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1

Biaxial stress effects on magnetization perpendicular to the stress plane  

Energy Technology Data Exchange (ETDEWEB)

Effects of biaxial stress in steel on magnetization in a direction normal to the stress plane were investigated both theoretically and experimentally. The two results, which agreed qualitatively, showed that the magnetization in the normal direction generally decreased with the absolute value of the sum of the two principal stresses. The implication to nondestructive measurements of biaxial stress is discussed.

Sablik, M.J.; Kwun, H.; Burkhardt, G.L. [Southwest Research Inst., San Antonio, TX (United States); Langman, R.A. [Univ. of Tasmania, Hobart, Tasmania (Australia)

1995-11-01

2

Analysis of Biaxially Stressed Bridge Deck Plates  

DEFF Research Database (Denmark)

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.

Jönsson, Jeppe; Bondum, Tommi HØjer

2012-01-01

3

Fatigue crack propagation of magnesium alloy in biaxial stress fields  

Science.gov (United States)

Fatigue crack propagation tests of magnesium alloy were conducted under conditions of biaxial and uniaxial loading by using a cruciform specimen in a biaxial fatigue machine, in order to investigate the effect of non-singular stress cycling on the fatigue crack growth properties ?KI -da/dN. The Magnesium alloys (AZ31B-O) used for this research are 2.5mm thickness plates. There are four different kinds of plates due to their heat treatment conditions. These conditions are (a) with no heat treatments (AZ31B-O), (b) 200-degree 2 hours (AZ31B-200), (c) 350-degree 2 hours (AZ31B-350), and (d) 430-degree 2 hours (AZ31B-430). From these comprehensive experiments, the remarkable effect was found in the specific biaxial load stress ratio ?x0/?y0 on ?KI -da/dN relation. When biaxial load stress ratio was 0.5, it turned out that the fatigue crack propagation rate of a magnesium alloy becomes very slow. Of course, in other biaxial load stress ratios, fatigue crack propagation velocity was influenced to some extent. It turned out that fatigue crack propagation rate becomes fast when a biaxial load stress ratio is minus, and it becomes slow when a biaxial load stress ratio is plus. Some discussion is made on the effect of microstructure on fatigue crack propagation of magnesium alloy in a biaxial stress field.

Itoh, Yasumi; Shimamoto, Akira

2005-05-01

4

The influence of biaxial stresses on the failure assessment curve  

Energy Technology Data Exchange (ETDEWEB)

In this paper, the influence of biaxial stresses on the crack/notch failure assessment curve (FAC) has been explored by means of incremental theory elastic-plastic finite element (EPFE) method. The FACs of different ratio of biaxial stresses have been established based on the J-integral calculation of center cracked and notched specimens. Meanwhile the comparisons have been made between the FACs given by EPFE and CEGB R6 Option 2. It shows that the biaxial stresses at plastic stage have evident influence on FACs, but the safety range of the FACs are close to that of uniaxial stress FAC. With the standpoint of view of engineering, the FAC given by R6 Option 2 under the uniaxial stress condition could roughly be used to the failure assessment of structures containing defects under biaxial stress condition, but for advanced or precise assessment, the biaxial stress effect must be taken into account. The influence of biaxial stresses on J-integral values and path independence has been investigated at the same time.

Wang, W.Q.; Li, A.J. [Qingdao Institute of Chemical Technology (China). Dept. of Mechanical Engineering; Ding, P.F. [Chinese Mechanical Engineering Society, Beijing (China)

1995-11-01

5

Effect of Increasing Speed on Stress of Biaxial Bogie Frames  

Directory of Open Access Journals (Sweden)

Full Text Available Increasing the trains’ speed has always been one of the goals of any railway industry and train manufacturers. Also, the influence of the train speed on bogie’s dynamics has an immense importance. Therefore, it is important to analyze the effect of train speed on the stress distribution in different parts of train structure. In this study the result of the increasing speed on the applied stresses of a biaxial bogie frame has been examined. For this purpose, a biaxial bogie frame has been modeled using finite element analysis. Static and dynamic forces applied on the bogie with biaxial frame have been obtained for different speeds and rail roughness. The Von Mises stresses are adopted as equivalent stresses in the strength calculation. The results show that maximum stress always has been induced in the bogie bowl also the increase in bogie’s speed has remarkable effect on the increment of applied stresses in the bogie frame.

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

2011-01-01

6

Stress Concentrations for Slotted Plates in Bi-Axial Stress  

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

7

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1993-01-31

8

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

International Nuclear Information System (INIS)

[en] 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

1993-01-01

9

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

Directory of Open Access Journals (Sweden)

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

Ono Yuichi; Li Cheng; Hino Daisuke

2010-01-01

10

Estimation of biaxial residual stress in welded steel tubes by Barkhausen noise measurements  

Energy Technology Data Exchange (ETDEWEB)

Relation between biaxial stress and Barkhausen noise was evaluated in mild steel specimens by biaxial bending experiments. Residual stresses of welded steel tubes were evaluated by Barkhausen noise and X-ray diffraction. Barkhausen noise values were converted into residual stress values by interpolation from reference measurements made by X-ray diffraction and Barkhausen noise. Residual stress values measured by both methods were consistent. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

Lindgren, M.; Lepistoe, T. [Institute of Materials Science,Tampere University of Technology, P.O.Box 589,33101 Tampere (Finland)

2002-08-01

11

Application of hysteresis modeling to magnetic techniques for monitoring biaxial stress  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1993-12-31

12

Application of hysteresis modeling to magnetic techniques for monitoring biaxial stress  

International Nuclear Information System (INIS)

[en] 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 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 predicts, 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

1993-01-01

13

A preliminary numerical stress analysis of a dynamic biaxial testing machine  

International Nuclear Information System (INIS)

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

1983-01-01

14

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

Directory of Open Access Journals (Sweden)

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.

R. K. Bhagat; V. K. Singh; P. C. Gope; A.K. Chaudhary

2012-01-01

15

Application of magnetomechanical hysteresis modeling of magnetic techniques for monitoring neutron embrittlement and biaxial stress. Second year interim report, June 1992--December 1992  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1993-01-31

16

Effect of Increasing Speed on Stress of Biaxial Bogie Frames  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Increasing the trains’ speed has always been one of the goals of any railway industry and train manufacturers. Also, the influence of the train speed on bogie’s dynamics has an immense importance. Therefore, it is important to analyze the effect of train speed on the stress distribution in different...

