235 Cachan Cedex (France); Daniel, Laurent, E-mail: laurent.daniel@supelec.f [Laboratoire de Genie Electrique de Paris (LGEP), CNRS (UMR 8507), SUPELEC, Univ Paris-Sud, UPMC, Plateau du Moulon, 11 rue joliot-Curie, 91192 Gif sur Yvette Cedex (France)

    2011-07-15

    A main limitation of most models describing the effect of stress on the magnetic behavior is that they are restricted to uniaxial - tensile or compressive - stress. Nevertheless, stress is multiaxial in most of industrial applications. An idea to overcome the strong limitation of models is to define a fictive uniaxial stress, the equivalent stress, that would change the magnetic behavior in a similar manner than a multiaxial stress. A first definition of equivalent stress, called the deviatoric equivalent stress, is proposed. It is based on an equivalence in magneto-elastic energy. This formulation is first derived for isotropic materials under specific assumptions. An extension to orthotropic media under disoriented magneto-mechanical loading is made. A new equivalent stress expression, called generalized equivalent stress, is then proposed. It is based on an equivalence in magnetization. Inverse identification of equivalent stress is made possible thanks to a strong simplification of the description of the material seen as an assembly of elementary magnetic domains. It is shown that this second proposal is a generalization of the deviatoric expression. Equivalent stress proposals are compared to former proposals and validated using experimental results carried out on an iron-cobalt sheet submitted to biaxial mechanical loading. These results are compared to the predictions obtained thanks to the equivalent stress formulations. The generalized equivalent stress is shown to be a tool able to foresee the magnetic behavior of a large panel of materials submitted to multiaxial stress. - Research highlights: Classical magneto-elastic models restricted to uniaxial stress. Stress demonstrated multiaxial in most of industrial applications. Proposals of deviatoric and generalized equivalent stresses - multidomain modeling. Experimental validation using iron-cobalt sheet submitted to biaxial loading. Generalization of former proposals and modeling of previous results.

  1. Energetical and multiscale approaches for the definition of an equivalent stress for magneto-elastic couplings

    International Nuclear Information System (INIS)

    A main limitation of most models describing the effect of stress on the magnetic behavior is that they are restricted to uniaxial - tensile or compressive - stress. Nevertheless, stress is multiaxial in most of industrial applications. An idea to overcome the strong limitation of models is to define a fictive uniaxial stress, the equivalent stress, that would change the magnetic behavior in a similar manner than a multiaxial stress. A first definition of equivalent stress, called the deviatoric equivalent stress, is proposed. It is based on an equivalence in magneto-elastic energy. This formulation is first derived for isotropic materials under specific assumptions. An extension to orthotropic media under disoriented magneto-mechanical loading is made. A new equivalent stress expression, called generalized equivalent stress, is then proposed. It is based on an equivalence in magnetization. Inverse identification of equivalent stress is made possible thanks to a strong simplification of the description of the material seen as an assembly of elementary magnetic domains. It is shown that this second proposal is a generalization of the deviatoric expression. Equivalent stress proposals are compared to former proposals and validated using experimental results carried out on an iron-cobalt sheet submitted to biaxial mechanical loading. These results are compared to the predictions obtained thanks to the equivalent stress formulations. The generalized equivalent stress is shown to be a tool able to foresee the magnetic behavior of a large panel of materials submitted to multiaxial stress. - Research highlights: ? Classical magneto-elastic models restricted to uniaxial stress. ? Stress demonstrated multiaxial in most of industrial applications. ? Proposals of deviatoric and generalized equivalent stresses - multidomain modeling. ? Experimental validation using iron-cobalt sheet submitted to biaxial loading. ? Generalization of former proposals and modeling of previous results.

  2. Residual stress and fracture of laminated ceramic membranes

    International Nuclear Information System (INIS)

    Bilayer laminated ceramic membranes were produced comprising a layer of gadolinia-doped ceria (CGO) 180 microm thick and a layer of yttria-stabilized zirconia (YSZ) 5 microm thick. The residual stresses in the laminates at room temperature were estimated from their curvature and the elastic constants of the individual layers. The fracture of the laminates was studied in biaxial flexure at 35 and 800 C. The mean failure stress in the CGO in the laminates was much greater than in unlaminated CGO. This is due partly to an improved microstructure from the lamination process and partly to the restraint of the compressively stressed YSZ. The combined effects of higher failure stress and residual stresses lead to the laminated membranes having higher apparent strength than single layer CGO membranes by factors of between 1.75 and 4.06

  3. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-14

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

  5. 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.

  6. Texture mechanisms and microstructure of biaxial thin films grown by oblique angle deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shetty, A.R.; Karimi, A. [Institut de Physique de la Matiere Condensee (IPMC), Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland)

    2012-08-15

    In order to understand the texture formation mechanism in thin films grown under oblique angle deposition (OAD), TiAlN films were deposited at room temperature (RT) under various incident angles. We show that both in-plane and out-of-plane crystallographic orientations respond strongly to the deposition angle. For {alpha} = 0 , the pole figures show a (111) and (200) mixed out-of-plane orientation with random in-plane alignment. In contrast, under OAD, inclined textures are observed with the (111) direction moving toward the incident flux direction and the (200) moving away, showing substantial in-plane alignment. This observation suggests that TiAlN crystals prefer to grow with the (200) direction perpendicular to the substrate while maintaining the minimization of the surface free energy by maximizing the (111) surface area toward the incident flux. The in-plane texture, which is randomly oriented at normal incidence, gives rise to two preferred orientations under oblique angles - one along the direction of flux and other away from the deposition source. The biaxial texture results from a competition among texture mechanism related to surface mobilities of adatoms, geometrical and directional effects. The surface and cross-section of the films were observed by scanning electron microscopy (SEM). OAD films develop a kind of smooth tiles of a roof structure, with no faceted crystallites. The columns of these films were tilted toward the direction of incident flux. The dependence of (111) texture tilt angle and column angle {beta} on the incidence flux angle {alpha} is evaluated using four well-known models. Transmission electron microscopy (TEM) study reveals a voided, intercolumnar structure with oblique growth toward the flux direction. The selected area diffraction pattern (SAED) pattern supports the pole figure observations. Measurements of the nanoindentation test were performed in order to discuss the change of mechanical properties as a function of incident flux angle. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Development of a hysteresis model for R/C columns subjected to bi-axial lateral loading

    International Nuclear Information System (INIS)

    Recent investigations on dynamic response of reinforced concrete (R/C) structures have confirmed that the R/C structural members undergo much more inelastic deformation in each of the two mutually perpendicular directions under bi-directional seismic loading, than that observed only under unidirectional ground motion. To predict the seismic response of R/C structure with fair accuracy demands, a faithful model that can incorporate the effect of biaxial bending interaction in column. This model should not have high computational demand but should adequately reflect the stiffness degrading and strength deterioration characteristics of R/C structural members. Present study is an effort to develop such a bi-directional hysteresis model accounting the effect of interaction between lateral loadings in two orthogonal directions. The development of the present model is based on the yield surface approach and it can incorporate both strength and stiffness degradation characteristics, which is unavoidable in R/C structures during cyclic loading. The performance of the proposed model/ is demonstrated through the prediction of available experimental results of a reinforced concrete column, subjected to biaxial loading. (author)

  8. Refractive index measurements of films with biaxial symmetry. 1. Determination of complex refractive indices using polarized reflectance/transmittance ratio.

    Science.gov (United States)

    Diao, Jie; Hess, Dennis W

    2005-07-01

    A new method to extract complex refractive indices of films with biaxial symmetry from polarized transmission and reflection spectra is described. Theoretical analysis demonstrates that the reflectance/transmittance ratio (R/T ratio) of two films of different thicknesses but with the same optical anisotropy is a simple function of the refractive index (n) and extinction coefficient (k). For films with biaxial symmetry, components of n and k on symmetric axes can be extracted from either s- or p-polarized R/T ratios if the film thickness values are known. The R/T ratio method can generate n and k spectra within a particular wavelength range without assuming a specific relationship among n, k, and wavelength, which is an advantage over many currently available techniques. The R/T ratio method is used to extract the anisotropic complex refractive indices of a polyimide film with known uniaxial symmetry. The resultant n and k spectra compare well with simulations based on known n and k values. The accuracy of n and k spectra is affected mostly by data error in reflection and transmission spectra collection, thickness variation across sample films, and error in sample alignment. PMID:16852588

  9. Effect of high temperature, biaxial stretching on the thermal and mechanical properties of HDPE/MWCNT sheet

    Science.gov (United States)

    Xiang, Dong; Harkin-Jones, Eileen; Linton, David

    2015-05-01

    High density polyethylene (HDPE)/multi-walled carbon nanotube (MWCNT) composites containing 4 wt% MWCNTs were prepared by melt mixing followed by compression moulding into sheet. Compression moulded sheets were heated to just below the melting temperature and biaxially stretched at ratios (SRs) of 2, 2.5 and 3.0. The effect of stretching on the thermal and mechanical properties of the sheet was studied by differential scanning calorimetry (DSC) and tensile testing. DSC results show that the crystallinity of all the stretched samples increases by approximately 13% due to strain induced crystallization. The melting temperature of the biaxially stretched samples increases only slightly while crystallization temperature is not affected. Tensile test results indicate that at a SR of 2.5 the elastic modulus of the stretched composites increases by 17.6% relative to the virgin HDPE, but the breaking strength decreases by 33%. While the elastic modulus and breaking strength of the HDPE/MWCNT samples continue to increase as SR increases they drop off after a SR of 2.5 for the virgin HDPE. This is probably due to the constraining influence of the nanotubes preventing the relaxation of polymer chains caused by adiabatic heating at high SRs. The addition of MWCNTs results in significant strain hardening during deformation. While this will lead to increased energy requirement in forming it will also result in a more stable process and the ability to produce deep draw containers with more uniform wall thickness.