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

17

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

Science.gov (United States)

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

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

2013-09-01

18

Large enhancement of boron solubility in silicon due to biaxial stress  

International Nuclear Information System (INIS)

[en] One of the important challenges to the semiconductor industry today is to enhance the solid solubility of several dopants, boron in particular, in silicon. We calculate the equilibrium solid solubility of boron in Si from first principles and examine the effect of biaxial stress. We find an unexpectedly large enhancement, on the order of 150 percent, for only 1 percent strain primarily due to the charge of the substitutional boron impurity in Si. We point out that this effect is an intrinsic property of Si and is expected to be important for other dopants as well

2002-02-01

19

Large enhancement of boron solubility in silicon due to biaxial stress  

Energy Technology Data Exchange (ETDEWEB)

One of the important challenges to the semiconductor industry today is to enhance the solid solubility of several dopants, boron in particular, in silicon. We calculate the equilibrium solid solubility of boron in Si from first principles and examine the effect of biaxial stress. We find an unexpectedly large enhancement, on the order of 150 percent, for only 1 percent strain primarily due to the charge of the substitutional boron impurity in Si. We point out that this effect is an intrinsic property of Si and is expected to be important for other dopants as well.

Sadigh, Babak; Lenosky, Thomas J.; Caturla, Maria-Joaw; Quong, Andrew A.; Benedict, Lorin X.; Diaz de la Rubia, Tomas; Giles, Martin M.; Foad, Majeed; Spataru, Catalin D.; Louie, Steven G.

2002-02-01

20

Large enhancement of boron solubility in silicon due to biaxial stress  

CERN Multimedia

One of the important challenges to the semiconductor industry today is to enhance the solid solubility of several dopants, boron in particular, in silicon. We calculate the equilibrium solid solubility of boron in Si from first principles and examine the effect of biaxial stress. We find an unexpectedly large enhancement, on the order of 150 percent, for only 1 percent strain primarily due to the charge of the substitutional boron impurity in Si. We point out that this effect is an intrinsic property of Si and is expected to be important for other dopants as well.

Sadigh, B; Caturla, M J; Quong, A A; Benedict, L X; Díaz de la Rubia, T; Giles, M M; Foad, M; Spataru, C D; Louie, S G

2002-01-01

 
 
 
 
21

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

Energy Technology Data Exchange (ETDEWEB)

Objective of this project is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. If neutron embrittlement and biaxial stress can be measured via changes in magnetic properties, this should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. This first-year report addresses the issue of using magnetic property changes to detect neutron embrittlement. The magnetic measurements were all done on irradiated specimens previously broken in two in a Charpy test to determine their embrittlement. The magnetic properties of the broken charpy specimens from D.C. Cook did not correlate well with fluence or embrittlement parameters, possible due to metallurgical reasons. correlation was better with Indian Point 2 specimens, with the nonlinear harmonic amplitudes showing the best correlation (R[sup 2][approximately]0.7). However, correlation was not good enough. It is recommended that tests be done on unbroken irradiated Charpy specimens, for which magnetic characterization data prior to irradiation is available, if possible.

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

1993-01-31

22

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)

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.

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

1999-08-01

23

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

International Nuclear Information System (INIS)

[en] 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

1992-01-01

24

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1992-01-01

25

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-07-01

26

Stress and strain in rat pulmonary artery material during a biaxial bubble test.  

Science.gov (United States)

A biaxial bubble test has been designed to ascertain the mechanical properties of rat pulmonary arteries. The analytical procedure used to estimate stress and strain from the resulting test data is presented along with some analytical results. The bubble test was performed by loading a flat piece of rat pulmonary artery into a test fixture beneath a circular opening; the material was subsequently pressurized from below, producing a "bubble" of deformed material. Due to the anisotropy of the rat pulmonary artery, the resulting bubble was ellipsoidal in shape. Test results were recorded in the form of side-view images taken from various angles at incremental values of pressure. Average strains were estimated with the use of image analysis to measure changes in the bubble perimeter during inflation. Formulations for isotropic materials were applied to estimate stresses based on the anisotropic geometry of the bubbles produced during testing; some results of this preliminary analysis are presented here. Results from this analysis show differences in mechanical properties of the rat pulmonary artery from those of healthy versus hypertensive rats. PMID:15133975

Wright, Joyce E; Drexler, Elizabeth S; Slifka, Andrew J; McCowan, Christopher N; Ivy, Dunbar D; Shandas, Robin

2004-01-01

27

Stress and strain in rat pulmonary artery material during a biaxial bubble test.  

UK PubMed Central (United Kingdom)

A biaxial bubble test has been designed to ascertain the mechanical properties of rat pulmonary arteries. The analytical procedure used to estimate stress and strain from the resulting test data is presented along with some analytical results. The bubble test was performed by loading a flat piece of rat pulmonary artery into a test fixture beneath a circular opening; the material was subsequently pressurized from below, producing a "bubble" of deformed material. Due to the anisotropy of the rat pulmonary artery, the resulting bubble was ellipsoidal in shape. Test results were recorded in the form of side-view images taken from various angles at incremental values of pressure. Average strains were estimated with the use of image analysis to measure changes in the bubble perimeter during inflation. Formulations for isotropic materials were applied to estimate stresses based on the anisotropic geometry of the bubbles produced during testing; some results of this preliminary analysis are presented here. Results from this analysis show differences in mechanical properties of the rat pulmonary artery from those of healthy versus hypertensive rats.

Wright JE; Drexler ES; Slifka AJ; McCowan CN; Ivy DD; Shandas R

2004-01-01

28

Magnetic flux leakage inspection of gas pipelines: The effects of biaxial stress. Topical report, April 1993-September 1995  

Energy Technology Data Exchange (ETDEWEB)

The project is one component of the GRI program, `Characterization of Magnetic Flux Leakage (MFL) Indications Found During In-Line Inspection of Natural Gas Transmission Pipelines.` The objective of the greater project was to investigate the effects of pipeline parameters and MFL inspection variables on corrosion, defect characterization. The work at SwRI, the subject of this report, concerns the effect of biaxial pipe wall stress.

Crouch, A.E.; Beissner, R.E.; Burkhardt, G.L.; Creek, E.A.; Grant, T.S.

1996-03-01

29

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

International Nuclear Information System (INIS)

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

2010-01-01

30

Electromigration-driven complex dynamics of void surfaces in stressed metallic thin films under a general biaxial mechanical loading  

Science.gov (United States)

We report results of a systematic computational study of the electromigration-driven complex surface dynamics of voids in mechanically stressed thin films of face-centered cubic metals with -oriented film planes. The films are subjected to an external electric field simultaneously with biaxial mechanical loading, which can be either purely compressive, ranging from purely isotropic to strongly anisotropic including uniaxial, or a mixed type of loading with both tensile and compressive stress components in the applied stress tensor. Our analysis is based on self-consistent dynamical simulations of driven void surface morphological evolution following a well validated, two-dimensional, and fully nonlinear model. We find that depending on the electromechanical conditions, void size, and surface diffusional anisotropy, two types of asymptotic states can be stabilized in the void surface dynamical response, namely, morphologically steady or time-periodic traveling voids, and film failure can be caused by void tip extension. The loading mode as well as the loading anisotropy are found to be the significant factors in determining the void morphological stability domains and can be tailored to stabilize steady or time-periodic states and to increase the film's resistance to failure. Under a mixed (tensile + compressive) loading mode, we find that it is impossible to stabilize steady states in the void morphological response and that the stress levels that the film can sustain prior to failure are much lower than those under purely tensile or purely compressive biaxial loading.

Dasgupta, Dwaipayan; Sfyris, Georgios I.; Maroudas, Dimitrios

2012-10-01

31

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

Energy Technology Data Exchange (ETDEWEB)

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.

Bass, B.R.; Bryson, J.W.; Mcafee, W.J.; Pennell, W.E.; Theiss, T.J.

1993-06-01

32

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

1993-01-01

33

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1992-04-01

34

Influence of biaxial stress on the magnetic properties of cobalt nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-07-01

35

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.

1981-08-21

36

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

2007-01-01

37

Application of magnetomechanical hysteresis modeling of magnetic techniques for monitoring neutron embrittlement and biaxial stress. First year report, June 1991--June 1992  

Energy Technology Data Exchange (ETDEWEB)

Objective of this project is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. If neutron embrittlement and biaxial stress can be measured via changes in magnetic properties, this should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. This first-year report addresses the issue of using magnetic property changes to detect neutron embrittlement. The magnetic measurements were all done on irradiated specimens previously broken in two in a Charpy test to determine their embrittlement. The magnetic properties of the broken charpy specimens from D.C. Cook did not correlate well with fluence or embrittlement parameters, possible due to metallurgical reasons. correlation was better with Indian Point 2 specimens, with the nonlinear harmonic amplitudes showing the best correlation (R{sup 2}{approximately}0.7). However, correlation was not good enough. It is recommended that tests be done on unbroken irradiated Charpy specimens, for which magnetic characterization data prior to irradiation is available, if possible.

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

1993-01-31

38

Engineering piezoresistivity using biaxially strained silicon  

DEFF Research Database (Denmark)

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

Pedersen, Jesper Goor; Richter, Jacob

2008-01-01

39

Effect of simulated medium-Btu coal gasifier atmospheres on the biaxial stress rupture behavior of four candidate coal gasifier alloys  

Energy Technology Data Exchange (ETDEWEB)

Tests were conducted to determine whether the biaxial stress rupture behavior of four alloys was adversely affected by exposure to four simulated medium-Btu coal gasifier atmospheres. The results of exposures up to approximately 500 h at temperatures between 649 and 982/sup 0/C are presented. Exposure to these atmospheres at temperatures below 900/sup 0/C did not significantly reduce the rupture properties from those measured in air. Only at 982/sup 0/C were the rupture strength and life in the simulated coal gasifier atmospheres lower than those measured in air at atmospheric pressure. Possible reasons for this reduction in strength/life are discussed. The results of detailed examination of specimen ruptures are also presented.

Horton, R.M.; Smolik, G.R.

1982-01-01

40

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

Energy Technology Data Exchange (ETDEWEB)

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-A{sub 2} analytical model. The analytical model is based on the critical stress concept and takes into consideration the constraint effect using the second parameter A{sub 2} 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.

Chao, Yuh-Jin [Univ. of South Carolina, Columbia, SC (United States). Dept. of Mechanical Engineering; Lam, Poh-Sang [Westinghouse Savannah River Co., Aiken, SC (United States)

1995-02-01

 
 
 
 
41

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

1995-01-01

42

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1992-01-01

43

Evaluation of anisotropic effective stress-strain criteria for the biaxial yield and flow of 2024 aluminum tubes  

International Nuclear Information System (INIS)

[en] 2024 aluminum tubes, heat treated to a T6 and T8 temper, were tested in combinations of tension-internal pressure and tension-torsion loading. Yield loci and flow behavior were determined for both modes of loading and compared to theoretical predictions. Both tempers of 2024 aluminum exhibited crystallographic textures and anisotropic yield and flow. Hill's quadratic yield criterion and the associated flow rule under-estimate balanced biaxial yield and flow, which is consistent with hydraulic bulge data on other face-centered cubic metals. Hill's nonquadratic criterion, which adds one additional parameter, and Bassani's criterion, which adds two parameters, predict the anisotropic yield behavior much more accurately. Predictions of the complete flow behavior, including strain paths, with these anisotropic criteria could be improved markedly by including provisions for planar anisotropy

1983-01-01

44

Evaluation of anisotropic effective stress-strain criteria for the biaxial yield and flow of 2024 aluminum tubes  

Energy Technology Data Exchange (ETDEWEB)

2024 aluminum tubes, heat treated to a T6 and T8 temper, were tested in combinations of tension-internal pressure and tension-torsion loading. Yield loci and flow behavior were determined for both modes of loading and compared to theoretical predictions. Both tempers of 2024 aluminum exhibited crystallographic textures and anisotropic yield and flow. Hill's quadratic yield criterion and the associated flow rule under-estimate balanced biaxial yield and flow, which is consistent with hydraulic bulge data on other face-centered cubic metals. Hill's nonquadratic criterion, which adds one additional parameter, and Bassani's criterion, which adds two parameters, predict the anisotropic yield behavior much more accurately. Predictions of the complete flow behavior, including strain paths, with these anisotropic criteria could be improved markedly by including provisions for planar anisotropy.

Stout, M.G.; Hecker, S.S.; Bourcier, R.

1983-10-01

45

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.).

1976-01-01

46

Biaxial media revisited  

Science.gov (United States)

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

New, G. H. C.