  10. Synthesis, structuring and characterization of rare earth oxide thin films: Modeling of the effects of stress and defects on the phase stability

    International Nuclear Information System (INIS)

    This work studies the effects of the deposition parameters on the microstructure and the related residual stress in a rare earth oxide thin film. This study is focused on the yttrium sesquioxide (Y2O3) thin films deposited on Si (100) substrates using the ion beam sputtering technique. This technique allows the control of the microstructure and the related residual stress in the thin films by monitoring the energy of the argon beam used in the deposition process. Measurements of the stresses within the oxide layer were performed by the X-ray diffraction-sin2Ψ method. The results show that the classic model of a pure biaxial in-plane model of stress, generally proposed in thin films, is not satisfying. A model that includes a hydrostatic stress due to the crystalline defects generated during the deposition process and a biaxial stress called a fixation stress, gives a good agreement with the experimental results. This modeling of the residual stress, based on nanometer-scale inclusions (point, extended defects) inducing a hydrostatic stress field, leads to a quantitative analysis of the nature and the concentration of the defects. This work shows results that establish a relationship between residual stress, defects and non-equilibrium phase stabilization during growth. - Highlights: • Microstructure of Y2O3 thin films • Measurements of residual stresses in the thin films • Modeling of a triaxial residual stress state • Stress-induced stabilization of non-equilibrium phase

  11. 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

  12. Consistent Parameters for Plastic Anisotropy of Sheet Metal (Part 1-Uniaxial and Biaxial Tests)

    International Nuclear Information System (INIS)

    The anisotropy parameters for sheet metal used hitherto are mainly determined by uniaxial tensile tests. Such tests, however, do not give sufficient information about the yield locus and the forming behaviour in that range where the two principal tensile stresses are of similar magnitude like in stretch forming. The same applies for combined tensile and compressive stress like in deep-drawing. To fill these gaps, new parameters are defined. Their experimental determination is briefly discussed.The 'equibiaxial yield stress' and 'equibiaxial anisotropy' which refer to equibiaxial tensile stress can be determined by cross tensile tests. However, these require a special apparatus. Alternatively experiments for obtaining plane strain can be applied for determining the equibiaxial parameters indirectly. This is possible using conventional tensile testing machines. In this case also anisotropy parameters for plane-strain deformation, the 'semibiaxial anisotropy' in rolling and transverse direction, can be determined

  13. Consistent Parameters for Plastic Anisotropy of Sheet Metal (Part 1-Uniaxial and Biaxial Tests)

    Science.gov (United States)

    Pöhlandt, K.; Lange, K.; Banabic, D.; Schöck, J.

    2007-04-01

    The anisotropy parameters for sheet metal used hitherto are mainly determined by uniaxial tensile tests. Such tests, however, do not give sufficient information about the yield locus and the forming behaviour in that range where the two principal tensile stresses are of similar magnitude like in stretch forming. The same applies for combined tensile and compressive stress like in deep-drawing. To fill these gaps, new parameters are defined. Their experimental determination is briefly discussed. The "equibiaxial yield stress" and "equibiaxial anisotropy" which refer to equibiaxial tensile stress can be determined by cross tensile tests. However, these require a special apparatus. Alternatively experiments for obtaining plane strain can be applied for determining the equibiaxial parameters indirectly. This is possible using conventional tensile testing machines. In this case also anisotropy parameters for plane-strain deformation, the "semibiaxial anisotropy" in rolling and transverse direction, can be determined.

  14. Fracture of thin-walled bodies with crack under biaxial loading

    Science.gov (United States)

    Bastun, V. N.

    1994-07-01

    The influence of the load applied parallel to the crack on the fracture stress oriented perpendicular to the crack in thin-walled circular cylindrical shells with a longitudinal through slot has been investigated. The shells, made from titanium alloys of two brands and low-carbon steel, were subjected to static and cyclic loading by axial force and internal pressure at their various ratios. It is shown that the longitudinal tensile load in definite limits causes an increase of fracture stress and durability along with a decrease of the crack growth rate. The opposite result is obtained when the applied load is compressive. Experimental values of fracture stresses are compared with those calculated under the assumption that the crack surface energy density or the critical value of the J-integral is independent of the stress state mode.

  15. a Prism Coupling Study of Optical Anisotropy in Polyimide Including Moisture, Stress, and Thickness Effects.

    Science.gov (United States)

    Noe, Susan Cunningham

    The study focuses on polymer systems which are currently used in microelectronics, particularly the commercially available polyimides: BTDA-ODA/MPDA (made from benzophenone tetracarboxylic dianhydride and the diamines oxydianiline and meta-phenylene diamine); PMDA-ODA (made from pyromellitic dianhydride and oxydianiline); and BPDA-PDA (made from biphenyl dianhydride and para-phenylene diamine). The non-destructive planar optical waveguiding technique of prism coupling is used to measure the film thickness and the in-plane (nTE) and out-of-plane (nTM) refractive indices at a wavelength of 0.63 mu m (HeNe laser). The film birefringence is calculated as the difference between nTE and nTM. Birefringence values confirm that the polymer chains in the solvent-cast films are preferentially oriented in plane, leading to a transverse isotropic film geometry. Film birefringence is shown to correlate qualitatively with the rigid-rod nature of the polyimide. A suspended membrane load-deflection technique is used to measure the in-plane biaxial stress and the in-plane biaxial modulus of the films. Film properties are measured on adhered films, which are in a state of residual stress, free films, which are in a zero-stress state, and on films which are biaxially stretched to an intermediate stress state. Use of the empirical model allows data taken on adhered films, at several humidities, to be analyzed to extract values of zero-stress birefringence and stress -optic coefficient. The extrapolated zero-stress birefringence is confirmed with free film measurements, and the stress -optic coefficient is confirmed with stretched film measurements. Varying the solution dilution and spin speed, to obtain different thickness films, is found to affect the film properties, including birefringence, in-plane coefficient of thermal expansion, and residual biaxial stress, in a way that is correlated with film thickness. Modelling shows that a substrate-mediated through-thickness gradient in film properties could account for the experimentally observed behavior. Optical and mechanical measurements are also made to study the effect of extended cure, simulating re-work, on the polyimide BTDA-ODA/MPDA. The adhered film birefringence is found to increase with extended cure, due to stress and orientation changes in the films. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.) (Abstract shortened by UMI.).

  16. Reduction of initial stress stiffening by topology optimization

    DEFF Research Database (Denmark)

    Philippine, M. A.; Sigmund, Ole; Rebeiz, G. M.; Kenny, T. W.

    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...... 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...

  17. 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 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 combination of dip angle, friction angle and the far field state of stress. A dip angle of 30 degrees affected the major principal stress most, while the minor principal stress is most affected by a dip angle of 45 degrees, for a friction angle of 10 degrees. The results from the simulation of a thick zone showed that the elastic properties of the zone material mainly affect the stresses within the zone. However, higher values of Young's modulus and Poisson's ratio in the zone than in the side rock resulted in higher stresses within the zone than outside. The orientation of the major principal stress becomes more perpendicular to the zone. The 3-dimensional analyses using 3DEC was made in order to investigate if the stresses at Aespoe could be correlated with the major geological structures. The results show that the increase in the horizontal stress seen both in KAS02 and KAS03 is obtained in the model when using a bilinear stress state that is based on the measurements performed at Aespoe. However, a satisfying coincidence is not obtained with the measured stresses in KAS02, KAS03, KAS05 and KZXSD8HL, which were the boreholes used as reference boreholes. One of the reasons for the disagreement may mainly be that the discontinuities used in the 3DEC model are more or less vertical. The least dip angle used is 60 degrees. Another reason may be that the measured stresses are influenced by far more parameters than are used in the 3DEC-model, such as different rock types, smaller discontinuities and mineral grains

  18. Stress and stress counselling.

    OpenAIRE

    Matheson, K. H.

    1990-01-01

    This is a report by the 1989 National Association of Clinical Tutors Wyeth Travelling Fellow to the United States of America. The stresses of postgraduate training and attempts to modify these are described, including stress counselling. The significance of stress and the relevance of the findings for postgraduate training in the United Kingdom are considered.

  19. Understanding Nonlinear Dielectric Properties in a Biaxially Oriented Poly(vinylidene fluoride) Film at Both Low and High Electric Fields.

    Science.gov (United States)

    Li, Yue; Ho, Janet; Wang, Jianchuan; Li, Zhong-Ming; Zhong, Gan-Ji; Zhu, Lei

    2016-01-13

    Understanding nonlinear dielectric behavior in polar polymers is crucial to their potential application as next generation high energy density and low loss dielectrics. In this work, we studied nonlinear dielectric properties of a biaxially oriented poly(vinylidene fluoride) (BOPVDF) film under both low and high electric fields. For fundamental nonlinear dielectric constants at low fields (PVDF crystals, which had a clear origin of ferroelectric switching of polar crystalline dipoles and domains and nonpolar-to-polar (? ? ? ? ?) phase transformations. By using HVBDS, it was observed that the ferroelectric switching of polar crystalline dipoles and domains in BOPVDF above the EC always took place between 20 and 500 Hz regardless of a broad range of temperature from -30 to 100 °C. This behavior was drastically different from that of the amorphous PVDF dipoles, which had a strong dependence on frequency over orders of magnitude. PMID:26698912

  20. 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...

  1. 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.

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

    Science.gov (United States)

    Behera, Harihar; Mukhopadhyay, Gautam

    2014-02-01

    Our first-principles full-potential density functional theory calculations show that a ZnS monolayer (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 (?). ML-ZnS gets buckled for compressive strain greater than 0.92% ; the buckling parameter ?(= 0.00 Å for planar ML-ZnS) linearly increases with increasing compressive strain (? = 0.435 Å at ? = -5.25%). A tensile strain of 2.91% turns the direct ML-ZnS band gap into indirect. Within our considered strain values of |?| sensors and other nano-devices such as nano-electromechanical systems and nano-optomechanical systems.

  3. Biaxial mechanical properties of the human thoracic and abdominal aorta, common carotid, subclavian, renal and common iliac arteries.

    Science.gov (United States)

    Kamenskiy, Alexey V; Dzenis, Yuris A; Kazmi, Syed A Jaffar; Pemberton, Mark A; Pipinos, Iraklis I; Phillips, Nick Y; Herber, Kyle; Woodford, Thomas; Bowen, Robert E; Lomneth, Carol S; MacTaggart, Jason N

    2014-11-01

    The biomechanics of large- and medium-sized arteries influence the pathophysiology of arterial disease and the response to therapeutic interventions. However, a comprehensive comparative analysis of human arterial biaxial mechanical properties has not yet been reported. Planar biaxial extension was used to establish the passive mechanical properties of human thoracic (TA, [Formula: see text]) and abdominal (AA, [Formula: see text]) aorta, common carotid (CCA, [Formula: see text]), subclavian (SA, [Formula: see text]), renal (RA, [Formula: see text]) and common iliac (CIA, [Formula: see text]) arteries from 11 deceased subjects ([Formula: see text] years old). Histological evaluation determined the structure of each specimen. Experimental data were used to determine constitutive parameters for a structurally motivated nonlinear anisotropic constitutive model. All arteries demonstrated appreciable anisotropy and large nonlinear deformations. Most CCA, SA, TA, AA and CIA specimens were stiffer longitudinally, while most RAs were stiffer circumferentially. A switch in anisotropy was occasionally demonstrated for all arteries. The CCA was the most compliant, least anisotropic and least frequently diseased of all arteries, while the CIA and AA were the stiffest and the most diseased. The severity of atherosclerosis correlated with age, but was not affected by laterality. Elastin fibers in the aorta, SA and CCA were uniformly and mostly circumferentially distributed throughout the media, while in the RA and CIA, elastin was primarily axially aligned and concentrated in the external elastic lamina. Constitutive modeling provided good fits to the experimental data for most arteries. Biomechanical and architectural features of major arteries differ depending on location and functional environment. A better understanding of localized arterial mechanical properties may support the development of site-specific treatment modalities for arterial disease. PMID:24710603

  4. Effects of core characters and veneering technique on biaxial flexural strength in porcelain fused to metal and porcelain veneered zirconia

    Science.gov (United States)