2013-09-01

47

Testing techniques in dynamic biaxial loading  

International Nuclear Information System (INIS)

In order to investigate dynamic material properties under a biaxial state of stress, the following developments are presented: a cruciform specimen; a device activated by an electric motor for strain rates ranging between 10-4 and 10-1s-1; a hydropneumatic device for testing at strain rates ranging from 10-1 to 102s-1; and a high-load (5 MN) biaxial machine for testing large specimens at strain rates ranging from 10-4 to 103s-1. (author)

1979-03-30

48

Biaxial fatigue strength of a fine-grained isotropic graphite for HTTR  

International Nuclear Information System (INIS)

Biaxial fatigue tests on an isotropic graphite IG-11 used in the HTTR were done in the stress regimes of tension-tension and compression-tension at room temperature to evaluate its fatigue strength at the biaxial state. Biaxial fatigue tests at 1,273 K in a vacuum were also done in the latter stress regime. Applied stress levels in the longitudinal direction ranged from 75 to 90% of the mean static strength, and in the transverse direction, from 53 to 74% of the mean strength. It was indicated from the tests that (1) the difference in the fatigue strength between the uniaxial and biaxial was observed when the applied stress levels were smaller than about 90% of the mean strength, (2) the biaxial fatigue strength was found to be larger than that for the uniaxial if the biaxial applied stresses were normalized to the mean biaxial static strength, (3) the biaxial fatigue strength at 1,273 K was equal to or larger than that at room temperature, (4) the evaluation of the integrity of graphite components in the HTTR, from the aspect of the biaxial fatigue, was believed to be conservative on the basis of the uniaxial fatigue strength and the biaxial static strength. (author)

1998-01-01

49

Biaxial strength of HY 80 steel  

Energy Technology Data Exchange (ETDEWEB)

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

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

1985-04-01

50

Biaxial yield surface investigation of polymer-matrix composites.  

UK PubMed Central (United Kingdom)

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

Ye J; Qiu Y; Zhai Z; He Z

2013-01-01

51

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

International Nuclear Information System (INIS)

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

2008-01-01

52

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

Science.gov (United States)

Cruciform beam fracture mechanics specimens 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 biaxal bending stress component in the test se...

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

1999-01-01

53

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.

2006-01-01

54

Structures having enhanced biaxial texture  

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-01-01

55

Structures having enhanced biaxial texture  

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-09-28

56

Biaxial vasoactivity of porcine coronary artery.  

UK PubMed Central (United Kingdom)

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 relationship in circumferential and axial directions. Based on the measurements, a biaxial active strain energy function is proposed to quantify the constitutive stress-strain relationship in the physiological range of loading. The strain energy is expressed as a Gauss error function in the physiological pressure range. In K(+)-induced vasoconstriction, the mean ± SE values of outer diameters at transmural pressure of 80 mmHg were 3.41 ± 0.17 and 3.28 ± 0.24 mm at axial stretch ratios of 1.3 and 1.5, respectively, which were significantly smaller than those in Ca(2+)-free-induced vasodilated state (i.e., 4.01 ± 0.16 and 3.75 ± 0.20 mm, respectively). The mean ± SE values of the inner and outer diameters in no-load state and the opening angles in zero-stress state were 1.69 ± 0.04 mm and 2.25 ± 0.08 mm and 126 ± 22°, respectively. The active stresses have a maximal value at the passive pressure of 80-100 mmHg and at the active pressure of 140-160 mmHg. Moreover, a mechanical analysis shows a significant reduction of mean stress and strain (averaged through the vessel wall). These findings have important implications for understanding SMC mechanics.

Huo Y; Cheng Y; Zhao X; Lu X; Kassab GS

2012-05-01

57

Biaxial Fatigue Cracking from Notch.  

Science.gov (United States)

A study was initiated to clarify the behavior of biaxial fatigue cracking from a notch, transverse or 45 deg inclined, in a cruciform specimen of a 7075-T651 aluminum alloy. The biaxial fatigue test was conducted in air and aqueous 3.5% NaCl solution at r...

B. A. Pregger C. Lei E. U. Lee R. E. Taylor

2013-01-01

58

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.)

1999-01-01

59

Biaxial vent extruder  

Energy Technology Data Exchange (ETDEWEB)

A biaxial vent extruder is described for processing of slurry-like waste fluids or radioactive waste fluids which have a hopper cylinger, a solidifying substance port and a solidified substance port. A plurality of vent cylinders each having a vent port are provided with a plunger type scraper. An extruding cylinder having a single opening for a main screw is connected to the assembled vent cylinders. The main screw extends to the upstream end of the extruding cylinder and a sub-screw extends to the extruding cylinder. The screws each having a full flight engaging the other and a set of rings are mounted on the screws near the respective vent port inlets. The screws are rotated in different directions and inwardly with respect to the vent ports. Rotors may be mounted on the screws to break down solid particles.

Idemoto, A.; Maki, Y.; Oda, N.

1981-04-07

60

Biaxial vent extruder  

International Nuclear Information System (INIS)

[en] A biaxial vent extruder is described for processing of slurry-like waste fluids or radioactive waste fluids which have a hopper cylinger, a solidifying substance port and a solidified substance port. A plurality of vent cylinders each having a vent port are provided with a plunger type scraper. An extruding cylinder having a single opening for a main screw is connected to the assembled vent cylinders. The main screw extends to the upstream end of the extruding cylinder and a sub-screw extends to the extruding cylinder. The screws each having a full flight engaging the other and a set of rings are mounted on the screws near the respective vent port inlets. The screws are rotated in different directions and inwardly with respect to the vent ports. Rotors may be mounted on the screws to break down solid particles

1981-01-01

 
 
 
 
61

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

DEFF Research Database (Denmark)

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

Jönsson, Jeppe; Bondum, T. H.

2012-01-01

62

Influence of irradiation, load history, and stress bi-axiality on initiation and propagation of stress corrosion cracks induced by iodine in zirconium alloys; Influence de l'irradiation, de l'historique de chargement et de la biaxialite des contraintes sur l'amorcage et le debut de la propagation des fissures de corrosion sous contrainte par l'iode des alliages de zirconium  

Energy Technology Data Exchange (ETDEWEB)

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

Mozzani, N.; Auzoux, Q.; Le Boulch, D. [CEA Saclay, DEN, SEMI, 91 - Gif-sur-Yvette (France); Andrieu, E.; Blanc, Ch. [Universite de Toulouse, CIRIMAT, UPS/CNRS/INPT, ENSIACET, 31 - Toulouse (France); Trocellier, P. [CEA Saclay, DEN, SRMP, 91 - Gif-sur-Yvette (France)

2010-03-15

63

Methodology for dynamic biaxial tension testing of pregnant uterine tissue.  

Science.gov (United States)

Placental abruption accounts for 50% to 70% of fetal losses in motor vehicle crashes. Since automobile crashes are the leading cause of traumatic fetal injury mortality in the United States, research of this injury mechanism is important. Before research can adequately evaluate current and future restraint designs, a detailed model of the pregnant uterine tissues is necessary. The purpose of this study is to develop a methodology for testing the pregnant uterus in biaxial tension at a rate normally seen in a motor vehicle crash. Since the majority of previous biaxial work has established methods for quasi-static testing, this paper combines previous research and new methods to develop a custom designed system to strain the tissue at a dynamic rate. Load cells and optical markers are used for calculating stress strain curves of the perpendicular loading axes. Results for this methodology show images of a tissue specimen loaded and a finite verification of the optical strain measurement. The biaxial test system dynamically pulls the tissue to failure with synchronous motion of four tissue grips that are rigidly coupled to the tissue specimen. The test device models in situ loading conditions of the pregnant uterus and overcomes previous limitations of biaxial testing. A non-contact method of measuring strains combined with data reduction to resolve the stresses in two directions provides the information necessary to develop a three dimensional constitutive model of the material. Moreover, future research can apply this method to other soft tissues with similar in situ loading conditions. PMID:17487086

Manoogian, Sarah; Mcnally, Craig; Calloway, Britt; Duma, Stefan

2007-01-01

64

Crack opening/closing behaviors under biaxial cyclic loadings in carbon steel  

Energy Technology Data Exchange (ETDEWEB)

The crack opening/closing behaviors were calculated for the cruciform specimen with through-thickness pre-crack, which is subjected to biaxial cyclic loadings at various biaxial stress ratios, by means of three dimensional elastic-plastic finite element method. The calculation showed the followings: The crack opening displacement increases as biaxial stress ratio decreases under the cyclic loadings at the biaxial ratios in the range of -1.0

Hatanaka, K.; Ogawa, H. [Ube National Coll. of Technology (Japan); Ohgi, J. [Yamaguchi Univ. (Japan); Fujiwara, F. [KUBOTA Corp. (Japan)

2003-07-01

65

Correlation of uniaxial and biaxial fracture strengths of ceramics  

Energy Technology Data Exchange (ETDEWEB)

The increased utilization of brittle materials in structural applications has necessitated a need for better understanding of factors governing fracture strengths in multiaxial stress states. The research on which this paper is based examines the problem of relating fracture strengths of ceramics in biaxial stress states to strengths in uniaxial stress states. The problem is divided into two parts: in the first part fracture criteria for failure of brittle materials from single flaws are evaluated through controlled-flaw experiments in different stress states and fracture mechanics theory. The derived fracture criteria are then employed in a statistical fracture theory framework to predict strengths of ceramics failing from surface flaws.

Shetty, D.K.; Petrovic, J.J.; Rosenfield, A.R.; Duckworth, W.H.

1984-01-01

66

Control of fatigue crack propagation and estimation of closing effect under biaxial loading; Fissures de fatigue sous chargement biaxial. Controle de la propagation des fissures et evaluation de l`effet de fermeture  

Energy Technology Data Exchange (ETDEWEB)

The integrity of mechanical components subjected to fatigue can be strongly influenced by the biaxial loading system, residual stress fields, and several other factors. This paper deals with fatigue crack propagation under biaxial loading. The design and preliminary development of a biaxial fatigue testing facility is described for studying high-cycle low-strain fatigue. The concept of crack closure induced by plasticity, introduced by Elber, is important when crack faces remain locked under cyclic loading even loading even though the crack is subjected to loading in mode I. Within this study, tests were conducted on a 2 mm thick standard specimen with a cruciform geometry, and involving two loading modes {lambda}= O and {lambda}=1, where {lambda} is the bi-axiality parameter {sigma}{sub x}/{sigma}{sub y}. The material used is the aluminium alloy 1030. A life prediction methodology for fatigue crack propagation under biaxial loading loading is presented (authors) 9 refs.

Jendoubi, K. [ESST de Tunis, (Tunisia). Dept. Genie Mecanique; Hamza, S. [INSAT de Tunis (Tunisia). Dept. Genie Physique et Instrumentation

1998-03-01

67

Biaxially textured articles formed by plastic deformation  

Energy Technology Data Exchange (ETDEWEB)

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

Goyal, Amit (Knoxville, TN)

2001-01-01

68

Biaxially oriented film on flexible polymeric substrate  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2009-10-13

69

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1998-06-01

70

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

1998-01-01

71

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1998-01-01

72

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

1998-01-01

73

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

1995-01-01

74

Biaxial loading effects on fracture toughness of reactor pressure vessel steel  

Energy Technology Data Exchange (ETDEWEB)

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 {approximately}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 {approximately}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.

McAfee, W.J.; Bass, B.R.; Bryson, J.W. Jr.; Pennell, W.E. [Oak Ridge National Lab., TN (United States)

1995-03-01

75

Buffer layers on biaxially textured metal substrates  

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-01-01

76

Field-Induced Rheology in Uniaxial and Biaxial Fields  

International Nuclear Information System (INIS)

[en] 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

1999-01-01

77

Biaxially corrugated flexible sheet material  

Energy Technology Data Exchange (ETDEWEB)

A flexible biaxially corrugated sheet material is formed from a plurality of identical trapezium segments which are arranged in a plurality of long strips a single segment wide. Adjacent strips are mirror images of each other and connected along adjoining sides with the angles of the four corners of adjacent segments being alternately less than 360.degree. and greater than 360.degree. along the length of a strip such that the sheet material has an undulating configuration, and is inherently curved and cannot lie in a flat plane.

Schmertz, John C. (5308 Ellsworth Ave., Pittsburgh, PA 15232)

1991-04-16

78

Peripheral shear strength of biaxially tensioned reinforced concrete wall elements  

Energy Technology Data Exchange (ETDEWEB)

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

White, R.N.; Gergely, P.; Jau, W.C. (Cornell Univ., Ithaca, NY (USA). Dept. of Structural Engineering)

1982-05-01

79

Peripheral shear strength of biaxially tensioned reinforced concrete wall elements  

International Nuclear Information System (INIS)

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

1981-08-21

80

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

Energy Technology Data Exchange (ETDEWEB)

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 {epsilon}-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.

Wada, M. [Department of Mechanical Engineering, Hosei University, Koganei, Tokyo 184-8584 (Japan)], E-mail: mwada_bb@ybb.ne.jp; Naoi, H. [Department of Mechanical Engineering, Hosei University, Koganei, Tokyo 184-8584 (Japan); Yasuda, H. [Department of Mechanical Engineering, Kobe University, Nada, Kobe 657-8501 (Japan); Maruyama, T. [Awaji Materia Co., Ltd. 2-3-13, Kanda-ogawamachi, Chiyoda, Tokyo 101-0052 (Japan)

2008-05-25

 
 
 
 
81

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.