    Oh, Ju-Won; Song, Kwang-Yeob; Ahn, Seung-Geun; Park, Ju-Mi; Lee, Min-Ho

    2015-01-01

    PURPOSE The purpose of this study was to assess the impact of the core materials, thickness and fabrication methods of veneering porcelain on prosthesis fracture in the porcelain fused to metal and the porcelain veneered zirconia. MATERIALS AND METHODS Forty nickel-chrome alloy cores and 40 zirconia cores were made. Half of each core group was 0.5 mm-in thickness and the other half was 1.0 mm-in thickness. Thus, there were four groups with 20 cores/group. Each group was divided into two subgroups with two different veneering methods (conventional powder/liquid layering technique and the heat-pressing technique). Tensile strength was measured using the biaxial flexural strength test based on the ISO standard 6872:2008 and Weibull analysis was conducted. Factors influencing fracture strength were analyzed through three-way ANOVA (??.05) and the influence of core thickness and veneering method in each core materials was assessed using two-way ANOVA (??.05). RESULTS The biaxial flexural strength test showed that the fabrication method of veneering porcelain has the largest impact on the fracture strength followed by the core thickness and the core material. In the metal groups, both the core thickness and the fabrication method of the veneering porcelain significantly influenced on the fracture strength, while only the fabrication method affected the fracture strength in the zirconia groups. CONCLUSION The fabrication method is more influential to the strength of a prosthesis compared to the core character determined by material and thickness of the core. PMID:26576250

  5. Stress Management

    Science.gov (United States)

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

  6. Childhood Stress

    Science.gov (United States)

    ... for Your Child All About Food Allergies Childhood Stress KidsHealth > For Parents > Childhood Stress Print A A ... and feel stress to some degree. Sources of Stress Stress is a function of the demands placed ...

  7. 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.

  8. Crack growth behavior of aluminum alloy 6061 T651 under uniaxial and biaxial planar testing condition

    Directory of Open Access Journals (Sweden)

    S. Henkel

    2015-10-01

    Full Text Available The crack growth behavior of the aluminum alloy 6061 T651 was investigated using cruciform specimens with a measurement area of 120 x 120 x 2 mm3 with two center crack configurations of the starting notch parallel to one of the loading axes and under an angle of 45°, respectively. For the case with crack direction in one of the loading axes the load ratio R = ?min / ?max as well as the force parallel to the crack direction (resulting in different T-stresses were changed. Crack growth rate was studied under varying T-stress. Also the retardation after single overloads was determined for R = 0.1, R = 0.5 and R = 0.8. As a result a change in T-stress does not significantly affect crack growth rate on high R ratios (R = 0.5 for constant ?F loading. In case of lower R-ratios (R = 0.1 crack growth retardation was observed at presence of a static tensile load parallel to the crack growth direction due to higher influence of crack closure. Furthermore, such tensile load results in longer retardation periods after applying an overload at R = 0.1. Less pronounced overload retardation can be assumed with tensile force FX for R = 0.8 and 1.3 times overloads. Non proportional loading with a phase shift in time between the two axes of 45° and 90° results in a mixed mode situation (mode I / mode II at the crack tip of a crack which is orientated under 45° to the loading axes. Mode I and mode II fractions change during every cycle. A phase change of 45° did not change crack growth significantly compared with proportional load. Crack branching occurred when changing from proportional loading to non-proportional 90° phase shifted loading. The two crack tips of the center crack under 45° divided in 4 crack tips under approximately 90° to the loading axes which were simultaneous propagating for more than 10 mm. Finally, two crack tips propagated faster than the remaining two. The stress intensity factors KI and KII as well as the T-stress where calculated by FEA (ABAQUS. For the 45° crack orientation and the non-proportional load case with 90° phase shift linear elastic FEA calculations show that there are time dependent rotating principal stress axes on the crack tip during one cycle. In the unnotched (uncracked specimen there are fixed principal stress axes also in the phase shifted loading case. The configuration with 4 cracks has a significant higher ?KI than the configuration with two crack tips while ?KII is significantly lower. In addition uniaxial crack growth measurements were performed on SENB specimen in the size of 10 x 20 x 100 mm3 covering the threshold and Paris-region for loading ratios R = 0.1, 0.3, 0.5, 0.8.

  9. Energetical and multiscale approaches for the definition of an equivalent stress for magneto-elastic couplings

    Science.gov (United States)

    Hubert, Olivier; Daniel, Laurent

    2011-07-01

    A main limitation of most models describing the effect of stress on the magnetic behavior is that they are restricted to uniaxial - tensile or compressive - stress. Nevertheless, stress is multiaxial in most of industrial applications. An idea to overcome the strong limitation of models is to define a fictive uniaxial stress, the equivalent stress, that would change the magnetic behavior in a similar manner than a multiaxial stress. A first definition of equivalent stress, called the deviatoric equivalent stress, is proposed. It is based on an equivalence in magneto-elastic energy. This formulation is first derived for isotropic materials under specific assumptions. An extension to orthotropic media under disoriented magneto-mechanical loading is made. A new equivalent stress expression, called generalized equivalent stress, is then proposed. It is based on an equivalence in magnetization. Inverse identification of equivalent stress is made possible thanks to a strong simplification of the description of the material seen as an assembly of elementary magnetic domains. It is shown that this second proposal is a generalization of the deviatoric expression. Equivalent stress proposals are compared to former proposals and validated using experimental results carried out on an iron-cobalt sheet submitted to biaxial mechanical loading. These results are compared to the predictions obtained thanks to the equivalent stress formulations. The generalized equivalent stress is shown to be a tool able to foresee the magnetic behavior of a large panel of materials submitted to multiaxial stress.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-01-01

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

  12. 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 during the 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.

  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. Manage Stress

    Science.gov (United States)

    ... Manage Stress Print This Topic En español Manage Stress Browse Sections The Basics Overview Signs and Health ... of 9 sections The Basics: Benefits of Lower Stress What are the benefits of managing stress? Over ...

  15. Effects of concentration-dependent elastic modulus on the diffusion of lithium ions and diffusion induced stress in layered battery electrodes

    Science.gov (United States)

    He, Y.-L.; Hu, H. J.; Song, Y.-C.; Guo, Z.-S.; Liu, C.; Zhang, J.-Q.

    2014-02-01

    A stress assisted diffusion model considering concentration-dependent elastic modulus of active material has been established for the multi-layered electrodes of lithium batteries. The physical mechanism for the effect of modulus variation on the Li-ion diffusion and corresponding biaxial stress is well elucidated. Moreover, the analytic solutions of maximum stress in both active layer and collector are respectively derived. It has been found that the modulus stiffening gives rise to the additional stress gradient and enhances Li-ion diffusion, therefore to increase the biaxial stress in the plate electrode. In contrast, modulus softening makes the stress assisted diffusion less significant and the corresponding stresses are reduced. These coupled effects are more significant during potentiostatic charging and galvanostatic charging with high charging rates. Moreover, the maximum stress in the active layer is independent of charging process, but depends upon the elastic modulus variation due to Li-ion insertion. Finally, with increasing thickness ratio between collector and active material, the impacts of concentration dependent modulus on the Li-ion diffusion in active layer decreases, whereas this effect on maximum stress in the current collector increases.

  16. Measuring the interface stress: Silver/nickel interfaces

    International Nuclear Information System (INIS)

    Interface stress is a surface thermodynamics quantity associated with the reversible work of elastically straining an internal solid interface. In a multilayered thin film, the combined effect of the interface stress of each interface results in an in-plane biaxial volume stress acting within the layers of the film that is inversely proportional to the bilayer thickness. We calculated the interface stress of an interface between {111} textured Ag and Ni on the basis of direct measurements of the dependence of the in-plane elastic strains on the bilayer thickness. The strains were obtained using transmission x-ray diffraction. Unlike previous studies of this type, we used freestanding films so that there was no need to correct for intrinsic stresses resulting from forces applied by the substrate that can lead to large uncertainties of the calculated interface stress value. Based on the lattice parameters of the bulk, pure elements, an interface stress of -2.02±0.26 N/m was calculated using the x-ray diffraction results from films with bilayer thicknesses greater than 5 nm. This value is somewhat smaller than previous measurements obtained from as-deposited films supported by substrates. For smaller bilayer thicknesses the apparent interface stress becomes smaller in magnitude, possibly due to a loss of layering in the specimens. (c) 1999 Materials Research Society

  17. Field-induced optically isotropic state in bent core nematic liquid crystals: unambiguous proof of field-induced optical biaxiality

    International Nuclear Information System (INIS)

    The behaviour of bent core (BC) nematic liquid crystals was investigated under dc applied electric field. The optically isotropic state of a sample containing BC nematic was observed under application of low dc electric fields. The quality of the dark state when the sample was inserted between two crossed polarizers was found to be superb and it did not change when rotating the sample between the polarizers. The coupling between the net molecular dipole moment and the applied dc electric field was considered as the origin of the out-of-plane switching of the BC molecules resulting in switching from the field-off bright state to the field-on dark state. The field-induced optically isotropic state is an unambiguous proof of the field-induced biaxiality in the BC nematic liquid crystal. A simple model explaining the appearance of the isotropic optical state in BC nematics and the switching of the sample slow axis between three mutually orthogonal directions under dc applied electric field is proposed. (paper)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-05-15

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

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

    Science.gov (United States)

    Ciarletta, P.

    2014-12-01

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

  20. 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)

  1. 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...

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

    International Nuclear Information System (INIS)

    Our first-principles full-potential density functional theory calculations show that a ZnS monolayer (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 (?). ML-ZnS gets buckled for compressive strain greater than 0.92% ; the buckling parameter ?(= 0.00 ? for planar ML-ZnS) linearly increases with increasing compressive strain (? = 0.435 ? at ? = ?5.25%). A tensile strain of 2.91% turns the direct ML-ZnS band gap into indirect. Within our considered strain values of |?| < 6%, the band gap shows linearly decreasing (non-linearly increasing as well as decreasing) variation with tensile (compressive) strain. These predictions (based on our calculations with two atoms per unit cell) may be exploited in future for potential applications in strain sensors and other nano-devices such as nano-electromechanical systems and nano-optomechanical systems. (paper)

  3. 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 precursor. ? Film thickness and chemical interactions affect thermo-mechanical properties.

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

    International Nuclear Information System (INIS)

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

  5. 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

  6. 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

  7. 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...

  8. 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)

  9. Nuclear stress test

    Science.gov (United States)

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

  10. 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.

  11. A Shearing-Stretching Device That Can Apply Physiological Fluid Shear Stress and Cyclic Stretch Concurrently to Endothelial Cells.