2008-05-25

82

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

Science.gov (United States)

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 subjected to uniaxial or biaxial loading conditions are shown to represent a significant challenge for these methodologies. Unresolved issues identified from these analyses require resolution as part of a validation process for biaxial loading applications.

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

1993-11-01

83

Biaxially textured articles formed by powder metallurgy  

Energy Technology Data Exchange (ETDEWEB)

A biaxially textured alloy article comprises 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 ; compacted and heat treated, then rapidly recrystallized 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.

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

2001-01-01

84

Biaxial mechanical modeling of the small intestine.  

UK PubMed Central (United Kingdom)

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

Bellini C; Glass P; Sitti M; Di Martino ES

2011-11-01

85

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-01-15

86

Strength and Stiffness of Reinforced Concrete Columns under Biaxial Bending.  

Science.gov (United States)

The strength and stiffness behavior of reinforced concrete columns subjected to biaxial bending and compression was investigated. In order to provide data points on biaxial interaction surfaces, nine rectangular cross section columns and fifteen partial c...

V. Mavichak R. W. Furlong

1976-01-01

87

Effect of biaxiality on fracture behavior: testing and analysis of cruciform specimen  

International Nuclear Information System (INIS)

This paper presents the details of experimental and analytical studies carried out on the cruciform specimens. Cruciform specimens are widely used to study the effect of constraint on the fracture process. Reactor Safety Division, BARC has embarked upon the fracture tests on cruciform specimens to study this effect. Six Cruciform specimens with part through crack at the core have been tested under bending at CSIR-SERC, Chennai. Fracture tests have been carried out on three different categories of cruciform specimens. In the first category, two specimens, each having two arms have been tested under uniaxial loading. Out of the two specimens, one specimen has been tested at subzero temperature (- 70 deg C) and the other specimen at room temperature. In the second category, two cruciform specimens, each having four arms with equal length, have been tested under biaxial loading with biaxiality ratio of one. Out of the two specimens, one specimen has been tested at subzero temperature (- 70 deg C) and the other specimen at room temperature. In the third category, two cruciform specimens have been tested under bi-axial loading at subzero temperature (- 70 deg C). The ratio of lengths of transverse arms to longitudinal arms has been taken 1.75 so that ratio of bending stress in longitudinal direction to the bending stress in transverse direction (i.e. biaxiality ratio) becomes 2:1 upon loading. It is found that the biaxiality ratio starts deviating from the initial value of 2:1 to 1:1, once the yielding of the arms starts, hence, the dimensions of the cruciform specimens, test temperature and the crack configuration have been selected in such a way that the crack initiates before the biaxiality ratio deviates from 2:1. When the testing of cruciform specimen is carried out at - 70 deg C the biaxiality ratio remains around 2:1 till the crack initiates, hence, both the specimens with biaxiality ratio 2:1 have been tested at subzero temperature. Three dimensional elastic-plastic finite element (FE) analyses have been carried out for all the specimens. Results obtained from the FE analyses have been found to be in good agreement with the test data. Crack initiation loads have also been predicted numerically based on the initiation toughness (Ji)SZW. Effect of multiaxiality on various fracture parameters has also been discussed. (author)

2011-01-01

88

Vertically aligned biaxially textured molybdenum thin films  

International Nuclear Information System (INIS)

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

2011-09-15

89

Cruciform specimen design for testing advanced aeropropulsion materials under cyclic in-plane biaxial loading  

Science.gov (United States)

Investigating material behavior under complex stress states is often done using in-plane biaxial loading approach. Utilizing such techniques requires using cruciform type specimens fabricated from plate material tested by gripping the specimen at four locations and loaded along two orthogonal axes. Servohydraulic systems are generally used in this application which is similar to those used for uniaxial testing. These kind of testing capabilities are currently being conducted at NASA Glenn Research Center via a new in-house testing facility. This is in support of the development of major components for the Stirling Radioisotope Generator (SRG). It is also used to assist in the generation of an analytical life prediction methodology [1] and to experimentally verify the flight-design component's life. Further, this work is intended to carry the immediate goal of developing a specimen design that is fully compatible with the in-plane biaxial testing systems installed at NASA Glenn Research Center [2]. Thus, details of the specimen design and its applicability to the ongoing experimental activities are being reported and discussed. Finite element analyses were carried out to optimize the geometry of specimen and to evaluate the stress response under biaxial loading conditions [3, 4]. The material of interest used in this research is nickel based superalloy. The data presented concluded that the specimen can be used to investigate the deformation behavior under general forms of biaxial loading. The provided measurement and observation are limited to 1-in [2.54 cm] diameter circular region at the specimen center.

Abdul-Aziz, Ali; Krause, David

2006-04-01

90

Biaxial Loading Tests for steel containment vessel  

Energy Technology Data Exchange (ETDEWEB)

The Nuclear Power Engineering Corporation (NUPEC) has conducted a 1/10 scale of the steel containment vessel (SCV) test for the understanding of ultimate structural behavior beyond the design pressure condition. Biaxial Loading Tests were supporting tests for the 1/10 scale SCV model to evaluate the method of estimating failure conditions of thin steel plates under biaxial loading conditions. The tentative material models of SGV480 and SPV490 were obtained. And the behavior of SGV480 and SPV490 thin steel plates under biaxial loading conditions could be well simulated by FE-Analyses with the tentative material models and Mises constitutive law. This paper describes the results and the evaluations of these tests. (author)

Miyagawa, T. [Nuclear Power Engineering Corp., Tokyo (Japan); Wright, D.J.; Arai, S.

1999-07-01

91

Models for biaxial nematic liquid crystals  

Science.gov (United States)

In the Landau-de Gennes theory, the order parameter describing a biaxial nematic liquid crystal is, at each point of the region occupied by the system, a symmetric, traceless 3 × 3 matrix with three distinct eigenvalues. In the constrained case of matrices with constant eigenvalues, the order parameter space identifies with an eightfold quotient of the 3-sphere, and a configuration of a biaxial nematic liquid crystal is described by a map into such a quotient. We express the (simplest form of the) Landau-de Gennes elastic free-energy density of biaxial nematics as a density on maps into the 3-sphere, whose functional dependence is restricted by the requirements that it is well-defined on the class of configuration maps (residual symmetry) and is independent of arbitrary superposed rigid rotations (frame indifference). This is a report on joint work with D. Mucci [18], to which we refer for more details and applications.