    Science.gov (United States)

    Meza, Daphne; Abejar, Louie; Rubenstein, David A; Yin, Wei

    2016-03-01

    Endothelial cell (EC) morphology and functions can be highly impacted by the mechanical stresses that the cells experience in vivo. In most areas in the vasculature, ECs are continuously exposed to unsteady blood flow-induced shear stress and vasodilation-contraction-induced tensile stress/strain simultaneously. Investigations on how ECs respond to combined shear stress and tensile strain will help us to better understand how an altered mechanical environment affects EC mechanotransduction, dysfunction, and associated cardiovascular disease development. In the present study, a programmable shearing and stretching device that can apply dynamic fluid shear stress and cyclic tensile strain simultaneously to cultured ECs was developed. Flow and stress/strain conditions in the device were simulated using a fluid structure interaction (FSI) model. To characterize the performance of this device and the effect of combined shear stress-tensile strain on EC morphology, human coronary artery ECs (HCAECs) were exposed to concurrent shear stress and cyclic tensile strain in the device. Changes in EC morphology were evaluated through cell elongation, cell alignment, and cell junctional actin accumulation. Results obtained from the numerical simulation indicated that in the "in-plane" area of the device, both fluid shear stress and biaxial tensile strain were uniform. Results obtained from the in vitro experiments demonstrated that shear stress, alone or combined with cyclic tensile strain, induced significant cell elongation. While biaxial tensile strain alone did not induce any appreciable change in EC elongation. Fluid shear stress and cyclic tensile strain had different effects on EC actin filament alignment and accumulation. By combining various fluid shear stress and cyclic tensile strain conditions, this device can provide a physiologically relevant mechanical environment to study EC responses to physiological and pathological mechanical stimulation. PMID:26810848

  12. 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.

  13. Wettability and optical properties of O2 and CF4 plasma treated biaxially oriented semicrystalline poly(ethylene terephthalate) films

    International Nuclear Information System (INIS)

    Highlights: ? PET films were treated by low pressure O2 and CF4 plasma. ? Influence of the plasma treatment on optical properties and wettability was examined. ? Aging effects were analyzed by storing the samples at room conditions for 60 days. ? Highly hydrophilic surfaces were made without worsening of optical transmission. - Abstract: Influence of low pressure O2, CF4, and successive O2 and CF4 RF plasma treatment on optical properties and wettability of biaxially oriented semicrystalline poly(ethylene terephthalate) (PET) was examined. Produced by industrial stretch-blow molding PET films of the 300 ?m thickness were chosen for the experiments. Influence of the aging was also investigated by storing plasma treated samples at room conditions for 60 days. It was revealed that O2 plasma treated samples suffered from the hydrophobic recovery and long term improvement of hydrophilicity was only a moderate. Energetic CF4 plasma treatment was able to form a large number of surface active sites which in turn was capable to attach the oxygen containing groups and to increase the hydrophilicity. However, aged for 10–60 days CF4 plasma treated PET films have showed a large scattering of the contact angle values measured on the same surface. Successive O2 and CF4 plasma treatment, despite induced hydrophobicity of as treated films, after 3 days of aging have resulted in highly homogeneous hydrophilic (? ? 20°) surfaces which have retained their hydrophilicity for the entire period of investigation. Moreover, combined plasma treatment of PET films has not influenced significantly the transmission of visible light. So, such a treatment can be considered as beneficial for the production of highly homogeneous hydrophilic surfaces without significant influence on their optical properties.

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

    Directory of Open Access Journals (Sweden)

    Andreia Assis Carvalho

    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 composite 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 (α=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<0.05. 75% ethanol permeant produced higher values of sorption and solubility and lower values of BFS than water (p<0.05. CONCLUSION: Ethanol storage media produced more damage on composite resin than water. In general the LED and QTH curing units using 16 and 20 J/cm² by CM and PD curing modes produced no influence on the sorption, solubility or BFS of the tested resin.

  15. Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Pilania, G., E-mail: gpilania@lanl.gov; Uberuaga, B. P. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2015-03-21

    Here, we investigate the electronic structure, energetics of cation ordering, and effect of biaxial strain on double perovskite CsRbCaZnCl{sub 6} using first-principles calculations based on density functional theory. The two constituents (i.e., CsCaCl{sub 3} and RbZnCl{sub 3}) forming the double perovskite exhibit a stark contrast. While CsCaCl{sub 3} 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, RbZnCl{sub 3} 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 CsRbCaZnCl{sub 6} 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.

  16. 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.

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

    International Nuclear Information System (INIS)

    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

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

    Directory of Open Access Journals (Sweden)

    Jose A. Rodríguez-Gutiérrez

    2014-07-01

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

  19. Experimental evaluation of the pure configurational stress assumption in the flow dynamics of entangled polymer melts

    OpenAIRE

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

    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...

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  2. 1.9% bi-axial tensile strain in thick germanium suspended membranes fabricated in optical germanium-on-insulator substrates for laser applications

    Science.gov (United States)

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

    2015-11-01

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

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

    International Nuclear Information System (INIS)

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

  4. Film stresses and electrode buckling in organic solar cells

    KAUST Repository

    Brand, Vitali

    2012-08-01

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

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

    Science.gov (United States)

    Carvalho, N. C.; Le Floch, J.-M.; Krupka, J.; Tobar, M. E.

    2015-05-01

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

  6. Distribution and Viability of Fetal and Adult Human Bone Marrow Stromal Cells in a Biaxial Rotating Vessel Bioreactor after Seeding on Polymeric 3D Additive Manufactured Scaffolds

    Science.gov (United States)

    Leferink, Anne M.; Chng, Yhee-Cheng; van Blitterswijk, Clemens A.; Moroni, Lorenzo

    2015-01-01

    One of the conventional approaches in tissue engineering is the use of scaffolds in combination with cells to obtain mechanically stable tissue constructs in vitro prior to implantation. Additive manufacturing by fused deposition modeling is a widely used technique to produce porous scaffolds with defined pore network, geometry, and therewith defined mechanical properties. Bone marrow-derived mesenchymal stromal cells (MSCs) are promising candidates for tissue engineering-based cell therapies due to their multipotent character. One of the hurdles to overcome when combining additive manufactured scaffolds with MSCs is the resulting heterogeneous cell distribution and limited cell proliferation capacity. In this study, we show that the use of a biaxial rotating bioreactor, after static culture of human fetal MSCs (hfMSCs) seeded on synthetic polymeric scaffolds, improved the homogeneity of cell and extracellular matrix distribution and increased the total cell number. Furthermore, we show that the relative mRNA expression levels of indicators for stemness and differentiation are not significantly changed upon this bioreactor culture, whereas static culture shows variations of several indicators for stemness and differentiation. The biaxial rotating bioreactor presented here offers a homogeneous distribution of hfMSCs, enabling studies on MSCs fate in additive manufactured scaffolds without inducing undesired differentiation. PMID:26557644

  7. 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...

  8. Multi-mode technique for the determination of the biaxial Y2SiO5 permittivity tensor from 300 to 6?K

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    Yishu Wang

    2015-11-01

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

  10. Clinical evaluation of bi-axial pendulum irradiation and pelvic structure tolerance in radiation therapy of carcinoma of the uterine cervix

    International Nuclear Information System (INIS)

    Between 1965 and 1982 at the Department of Radiology, Jikei University Hospital, 425 patients with carcinoma of the uterine cervix were treated mainly with bi-axial lateral 150 deg pendulum external irradiation. Out of them, 137 cases with sufficient follow-up during the period from 1973 to 1982 were analyzed to evaluated the tolerance of the pelvic structures as well as the results. The cumulative 3-year local control rate was 100 % in stage I (8 cases), 85 % in stage II (33 cases), 60 % in stage III (81 cases), and 0 % in stage IV (15 cases), while the cumulative 5-year survival rate was 69.4 % in stage I, 68.1 % in stage II, 40.6 % in stage III, and 0 % in stage IV. The cumulative incidence of complications was 38.6 % in GII + GIII and 27.0 % in GIII, respectively. Equivalent dose over 120 of TDF at point A had been delivered in most cases that showed late complications requiring medical management. Therefore, the tolerance dose of the pelvic structures in this irradiation technique was supposed to be about 120 of total TDF at point A. We conclude that bi-axial pendulum external irradiation technique should be applied for advanced carcinoma of the uterine cervix which are unsuitable to intracavitary irradiation for social, anatomical, and other medical reasons. (author)

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

    Science.gov (United States)

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

    2015-09-16

    Poly(vinylidene fluoride) (PVDF)-based homopolymers and copolymers are attractive for a broad range of electroactive applications because of their high dielectric constants. Especially, biaxially oriented PVDF (BOPVDF) films exhibit a DC breakdown strength as high as that for biaxially oriented polypropylene films. In this work, we revealed the molecular origin of the high dielectric constant via study of a commercial BOPVDF film. By determination of the dielectric constant for the amorphous phase in BOPVDF, a high value of ca. 21-22 at 25 °C was obtained, and a three-phase (i.e., lamellar crystal/oriented interphase/amorphous region) semicrystalline model was proposed to explain this result. Meanwhile, electronic conduction mechanisms in BOPVDF under high electric fields and elevated temperatures were investigated by thermally stimulated depolarization current (TSDC) spectroscopy and leakage current studies. Space charge injection from metal electrodes was identified as a major factor for electronic conduction when BOPVDF was poled above 75 °C and 20 MV/m. In addition, when silver or aluminum were used as electrodes, new ions were generated from electrochemical reactions under high fields. Due to the electrochemical reactions between PVDF and the metal electrode, a question is raised for practical electrical applications using PVDF and its copolymers under high-field and high-temperature conditions. A potential method to prevent electrochemical degradation of PVDF is proposed in this study. PMID:26120953

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-11

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

  13. 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.

  14. 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

  15. Effect of state of stress on the cavitation behavior of Al 5083 superplastic material

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Namas; Kalu, Peter [Dept. of Mech. Eng., Florida State Univ., Tallahassee, FL (United States); Khraisheh, Marwan K. [Dept. of MEch. Eng., Univ. of Kentucky, Lexington, KY (United States)

    2005-07-01

    In this paper we address the controversial issue of nucleation of cavities in Al 5083 alloys and their subsequent growth to coalescence and failure. We focus on the origin and growth of cavities not only during the primary processing of Al 5083 in sheet forms, but also during the manufacture of these sheets into SPF (superplastic forming) components. Experimental observations of pre-existing cavities in this alloy are made using optical and electron microscopy. The role of sheet rolling direction, and the state of stress during superplastic deformation on the cavity formation and coalescence are also discussed. The effect of the state of stress (uniaxial, plane strain, balanced biaxial, and tri-axial) on the growth characteristics of cavitation is also examined. It is found that the uniaxial model based cavitation cannot directly be extended to predict the behavior of more complex stress states, unless great care is taken to identify the right strain measure for the mapping process. (orig.)

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

    International Nuclear Information System (INIS)

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

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

    DEFF Research Database (Denmark)

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

    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...... (DSC) for the curing behavior, dynamic mechanical analysis (DMA) for the elastic modulus evolution during the 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....

  18. Cold Stress

    Science.gov (United States)

    ... Topics Publications and Products Programs Contact NIOSH COLD STRESS Recommend on Facebook Tweet Share Compartir On this ... cold environments may be at risk of cold stress. Extreme cold weather is a dangerous situation that ...