Nicolodi, Lorenzo

2013-02-01

92

Models for biaxial nematic liquid crystals  

International Nuclear Information System (INIS)

In the Landau-de Gennes theory, the order parameter describing a biaxial nematic liquid crystal is, at each point of the region occupied by the system, a symmetric, traceless 3 × 3 matrix with three distinct eigenvalues. In the constrained case of matrices with constant eigenvalues, the order parameter space identifies with an eightfold quotient of the 3-sphere, and a configuration of a biaxial nematic liquid crystal is described by a map into such a quotient. We express the (simplest form of the) Landau-de Gennes elastic free-energy density of biaxial nematics as a density on maps into the 3-sphere, whose functional dependence is restricted by the requirements that it is well-defined on the class of configuration maps (residual symmetry) and is independent of arbitrary superposed rigid rotations (frame indifference). This is a report on joint work with D. Mucci [18], to which we refer for more details and applications.

2013-02-08

93

The biaxial flexural strength and fatigue property of Lava Y-TZP dental ceramic.  

UK PubMed Central (United Kingdom)

OBJECTIVES: The development of yttrium oxide partially stabilized zirconia (Y-TZP) has allowed the use of ceramic in load-bearing sites. The aim of this study was to evaluate and compare the biaxial flexural strength, hardness and fatigue life of colored and uncolored zirconia in the LAVAtrade mark system. MATERIALS AND METHODS: Eight groups (n=30) of standardized disc specimens (15mmx1.3mm) were used to examine the biaxial flexural strength (ISO 6872 standard) using a Dartec HC10 Fatigue Tester (Zwick Ltd., UK) and Vickers hardness was also measured. The uncolored, FS4, FS7 groups were also submitted to dynamic fatigue testing to produce stress-number curves. The strength reliability was analyzed using Weibull distribution. RESULTS: All groups had a mean biaxial flexural strength, hardness and Weibull modulus (m) of approximately 1100MPa, 1300HV and 9.8-12.9, respectively. One-way analysis of variance (ANOVA) showed no significant difference in biaxial flexural strength among the eight groups (p>0.05). Two-way ANOVA showed no significant differences in hardness values among groups except FS1 and FS5 which had significantly higher hardness values than FS4 and FS7 (p<0.001) and FS5 also had a higher hardness value than FS3 (p<0.05). Additionally, uncolored, FS4 and FS7 survived at 5x10(5) cycles at a stress level in the range of 60-65% of the mean biaxial flexural strength. CONCLUSION: There was no difference in flexural strength of uncolored and colored Y-TZP ceramic. The fatigue limit of uncolored, FS4 and FS7 zirconia may be defined as lying between 60 and 65% of the stress to failure.

Pittayachawan P; McDonald A; Petrie A; Knowles JC

2007-08-01

94

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

1993-01-01

95

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1993-12-31

96

Self-aligning biaxial load frame  

Energy Technology Data Exchange (ETDEWEB)

An self-aligning biaxial loading apparatus for use in testing the strength of specimens while maintaining a constant specimen centroid during the loading operation. The self-aligning biaxial loading apparatus consists of a load frame and two load assemblies for imparting two independent perpendicular forces upon a test specimen. The constant test specimen centroid is maintained by providing elements for linear motion of the load frame relative to a fixed crosshead, and by alignment and linear motion elements of one load assembly relative to the load frame.

Ward, Michael B. (Idaho Falls, ID); Epstein, Jonathan S. (Idaho Falls, ID); Lloyd, W. Randolph (Idaho Falls, ID)

1994-01-01

97

Microcracking of the alloy 800HT under biaxial fatigue; Mikrorissverhalten der Legierung 800HT unter biaxialer Ermuedung  

Energy Technology Data Exchange (ETDEWEB)

An accurate prediction of the flawed service life under operating loads must be based on data including the effects of multiaxial stresses on the mechanisms of microcracking and microcrack propagation. Such data can be obtained only by experimental testing under multiaxial loads and measurement of the crack growth. The paper explains the microcracking of the alloy 800HT at ambient temperatures under biaxial stresses. (orig./RHM) [Deutsch] Fuer eine genaue Vorhersage der Anrisslebensdauer unter Betriebsbelastung muss der Einfluss der Mehrachsigkeit auf die Mechansimen der Mikrorissbildung und -ausbreitung bekannt sein. Dies ist nur durch experimentelle Untersuchungen des Verhaltens kurzer Risse bei solchen Belastungen moeglich. In diesem Beitrag wird das Kurzrissverhalten der Legierung 800HT bei Umgebungstemperatur unter biaxialen Belastungen beschrieben. (orig./RHM)

Mu, Z. [Max-Planck-Inst. fuer Eisenforschung GmbH, Duesseldorf (Germany); Vehoff, M. [Max-Planck-Inst. fuer Eisenforschung GmbH, Duesseldorf (Germany)

1993-12-31

98

Towards the biaxial nematic phase via specific intermolecular interactions  

CERN Document Server

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

Omnes, L

2001-01-01

99

Biaxially textured metal substrate with palladium layer  

Energy Technology Data Exchange (ETDEWEB)

Described is an article comprising a biaxially textured metal substrate and a layer of palladium deposited on at least one major surface of the metal substrate; wherein the palladium layer has desired in-plane and out-of-plane crystallographic orientations, which allow subsequent layers that are applied on the article to also have the desired orientations.

Robbins, William B [Maplewood, MN

2002-12-31

100

Influence of f. c. c. rolling textures on biaxial sheet stretching  

Energy Technology Data Exchange (ETDEWEB)

The behavior of sheet metals initially having f.c.c. rolling textures is simulated under biaxial stretching conditions. A rate-sensitive crystal plasticity model together with the full-constraint Taylor theory is used. Closed-form analytical solutions for the stress states, slip distributions and lattice spins are obtained for the ideal orientations of f.c.c. rolling textures. The three-dimensional lattice rotation fields at these ideal orientations, and their evolution paths in Euler space, are predicted for various biaxial stretching ratios. Similar simulations are also carried out for polycrystalline textures. It is shown that, for a copper-type initial texture (the [beta]-fiber) and a strain ratio [rho] < 0.5, the corresponding biaxial-stretching texture will not be much different from the initial texture. However, for [rho] > 0.5 the [beta]-fiber deteriorates and the [alpha]-fiber increases relatively quickly. If the initial texture is the R-recrystallization texture (cube + S[sub 1]), the main component of the simulated biaxial-stretching textures is the fiber near [beta] for [rho] < 0.5, but the [alpha]-fiber for [rho] > 0.5. The simulated equibiaxial-stretching texture is in agreement with the published measured textures for aluminum sheets.