  19. Caregiver Stress

    Science.gov (United States)

    ... womenshealth.gov/widget/hrsa-widget-en.html Caregiver stress Caregivers care for someone with an illness, injury, ... be rewarding, but it can also be challenging. Stress from caregiving is common. Women especially are at ...

  20. Childhood Stress

    Science.gov (United States)

    ... their day — especially if they've had a stressful day themselves. But expressing interest shows your kids ... journal. You also can help by anticipating potentially stressful situations and preparing kids for them. For example, ...

  1. Stress Management

    Science.gov (United States)

    ... intensity? Seasonal Fitness Target Heart Rates Warm Up, Cool Down When is the best time of day ... Stress Four Ways to Deal With Stress Quit Smoking Quitting Smoking Why Quit Smoking? Smoking: Do you ...

  2. 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.

  3. STRESS ECHOCARDIOGRAPHY

    OpenAIRE

    Salustri, A

    1994-01-01

    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...

  4. Analysis of the biaxial stress-strain behavior of poly(dimethylsiloxane) networks from the viewpoint of the slip-link model of rubber elasticity.

    Czech Academy of Sciences Publication Activity Database

    Meissner, Bohumil; Mat?jka, Libor

    2004-01-01

    Ro?. 42, ?. 17 (2004), s. 2318-2328. ISSN 0887-6266 R&D Projects: GA ?R GA104/00/1311; GA AV ?R IAA4050008 Institutional research plan: CEZ:AV0Z4050913 Keywords : elastomers * entanglements * networks Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.391, year: 2004

  5. 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.…

  6. Stress at work : stress management

    OpenAIRE

    Shchuka, Aljona

    2010-01-01

    Stress has been experienced since ancient times, but it has never been worse than it is here in the early 21st century. Nowadays stress is responsible for more than fifty percent of all illness. Despite this fact, the phenomenon of stress still hasn’t been that deeply studied. Contemporary society has to deal with the relatively new concept of “workplace stress” more and more often. In order to answer the questions as to: “Why?” and “What to do?” the problem of stress should be looked at...

  7. Residual stresses

    International Nuclear Information System (INIS)

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

  8. 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.

  9. 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.

  10. 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...

  11. Development of Biaxially Textured YBa{sub 2}Cu{sub 3}O{sub 7} Coated Conductors in the U.S.

    Energy Technology Data Exchange (ETDEWEB)

    Christen, D.K.; Hawsey, R.A.; Kroeger, D.M.

    1999-11-13

    Two new processes have been under development since 1991 that promise a new, cost-effective way to manufacture flexible, high current density wires made from YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO). The key is to prepare a textured substrate, or ''template,'' on which the YBCO may be deposited as a biaxially aligned thick film. Ion beam assisted deposition (IBAD) of yttria stabilized zirconia or magnesium oxide on alloy tapes enables a final superconducting layer with grain-to-grain, in-plane alignment to within 3-5 degrees. Similar results are achieved on rolling-assisted, biaxially textured substrates (RABiTS) using a variety of oxide layers on textured nickel tapes. The performance of research lengths of prototype wires in strong magnetic fields at 65 K already exceeds that of NbTi and Nb{sub 3}Sn in liquid helium. A scalable, ex-situ process for the YBCO coating has been demonstrated on both types of substrates. Consistent values of critical current density (J{sub c }) greater than 1 x 10{sup 6} A/cm{sup 2} are now obtained on RABiTS, and J{sub c}'s in excess of 2 x 10{sup 6} A/cm{sup 2} have been obtained on both substrates. A nonmagnetic variation of RABiTS (Ni-13% Cr) has also been shown to yield Jc greater than 1.5 x 10{sup 6} A/cm{sup 2} . Six private companies in the U.S. are scaling up YBCO coated conductors for power and physics applications.

  12. Operator stress

    International Nuclear Information System (INIS)

    This paper addresses operator stress in the controlled testing environment of operator licensing accreditation for operation of a nuclear plant facility. From the perspective of stress theory, the authors look at the operator and shift supervisor under accreditation test conditions. They map theory to the real world of nuclear plant operations to reach conclusions concerning the stressfullness of the test situation, and recognize the stress management skills and self control of those operators and shift supervisors who successfully pass the test. (author)

  13. Modeling of delayed strains of concrete under biaxial loadings. Application to the reactor containment of nuclear power plants; Modelisation des deformations differees du beton sous sollicitations biaxiales. application aux enceintes de confinement de batiments reacteurs des centrales nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Benboudjema, F

    2002-12-15

    The prediction of delayed strains is of crucial importance for durability and long-term serviceability of concrete structures (bridges, containment vessels of nuclear power plants, etc.). Indeed, creep and shrinkage cause cracking, losses of pre-stress and redistribution of stresses, and also, rarely, the ruin of the structure. The objective of this work is to develop numerical tools, able to predict the long-term behavior of concrete structures. Thus, a new hydro mechanical model is developed, including the description of drying, shrinkage, creep and cracking phenomena for concrete as a non-saturated porous medium. The modeling of drying shrinkage is based on an unified approach of creep and shrinkage. Basic and drying creep models are based on relevant chemo-physical mechanisms, which occur at different scales of the cement paste. The basic creep is explicitly related to the micro-diffusion of the adsorbed water between inter-hydrates and intra-hydrates and the capillary pores, and the sliding of the C-S-H gel at the nano-porosity level. The drying creep is induced by the micro-diffusion of the adsorbed water at different scales of the porosity, under the simultaneous effects of drying and mechanical loadings. Drying shrinkage is, therefore, assumed to result from the elastic and delayed response of the solid skeleton, submitted to both capillary and disjoining pressures. Furthermore, the cracking behavior of concrete is described by an orthotropic elastoplastic damage model. The coupling between all these phenomena is performed by using effective stresses which account for both external applied stresses and pore pressures. This model has been incorporated into a finite element code. The analysis of the long-term behavior is also performed on concrete specimens and prestressed concrete structures submitted to simultaneous drying and mechanical loadings. (author)

  14. Stress induced martensitic transformation kinetics of polycrystalline NiTi shape memory alloy

    International Nuclear Information System (INIS)

    The variation of semi-empirical volume fraction of martensite as a function of thermodynamic driving force (t.d.f.) is determined based on measurements of pseudo-elastic deformation effects appearing in tubular Ni51at.%-Ti specimens submitted to isothermal biaxial proportional loading. To this end a thermodynamic framework developed by one of the authors (B.R.) was employed. These new experimental results when compared with the predictions of specific formal equations for martensitic phase transformation (p.t.) proposed earlier by B.R., indicate the need for modification of the formula describing the kinetics of reverse p.t. (martensite→austenite) associated with the formation of partial hysteresis in stress-strain co-ordinates. The applied method is new and the results are of importance in macroscopic modelling (determination of appropriate sets of constitutive equations) of the pseudo-elastic behaviour of SMA under complex stress state

  15. 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.)

  16. Stress Testing

    Science.gov (United States)

    ... and symptoms of CHD may occur only during exercise. A stress test can detect the following problems, which may ... especially if they occur at low levels of exercise Abnormal changes in your heart's rhythm or electrical activity During a stress test, if you can't exercise for as ...

  17. Geopotential Stress

    DEFF Research Database (Denmark)

    Schiffer, Christian; Nielsen, S.B.

    Density heterogeneity in the Earth’s lithosphere causes lateral pressure variations. Horizontal gradients of the vertically integrated lithostatic pressure, the Geopotential Energy (GPE), are a source of stresses (Geopotential Stress) that contribute to the Earth’s Stress Field. In theory the GPE...... is linearly related to the lithospheric part of the Geoid. The Geopotential Stress can be calculated if either the density structure and as a consequence the GPE or the lithospheric contribution to the Geoid is known. The lithospheric Geoid is usually obtained by short pass filtering of satellite...... are not entirely suitable for the stress calculations but can be compiled and adjusted. We present an approach in which a global lithospheric density model based on CRUST2.0 is obtained by simultaneously fitting topography and surface heat flow in the presence of isostatic compensation and long...

  18. The effect of the tensile stress on the swelling and microstructure of the stainless steels irradiated to high neutron fluence

    International Nuclear Information System (INIS)

    The void swelling and microstructure of the 0Kh16N15M3B and 0Kh16N15M3BP austenitic steels after irradiation in BN-350 reactor to displacement doze of 60 dpa at 4800C versus the applied stress have been studied. The swelling of those steels was found are linear with the biaxial tensile stress changing over the range 0/196 MPa. Swelling modulus, therewith was equal to 5x10-3MPa-1 and 9.2/15.8x10-3MPa-1 for the 0Kh16N15M3B and OKh16N15M3BP steels respectively. The stress effects the void number density increase without any significant changes of the void size. 2 refs.; 5 figs.; 1 tab. (author)

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

    International Nuclear Information System (INIS)

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

  20. 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.

  1. 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.)

  2. 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)

  3. Biaxial thermal creep of V-4Cr-4Ti at 700 deg. C and 800 deg. C

    International Nuclear Information System (INIS)

    A study of the thermal creep properties of V-4Cr-4Ti were performed using pressurized tube specimens. Creep tubes nominally 4.57 mm OD by 0.25 mm wall thickness were pressurized with high-purity helium gas to mid-wall effective stresses below the uniaxial yield strength. Specimens were heated to 700 deg. C and 800 deg. C in an ultra-high vacuum furnace and periodically removed to measure the change in OD with a high-precision laser profilometer. The secondary creep rate was found to be power-law dependent on the applied stress with a stress exponent of 3.7 at 700 deg. C and 2.7 at 800 deg. C. The average activation energy for creep of V-4Cr-4Ti was 299 kJ/mol, which is quite close to the activation energy for self-diffusion in pure vanadium in this temperature regime. The predominant mechanism of creep deformation for the conditions employed in this study is most likely climb-assisted dislocation motion

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

    International Nuclear Information System (INIS)

    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.

  5. 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.

  6. Residual compressive stress induced infrared-absorption frequency shift of hexagonal boron nitride in cubic boron nitride films prepared by plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Liu, Yong; Jin, Panpan; Chen, Aili; Yang, Hangsheng; Xu, Yabo

    2012-09-01

    The effects of compressive stress on the TO phonon frequencies of hexagonal boron nitride (hBN) in cubic BN (cBN) films were investigated using infrared absorption spectroscopy, showing that the B-N stretching vibration of hBN at 1380 cm-1 shifted to high wavenumbers under biaxial compressive stress with the rate 2.65 cm-1 per GPa, while the B-N-B bending vibration near 780 cm-1 shifted to low wavenumbers with the rate -3.45 cm-1/GPa. The density functional perturbation theoretical calculation was carried out to check the above phonon frequencies under stress for two typical orientations of hBN crystallite. The results are shown to be in fair agreement with the experimental data. Our results suggest that the residual compressive stress accumulated in cBN films can be evaluated from the IR peak position near 780 cm-1.

  7. Effects of crack depth, specimen size, and out-of-plane stress on the fracture toughness of reactor vessel steels: An analytical study

    International Nuclear Information System (INIS)

    Fracture toughness values for A533-B reactor pressure vessel (RPV) steel obtained from test programs at Oak Ridge National Laboratory (ORNL) and University of Kansas (KU) are interpreted using the J-A2 analytical model. The analytical model is based on the critical stress concept and takes into consideration the constraint effect using the second parameter A2 in addition to the generally accepted loading parameter J. It is demonstrated that with the constraint level included in the model effects of crack depth (shallow vs. deep), specimen size (small vs. large), and loading type (uniaxial vs. biaxial) on the fracture toughness from the test programs can be interpreted and predicted

  8. Stressing academia?

    DEFF Research Database (Denmark)

    Opstrup, Niels; Pihl-Thingvad, Signe

    Incongruences between the individual and the organizational work context are potential stressors. The present study focuses on the relationship between a complementary need-supply fit and Danish researchers’ self-perceived job stress. Strain is expected to increase as organizational supplies fall...... short of individual need while high degrees of fit will mitigate stress. The analysis is based on a stratified random sample including 2127 researchers at 64 Danish university departments and covering all main areas of research and all academic staff categories. The results show that fit with regard to...... “soft” dimensions as freedom and independence in the job, personal and professional development at work, and receiving peer recognition is highly significant for the researchers’ self-perceived stress-level. The better the fit is the lower stress-levels the researchers’ on average report. On the other...

  9. Stress incontinence

    OpenAIRE

    Onwude, Joseph Loze

    2009-01-01

    Stress incontinence, involving involuntary leaking of urine on effort, exertion, sneezing, or coughing, affects 17-45% of adult women. Risk factors include pregnancy (especially with vaginal delivery), smoking, and obesity.

  10. ANTIOXIDATIVE STRESS

    OpenAIRE

    DÜNDAR, Y.; ASLAN, R.

    2013-01-01

    Objective: The aim of this short review is to provokefocuses on the antioxidant-induced stress. Althoughthere are studies documenting that supplementationwith antioxidants appears to reduce lipid peroxidationand oxidative stress, it is still unknown exactly whatamounts are needed to have a beneficial antioxidanteffect and which dose reflects the safe and appropri-ate  limit for use. Many of  antioxidant vitamins and theother antioxidants can cause pathologic changes tothe exposed tissues and ...

  11. Oxidative stress

    OpenAIRE

    Burton, Graham J.; Jauniaux, Eric

    2011-01-01

    Considerable evidence implicates oxidative stress in the pathophysiology of many complications of human pregnancy, and this topic has now become a major focus of both clinical and basic science research. Oxidative stress arises when the production of reactive oxygen species overwhelms the intrinsic anti-oxidant defences. Reactive oxygen species play important roles as second messengers in many intracellular signalling cascades aimed at maintaining the cell in homeostasis with its immediate en...

  12. Stress fractures

    International Nuclear Information System (INIS)

    The diagnosis of a stress fracture should be considered in patients presented with pain after a change in activity, especially if the activity is strenuous and the pain is in the lower extremities. Since evidence of the stress fracture may not be apparent for weeks on routine radiographs, proper use of other imaging techniques will allow an earlier diagnosis. Prompt diagnosis is especially important in the femur, where displacement may occur

  13. Pelvic stress.

    Science.gov (United States)

    Nusholtz, G S; Kaiker, P S

    1986-01-01

    Biomechanics testing simulated stress concentrations in the acetabulum resulting from a blow to the right trochanter, as commonly occurs in recreational and passenger contexts. Developing tolerance criteria for the pelvis is addressed in this paper in terms of the load distribution and energy transmission to the pelvis via both soft tissues and the femur, the instability of the femur-pelvis complex, and the difficulty of predicting stress using simple, experimentally derived, parameters. PMID:3818671

  14. Determination of residual stresses through piezo-spectroscopy in the alumina layer localized at the interface of thermal barriers; Determination des contraintes residuelles par piezospectroscopie dans les couches d'alumine a l'interface des barrieres thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Margueron, S.; Lepoutre, F. [Office National d' Etudes et de Recherches Aerospatiales (ONERA), 92 - Chatillon (France)

    2003-03-01

    Thermal barrier coatings (TBC) are ceramics layers deposited on the hot parts of turbines, their low thermal conductivity makes operating temperatures higher and as a consequence improves the turbine global yield. The authors propose a method for measuring the intensity of residual stresses in alumina oxide layer in order to better understand the aging processes that lead to TBC damages. This method has been applied to an AM1 sample covered with a polished underlayer of NiAl (Zr 500 ppm) and then with a TBC made of zircon that has been deposited through EB-PVD (electron beam physical vapour deposition). A series of about 1800 thermal cycles has been performed (operating temperature: 1100 Celsius degrees). An oxide layer has appeared at the interface between TBC and the underlayer. The analysis of fluorescence spectra shows the existence of a stress gradient inside the oxide layer. Moreover a regular pattern of macroscopic ripples can be noticed on the surface of the sample. It seems as if the ripples were due to a diffusion process of matter into the underlayer. Through the method the authors have shown and quantified the existence of: - biaxial residual stresses whose intensity is about -4 GPa, - an important biaxial stress gradient in the oxide layer: 0,95 GPa, and - stresses perpendicular to the interface whose intensity is {+-} 200 GPa. (A.C.)

  15. High-temperature annealing of AlGaN: Stress, structural, and compositional changes

    International Nuclear Information System (INIS)

    The effect of high-temperature annealing on stress in AlxGa1-xN in different ambients and at different temperatures was studied using ultraviolet micro-Raman spectroscopy. Low (x=0.08) and high (x=0.31 and x=0.34) composition AlGaN, grown by metalorganic chemical vapor deposition (MOCVD) and molecular-beam epitaxy (MBE), were compared. Compositional and morphological changes were monitored using Auger electron spectroscopy (AES) and atomic force microscopy (AFM), respectively. The Raman results demonstrate that all samples exhibit maximum stress changes in the compressive direction when annealed in an air ambient. AES confirms this to be due to higher oxygen incorporation after annealing in the air ambient, and shows higher oxygen incorporation in the vicinity of cracks and defects. MOCVD and MBE samples of a similar composition were found to reach the same biaxial stress, despite differences in initial stress and growth temperature. Relaxation of a parabolic intercrack stress profile to homogeneous stress was observed with annealing in all ambients for cracked samples. AFM results on cracked samples show an increase in width of the primary cracks along the directions, and the formation of secondary cracks along the directions

  16. 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)

  17. Imaging stress.

    Science.gov (United States)

    Brielle, Shlomi; Gura, Rotem; Kaganovich, Daniel

    2015-11-01

    Recent innovations in cell biology and imaging approaches are changing the way we study cellular stress, protein misfolding, and aggregation. Studies have begun to show that stress responses are even more variegated and dynamic than previously thought, encompassing nano-scale reorganization of cytosolic machinery that occurs almost instantaneously, much faster than transcriptional responses. Moreover, protein and mRNA quality control is often organized into highly dynamic macromolecular assemblies, or dynamic droplets, which could easily be mistaken for dysfunctional "aggregates," but which are, in fact, regulated functional compartments. The nano-scale architecture of stress-response ranges from diffraction-limited structures like stress granules, P-bodies, and stress foci to slightly larger quality control inclusions like juxta nuclear quality control compartment (JUNQ) and insoluble protein deposit compartment (IPOD), as well as others. Examining the biochemical and physical properties of these dynamic structures necessitates live cell imaging at high spatial and temporal resolution, and techniques to make quantitative measurements with respect to movement, localization, and mobility. Hence, it is important to note some of the most recent observations, while casting an eye towards new imaging approaches that offer the possibility of collecting entirely new kinds of data from living cells. PMID:26139131

  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. 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.

  20. 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.

  1. How light sources and distance of the light tip influence water sorption, solubility, and biaxial flexural strength of a composite resin.

    Science.gov (United States)

    Lopes, Lawrence Gonzaga; Moraes, Beatriz Rodrigues; Souza, Renata Magalhaes P; Jardim Filho, Alfeu da Veiga; Moreira, Francine do Cuoto Lima; Campos, Roberto Elias; de Souza, Joao Batista

    2010-01-01

    This study evaluated the water sorption (WS), solubility (SL), and biaxial flexural strength (BFS) of a resin composite based on different polymerization units, storage permeants (distilled water and 75% ethanol), and distances between the light's tip and the composite resin. Using a stainless steel mold, 80 specimens were made and separated in two independent groups, according to the duration of storage (7 days or 60 days). The specimens were photocured using either a QTH or LED light (both used at 600 mW/cm2 for 40 seconds), with the light's tip guide either 0 mm or 2 mm from the surface of the resin. In general, the 75% ethanol produced higher WS and SL values but lower BFS values compared to water. Both distances influenced the WS and SL values, especially when 75% ethanol was used (p 0.05). For nearly all groups, the WS, SL, and BFS in different solvents and at different distances for photocuring of the tested resin were not affected by the curing light used. PMID:20591764

  2. Biaxially textured copper and copper-iron alloy substrates for use in YBa2Cu3O7-x coated conductors

    International Nuclear Information System (INIS)

    Copper and Cu-Fe (Fe ?2.35 wt%) alloy substrates were thermo-mechanically processed and the biaxial texture development, magnetic properties, yield strength, and electrical resistivity were studied and compared to determine their suitability as substrates for high-temperature superconducting coated conductor applications. Average full width half maximum (FWHM) of 5.50 in Phi scans (in-plane alignment), and 6.60 in omega scans (out-of-plane alignment) was obtained in copper samples. Cu-Fe samples showed 5.90 FWHM in Phi scans and 5.90 in omega scans. Even with the presence of 2.35% Fe in the Cu-alloy, the saturation magnetization (Msat) value was found to be 4.27 emu g-1 at 5 K, which is less than in Ni samples by an order of magnitude and comparable to that of Ni-9 at.% W substrates. The yield strength of the annealed Cu-Fe alloy substrate was found to be at least two times higher than that of similarly annealed copper substrates. The electrical resistivity of Cu-Fe alloy was found to be an order of magnitude higher than that of pure copper at 77 K

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-01-01

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

  4. Three-Dimensional Packing Structure and Electronic Properties of Biaxially Oriented Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2- b ]thiophene) Films

    KAUST Repository

    Cho, Eunkyung

    2012-04-11

    We use a systematic approach that combines experimental X-ray diffraction (XRD) and computational modeling based on molecular mechanics and two-dimensional XRD simulations to develop a detailed model of the molecular-scale packing structure of poly(2,5-bis (3-tetradecylthiophene-2-yl) thieno[3,2-b]thiophene) (PBTTT-C 14) films. Both uniaxially and biaxially aligned films are used in this comparison and lead to an improved understanding of the molecular-scale orientation and crystal structure. We then examine how individual polymer components (i.e., conjugated backbone and alkyl side chains) contribute to the complete diffraction pattern, and how modest changes to a particular component orientation (e.g., backbone or side-chain tilt) influence the diffraction pattern. The effects on the polymer crystal structure of varying the alkyl side-chain length from C 12 to C 14 and C 16 are also studied. The accurate determination of the three-dimensional polymer structure allows us to examine the PBTTT electronic band structure and intermolecular electronic couplings (transfer integrals) as a function of alkyl side-chain length. This combination of theoretical and experimental techniques proves to be an important tool to help establish the relationship between the structural and electronic properties of polymer thin films. © 2012 American Chemical Society.

  5. Use of biaxially oriented polypropylene film for evaluating and cleaning contaminated atomic force microscopy probe tips: An application to blind tip reconstruction

    Science.gov (United States)

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

    2002-11-01

    An atomic force microscopy (AFM) image of a surface is basically a convolution of the probe tip geometry and the surface features; it is important to know this tip effect to ensure that an image truly reflects the surface features. We have found that a biaxially oriented polypropylene (BOPP) film is suitable for checking tip performance and for cleaning contaminated tips, thus making it possible to collect images of the same area of a BOPP film surface before and after the tip was cleaned. Therefore, the difference between the two different images is solely due to the contamination of the tip. We took advantage of our ability to collect AFM images of the same area using the same tip, in one instance, contaminated and, in the other, after being cleaned. First we used blind reconstruction on the image collected using the contaminated tip. Blind tip reconstruction allows one to extract the geometry of the tip from a given image. Once we had estimated the geometry of the contaminated tip, we used it to simulate the tip effect using the image collected using the cleaned tip. By comparing the simulation result with the image collected using the contaminated tip we showed that the blind reconstruction routine works well. Prior to this, there was no de facto method for testing blind reconstruction algorithms.

  6. Stress Analysis

    DEFF Research Database (Denmark)

    Burcharth, Hans F.

    The following types of forces contribute to the stresses in a Dolos in a pack exposed to waves: 1)Gravity forces Compaction forces (mainly due to settlements, gravity and flow forces) 2) Flow forces 3) Impact forces (impacts between moving concrete blocks)......The following types of forces contribute to the stresses in a Dolos in a pack exposed to waves: 1)Gravity forces Compaction forces (mainly due to settlements, gravity and flow forces) 2) Flow forces 3) Impact forces (impacts between moving concrete blocks)...

  7. 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)

  8. Stressed podocytes

    DEFF Research Database (Denmark)

    Svenningsen, Per

    2015-01-01

    conditions and in response to injury induced by endoplasmatic reticulum (ER) stress (Golubinskaya et al., 2015). Their report shed light on the complex regulation of Best3 in podocytes and will help pave the way for future studies on the pathogenesis of kidneys diseases with podocyte injury. This article is...

  9. Stress Tests

    International Nuclear Information System (INIS)

    Our Nuclear Facilities have recently operated in a special regime. Since March until December they were scrutinised by a team verifying and drilling all possible scenarios in case of emergency situations, earthquake, floods or long-term power supply loss. Stress tests were the hard job but their findings are already now a great contribution. (author)

  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. 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

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

    International Nuclear Information System (INIS)

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

  13. 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.)

  14. 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 effects of the different peening treatments. Possible reasons for this are explored.

  15. Equi-penetration grazing incidence X-ray diffraction method: Stress depth profiling of ground silicon nitride

    International Nuclear Information System (INIS)

    In this work a new modification of the grazing incidence X-ray diffraction method for residual stress determination is presented. This equi-penetration grazing incidence X-ray diffraction method is especially suitable for the precise determination of the residual stress depth profile in materials. It originates from a sin2? approach based on the determination of the lattice spacing of various selected diffraction planes. Additionally, for each measurement the condition ??/?? = 0 is here fulfilled and one dataset corresponds strictly to a specific mean penetration depth ? independent of the tilt angle ?. This can be achieved by the individual adjustment of the incidence angle for each measured diffraction maximum. In the actual work, the influence of different surface finishes on the stress depth profile of commercial silicon nitride ceramic samples is investigated. The ground specimen displays an almost biaxial compressive stress parallel and near to the specimen surface of 3 GPa, which decreases almost up to zero in a depth of 5 ?m. After the polishing process, the specimens show a strongly reduced compressive stress maximum at the surface of 1 GPa, which diminishes similarly with increasing depth. The orientation between the stress component and the grinding direction is of minor influence. Furthermore, the influence of a possible residual stress component perpendicular to the sample surface is discussed

  16. Tensile strength and internal stress determination in salt compacts by diametrical and axial compression tests

    International Nuclear Information System (INIS)

    Due to the brittle character of the material an indirect method (diametrical and axial compression testing) was adopted for tensile strength determination. Two lots of compacts were prepared from salt powder, by pressing it in steel dyes by means of a hydraulic press. For uniaxial tests, cylindrical compacts were used. Biaxial tests were done on disk-shaped compacts, each disk having a diametrical V-shaped cut on one of its plane areas. The punches used for compression tests, were designed to obtain a ratio of 1.2 between their curvature radius and sample radius. At the same time with the tensile strength, the stress intensity factor (KIC and KIIC values) has been obtained. The results obtained are in good agreement with the mechanical properties of the salt, previously reported. (Authors)

  17. Stress hyperglycaemia

    OpenAIRE

    Dungan, Kathleen M; Braithwaite, Susan S; Preiser, Jean-Charles

    2009-01-01

    Results of randomised controlled trials of tight glycaemic control in hospital inpatients might vary with population and disease state. Individualised therapy for different hospital inpatient populations and identification of patients at risk of hyperglycaemia might be needed. One risk factor that has received much attention is the presence of pre-existing diabetes. So-called stress hyperglycaemia is usually defined as hyperglycaemia resolving spontaneously after dissipation of acute illness....

  18. BUCLASP 3: A computer program for stresses and buckling of heated composite stiffened panels and other structures, user's manual

    Science.gov (United States)

    Tripp, L. L.; Tamekuni, M.; Viswanathan, A. V.

    1973-01-01

    The use of the computer program BUCLASP3 is described. The code is intended for thermal stress and instability analyses of structures such as unidirectionally stiffened panels. There are two types of instability analyses that can be effected by PAINT; (1) thermal buckling, and (2) buckling due to a specified inplane biaxial loading. Any structure that has a constant cross section in one direction, that may be idealized as an assemblage of beam elements and laminated flat and curved plate strip-elements can be analyzed. The two parallel ends of the panel must be simply supported, whereas arbitrary elastic boundary conditions may be imposed along any one or both external longitudinal side. Any variation in the temperature rise (from ambient) through the cross section of a panel is considered in the analyses but it must be assumed that in the longitudinal direction the temperature field is constant. Load distributions for the externally applied inplane biaxial loads are similar in nature to the permissible temperature field.

  19. Stress and Mood

    Science.gov (United States)

    ... Relaxation Emotions & Relationships HealthyYouTXT Tools Home » Stress & Mood Stress & Mood Many people who go back to smoking ... story: Time Out Times 10 >> share What Causes Stress? Read full story: What Causes Stress? >> share The ...

  20. Fact Sheet on Stress

    Science.gov (United States)

    ... 2 items) Treatments (4 items) Fact Sheet on Stress Q&A on Stress for Adults: How it affects your health and ... to avoid more serious health effects. What is stress? Stress can be defined as the brain's response ...

  1. Stress and your heart

    Science.gov (United States)

    Coronary heart disease - stress; Coronary artery disease - stress ... Your body responds to stress on many levels. First, it releases stress hormones that make you breathe faster. Your blood pressure goes up. Your muscles ...

  2. Repetitive Stress Injuries

    Science.gov (United States)

    ... Can I Help a Friend Who Cuts? Repetitive Stress Injuries KidsHealth > For Teens > Repetitive Stress Injuries Print ... t had any problems since. What Are Repetitive Stress Injuries? Repetitive stress injuries (RSIs) are injuries that ...

  3. Stress and Infertility

    Science.gov (United States)

    ... the American Society for Reproductive Medicine Stress and infertility It is not clear how exactly stress impacts ... How can stress impact a fertility patient? Sometimes, infertility patients respond to the stress of being unable ...

  4. Stress and Pregnancy

    Science.gov (United States)

    ... Home > Pregnancy > Body & lifestyle changes > Stress and pregnancy Stress and pregnancy Now playing: E-mail to a ... at increased risk for health problems. What causes stress during pregnancy? The causes of stress are different ...

  5. Oxidative stress

    Directory of Open Access Journals (Sweden)

    Stevanović Jelka

    2012-01-01

    Full Text Available The unceasing need for oxygen is in contradiction to the fact that it is in fact toxic to mammals. Namely, its monovalent reduction can have as a consequence the production of short-living, chemically very active free radicals and certain non-radical agents (nitrogen-oxide, superoxide-anion-radicals, hydroxyl radicals, peroxyl radicals, singlet oxygen, peroxynitrite, hydrogen peroxide, hypochlorous acid, and others. There is no doubt that they have numerous positive roles, but when their production is stepped up to such an extent that the organism cannot eliminate them with its antioxidants (superoxide-dismutase, glutathione-peroxidase, catalase, transferrin, ceruloplasmin, reduced glutathion, and others, a series of disorders is developed that are jointly called „oxidative stress.“ The reactive oxygen species which characterize oxidative stress are capable of attacking all main classes of biological macromolecules, actually proteins, DNA and RNA molecules, and in particular lipids. The free radicals influence lipid peroxidation in cellular membranes, oxidative damage to DNA and RNA molecules, the development of genetic mutations, fragmentation, and the altered function of various protein molecules. All of this results in the following consequences: disrupted permeability of cellular membranes, disrupted cellular signalization and ion homeostasis, reduced or loss of function of damaged proteins, and similar. That is why the free radicals that are released during oxidative stress are considered pathogenic agents of numerous diseases and ageing. The type of damage that will occur, and when it will take place, depends on the nature of the free radicals, their site of action and their source. [Projekat Ministarstva nauke Republike Srbije, br. 173034, br. 175061 i br. 31085

  6. 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

    OpenAIRE

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

    2014-01-01

    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...

  7. 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)

  8. Stress, texture and microstructure of zirconium thin films probed by X-ray diffraction

    International Nuclear Information System (INIS)

    Zirconium (?-Zr) thin films (thicknesses: 12 nm-240 nm) have been deposited on glass substrates by dc magnetron sputtering. Anisotropic broadening of diffraction lines has been observed for all films when probed by X-ray diffraction. Williamson-Hall method of X-ray line profile analysis shows average crystallite sizes of a few nanometers and high average microstrains for all films. Diffraction stress analysis of Zr films reveals relatively high biaxial compressive stresses that are found to decrease with increasing film thickness. The level of stress has been compared to the theoretical yield strength of Zr films obtained by a model calculation. All Zr films show (0002) fiber texture as dominant texture component except 240 nm thick films. Ratios of strain-free lattice parameters (co/ao) determined for all Zr films are higher than the reported co/ao ratio for bulk zirconium. Observation of anisotropic diffraction line broadening in the textured Zr films with high in-plane compressive stress indicates anisotropy in the shape of individual crystallite in all films

  9. Shakedown criterion employing actual residual stress field and its application in numerical shakedown analysis

    Science.gov (United States)

    Zou, Zongyuan; Guo, Baofeng; Li, Yinxiao; Jin, Miao; Zhao, Shiyan

    2015-09-01

    Construction of the static admissible residual stress field and searching the optimal field are key tasks in the shakedown analysis methods applying the static theorem. These methods always meet dimension obstacles when dealing with complex problems. In this paper, a novel shakedown criterion is proposed employing actual residual stress field based on the static shakedown theorem. The actual residual stress field used here is produced under a specified load path, which is a sequence of proportional loading and unloading from zero to all the vertices of the given load domain. This ensures that the shakedown behavior in the whole load domain can be determined based on the theorem proposed by König. The shakedown criterion is then implemented in numerical shakedown analysis. The actual residual stress fields are calculated by incremental finite element elastic-plastic analysis technique for finite deformation under the specified load path with different load levels. The shakedown behavior and the shakedown limit load are determined according to the proposed criterion. The validation of the criterion is performed by a benchmark shakedown example, which is a square plate with a central hole under biaxial loading. The results are consistent with existing results in the literatures and are validated by full cyclic elastic-plastic finite element analysis. The numerical shakedown analysis applying the proposed criterion avoids processing dimension obstacles and performing full cyclic elastic-plastic analysis under arbitrary load paths which should be accounted for appearing. The effect of material model and geometric changes on shakedown behavior can be considered conveniently.

  10. Vibration and Stability of Thick Simply Supported Shallow Shells Subjected to In-Plane Stresses

    Science.gov (United States)

    MATSUNAGA, H.

    1999-08-01

    The effects of higher order deformations on natural frequencies and buckling stresses of a thick shallow shell with reactangular planform subjected to uniaxial and biaxial in-plane stresses are studied. Based on the power series expansion of displacement components, a set of fundamental dynamic equations of a two-dimensional higher order shallow shell theory is derived through Hamilton's principle. Several sets of truncated approximate theories which can take into account the complete effects of higher order deformations such as shear deformations with thickness changes and rotatory inertia are applied to solve the vibration and stability problems of a thick shallow shell. Three types of simply supported shallow shells with positive, zero and negative Gaussian curvatures are considered. In order to assure the accuracy of the present theory, convergence properties of the lowest two natural frequencies for the first vibration moder=s=1 are examined in detail. The present results are also compared with those of existing theories. In the case of a simply supported shallow shell, buckling stresses can be calculated from the natural frequencies without in-plane stresses.

  11. The influence of multiaxial states of stress on the hydrogen embrittlement of zirconium alloy sheet

    Science.gov (United States)

    Yunchang, Fan; Koss, D. A.

    1985-04-01

    The ductility of ZIRCALOY *-2 sheets containing 21-615 wt ppm hydrogen has been investigated at room temperature over a range of stress states from uniaxial to equibiaxial tension. Data based on locally determined fracture strains show a decrease in ductility with both increasing hydrogen content and increasing degree of biaxiality of the stress state. Metallographic and fractographic examinations indicate that the embrittlement is a consequence of void nucleation (due to hydride fracture), void growth, and void link-up. The influence of hydrogen content and stress state on each of the sequential stages of ductile fracture is determined. These results indicate that the primary cause for the influence of stress state on the hydrogen embrittlement of the ZIRCALOY sheet is that void link-up is initiated at a much lower critical void density in equibiaxial tension than in uniaxial tension. This appears to be a result of equibiaxial deformation enhancing (a) direct participation of previously unfractured hydrides in providing a fracture path linking up voids and (b) a localized shear instability process which is triggered by the nucleation of voids.

  12. Effect of Zirconia Thickness on the Tensile Stress of Zirconia Based All-Ceramic Restorations

    Directory of Open Access Journals (Sweden)

    Masood Shiezadeh

    2015-09-01

    Full Text Available Introduction: The purpose of the presented study was to evaluate the effect of zirconia thickness on the tensile stress of zirconia based all-ceramic restorations. Methods: Twenty zirconia disks with 10mm diameter were prepared in two groups using CAD/CAM system. The thickness of zirconia was 0.5mm in first group and 0.3mm in second group. After sintering, 0.4mm glass ceramic porcelain was applied to each disk. Then, sintering and glazing of porcelain carried out. Instron testing machine with 1mm/min crosshead speed used to evaluate the failure load of the samples. Biaxial Flexural strength standard formula employed to calculate tensile stress of specimens. Statistical analysis performed using SPSS software. Results: Although data analysis showed more maximum tensile stress in 1st group, no significant differences were found between two groups. Conclusion: Zirconia with 0.5mm and 0.3mm thicknesses cause similar tensile stress in all-ceramic restorations and thickness of these laminates could be reduced to 0.7mm.

  13. Stress assessment in piping under synthetic thermal loads emulating turbulent fluid mixing

    International Nuclear Information System (INIS)

    Highlights: • Generation of complex space-continuous and time-dependent temperature fields. • 1D and 3D thermo-mechanical analyses of pipes under complex surface thermal loads. • Surface temperatures and stress fluctuations are highly linearly correlated. • 1D and 3D results agree for a wide range of Fourier and Biot numbers. • Global thermo-mechanical loading promotes non-equibiaxial stress state. - Abstract: Thermal fatigue assessment of pipes due to turbulent fluid mixing in T-junctions is a rather difficult task because of the existing uncertainties and variability of induced thermal stresses. In these cases, thermal stresses arise on three-dimensional pipe structures due to complex thermal loads, known as thermal striping, acting at the fluid-wall interface. A recently developed approach for the generation of space-continuous and time-dependent temperature fields has been employed in this paper to reproduce fluid temperature fields of a case study from the literature. The paper aims to deliver a detailed study of the three-dimensional structural response of piping under the complex thermal loads arising in fluid mixing in T-junctions. Results of three-dimensional thermo-mechanical analyses show that fluctuations of surface temperatures and stresses are highly linearly correlated. Also, surface stress fluctuations, in axial and hoop directions, are almost equi-biaxial. These findings, representative on cross sections away from system boundaries, are moreover supported by the sensitivity analysis of Fourier and Biot numbers and by the comparison with standard one-dimensional analyses. Agreement between one- and three-dimensional results is found for a wide range of studied parameters. The study also comprises the effects of global thermo-mechanical loading on the surface stress state. Implemented mechanical boundary conditions develop more realistic overall system deformation and promote non-equibiaxial stresses

  14. Stress assessment in piping under synthetic thermal loads emulating turbulent fluid mixing

    Energy Technology Data Exchange (ETDEWEB)

    Costa Garrido, Oriol, E-mail: oriol.costa@ijs.si; El Shawish, Samir, E-mail: samir.elshawish@ijs.si; Cizelj, Leon, E-mail: leon.cizelj@ijs.si

    2015-03-15

    Highlights: • Generation of complex space-continuous and time-dependent temperature fields. • 1D and 3D thermo-mechanical analyses of pipes under complex surface thermal loads. • Surface temperatures and stress fluctuations are highly linearly correlated. • 1D and 3D results agree for a wide range of Fourier and Biot numbers. • Global thermo-mechanical loading promotes non-equibiaxial stress state. - Abstract: Thermal fatigue assessment of pipes due to turbulent fluid mixing in T-junctions is a rather difficult task because of the existing uncertainties and variability of induced thermal stresses. In these cases, thermal stresses arise on three-dimensional pipe structures due to complex thermal loads, known as thermal striping, acting at the fluid-wall interface. A recently developed approach for the generation of space-continuous and time-dependent temperature fields has been employed in this paper to reproduce fluid temperature fields of a case study from the literature. The paper aims to deliver a detailed study of the three-dimensional structural response of piping under the complex thermal loads arising in fluid mixing in T-junctions. Results of three-dimensional thermo-mechanical analyses show that fluctuations of surface temperatures and stresses are highly linearly correlated. Also, surface stress fluctuations, in axial and hoop directions, are almost equi-biaxial. These findings, representative on cross sections away from system boundaries, are moreover supported by the sensitivity analysis of Fourier and Biot numbers and by the comparison with standard one-dimensional analyses. Agreement between one- and three-dimensional results is found for a wide range of studied parameters. The study also comprises the effects of global thermo-mechanical loading on the surface stress state. Implemented mechanical boundary conditions develop more realistic overall system deformation and promote non-equibiaxial stresses.

  15. 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.)

  16. Wettability and optical properties of O{sub 2} and CF{sub 4} plasma treated biaxially oriented semicrystalline poly(ethylene terephthalate) films

    Energy Technology Data Exchange (ETDEWEB)

    Jucius, D., E-mail: dalius.jucius@ktu.lt [Institute of Materials Science, Kaunas University of Technology, Savanoriu 271, LT-50131 Kaunas (Lithuania); Grigaliunas, V.; Kopustinskas, V.; Lazauskas, A.; Guobiene, A. [Institute of Materials Science, Kaunas University of Technology, Savanoriu 271, LT-50131 Kaunas (Lithuania)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer PET films were treated by low pressure O{sub 2} and CF{sub 4} plasma. Black-Right-Pointing-Pointer Influence of the plasma treatment on optical properties and wettability was examined. Black-Right-Pointing-Pointer Aging effects were analyzed by storing the samples at room conditions for 60 days. Black-Right-Pointing-Pointer Highly hydrophilic surfaces were made without worsening of optical transmission. - Abstract: Influence of low pressure O{sub 2}, CF{sub 4}, and successive O{sub 2} and CF{sub 4} RF plasma treatment on optical properties and wettability of biaxially oriented semicrystalline poly(ethylene terephthalate) (PET) was examined. Produced by industrial stretch-blow molding PET films of the 300 {mu}m thickness were chosen for the experiments. Influence of the aging was also investigated by storing plasma treated samples at room conditions for 60 days. It was revealed that O{sub 2} plasma treated samples suffered from the hydrophobic recovery and long term improvement of hydrophilicity was only a moderate. Energetic CF{sub 4} plasma treatment was able to form a large number of surface active sites which in turn was capable to attach the oxygen containing groups and to increase the hydrophilicity. However, aged for 10-60 days CF{sub 4} plasma treated PET films have showed a large scattering of the contact angle values measured on the same surface. Successive O{sub 2} and CF{sub 4} plasma treatment, despite induced hydrophobicity of as treated films, after 3 days of aging have resulted in highly homogeneous hydrophilic ({Theta} Almost-Equal-To 20 Degree-Sign ) surfaces which have retained their hydrophilicity for the entire period of investigation. Moreover, combined plasma treatment of PET films has not influenced significantly the transmission of visible light. So, such a treatment can be considered as beneficial for the production of highly homogeneous hydrophilic surfaces without significant influence on their optical properties.

  17. 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...

  18. 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

  19. How Coaches Manage Stress.

    Science.gov (United States)

    Ruder, M. Karen

    1991-01-01

    Presents stress management strategies for coaches, focusing on what stress is, how it affects the body, and what to do to minimize the effects of stress on health. The article explains on- and off-the-job stress factors so coaches can recognize potential stress situations and handle them as they occur. (SM)

  20. 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.