Zhou, Y.; Neale, K.W. (Univ. de Sherbrooke, Quebec (Canada). Faculte des Sciences Appliquees)

1994-06-01

 
 
 
 
101

Development of an apparatus for biaxial testing using cruciform specimens  

Science.gov (United States)

A testing apparatus has been developed to study the behavior of sheet metals and composite materials under monotonic and cyclic biaxial loading conditions. This test facility employs cruciform specimens that are loaded in their plane. Problems encountered while developing the test system are discussed. The difficulties common to test methods employing cruciform specimens relate to the design of a suitable specimen geometry and to the determination of the stresses throughout the specimen. A method for designing an optimal geometry for these specimens is based on the statistical tools of factorial and response surface designs. The statistical method, coupled with a finite-element analysis of the specimen, was successfully applied to optimize the geometry of a cruciform specimen with a circular reduced central region.

Makinde, A.; Thibodeau, L.; Neale, K. W.

1992-06-01

102

Method for making biaxially textured articles by plastic deformation  

Energy Technology Data Exchange (ETDEWEB)

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

Goyal, Amit (Knoxville, TN)

2002-01-01

103

Biaxial crystal-based optical tweezers  

DEFF Research Database (Denmark)

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.

Angelsky, Oleg V.; Maksimyak, Andrew P.

2010-01-01

104

Damage and failure behavior of metal matrix composites under biaxial loads  

Science.gov (United States)

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.

Kirkpatrick, Steven Wayne

105

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

2007-01-01

106

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

International Nuclear Information System (INIS)

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

1993-01-01

107

Magnetic response of FeNbCuBSi RQ ribbons to bi-axial strain  

International Nuclear Information System (INIS)

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

2000-06-02

108

Endothelial cell loss: Biaxial small-incision torsional phacoemulsification versus biaxial small-incision longitudinal phacoemulsification.  

UK PubMed Central (United Kingdom)

PURPOSE: To compare clinical results of biaxial small-incision torsional phacoemulsification and biaxial small-incision longitudinal phacoemulsification. SETTING: Department of Ophthalmology, School of Medicine, Namik Kemal University, Tekirdag, Turkey. DESIGN: Randomized controlled clinical trial. METHODS: Eyes with high-density nuclear cataract were assigned to have biaxial longitudinal (microburst mode) or biaxial torsional phacoemulsification. The main outcomes included corrected distance visual acuity (CDVA), central corneal thickness (CCT), central endothelial cell density (ECD), total ultrasound time (UST), cumulative dissipated energy (CDE), percentage total equivalent power in position 3, and balanced salt solution volume. Postoperative follow-up was at 1 day, 1 week, and 1 and 3 months. RESULTS: Each group comprised 35 patients (35 eyes). Three months postoperatively, the mean CDVA for each group was 0.02 logMAR and the mean CCT returned to the preoperative level (P=.589 and P=.554, respectively). During the postoperative follow-up, the percentage of mean endothelial cell loss in both groups was between 35.4% and 39.1%; there was no statistically significant difference between the groups (P>.05). The mean CDE, UST, percentage total equivalent power in position 3, and balanced salt solution volume values were similar in the 2 groups (P>.05). CONCLUSION: The risk for high endothelial cell loss should be considered when the phacoemulsification of high-density nuclear cataracts is performed using either method. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Gonen T; Sever O; Horozoglu F; Yasar M; Keskinbora KH

2012-11-01

109

Structures having enhanced biaxial texture and method of fabricating same  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1998-01-01

110

Structures having enhanced biaxial texture and method of fabricating same  

Energy Technology Data Exchange (ETDEWEB)

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.

Goyal, Amit (300 Walker Springs Rd., Knoxville, TN 37923); Budai, John D. (104 Conners Pl., Oak Ridge, TN 37830); Kroeger, Donald M. (716 Villa Crest Dr., Knoxville, TN 37923); Norton, David P. (1013 Turnberry Dr., Knoxville, TN 37923); Specht, Eliot D. (10639 Rivermist La., Knoxville, TN 37922); Christen, David K. (103 Artesia Dr., Oak Ridge, TN 37830)

1999-01-01

111

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.

1976-11-29

112

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)

2012-01-01

113

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

1994-01-01

114

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

Energy Technology Data Exchange (ETDEWEB)

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.

Bass, B.R.; Bryson, J.W.; Theiss, T.J.; Rao, M.C. [Oak Ridge National Lab., TN (United States)

1994-01-01

115

Pressure and Stress Effects on Diffusion in Si  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 hydr...

Aziz, Michael

116

Conductive and robust nitride buffer layers on biaxially textured substrates  

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-03-31

117

Biaxially stretched nematic liquid crystalline elastomers.  

UK PubMed Central (United Kingdom)

The biaxial stretching of sheets of liquid crystalline neo-Hookean elastomer has been studied in the isotropic case. The results suggest two types of laminate structures in the process of quasiconvexification of the free energy, a fact that implies the appearance of several shear terms in the deformation gradient matrix. More that one decomposition of the deformation gradient is possible, which is consistent with a bifurcation in the undeformed configuration (? = 1) . This situation is similar to the well-known Rivlin's problem of the triaxial symmetric traction of a neo-Hookean cube. The problem can easily be generalized for an anisotropic material by introducing a semisoft term in the free-energy expression. In this case, the horizontal plateau corresponding to the minimal energy, characteristic of the soft elasticity, disappears, and only an equilibrium condition is obtained.

Diaz-Calleja R; Riande E

2012-01-01

118

Fatigue and creep-fatigue strength of 304 steel under biaxial strain conditions  

International Nuclear Information System (INIS)

A series of fatigue and creep-fatigue tests were conducted with 304 stainless steel at 550degC under a variety of biaxial strain conditions. Fatigue life under nonproportional loading conditions showed a significant life reduction compared with that of proportional loading, and this life reduction was reasonably estimated by taking into account the strain paths along which the strain history is imposed. Furthermore, a marked life reduction was shown to occur under nonproportional loading by imposing a strain hold period at a peak tensile strain. This life reduction was evaluated by the linear damage rule. It was shown to be possible to estimate the fatigue damage and the creep damage under nonproportional loading by a linear damage rule by estimating a stress relaxation behavior by Mises-type equivalent stress or Huddleston-type equivalent stress. (author).

1990-01-01

119

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

Science.gov (United States)

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

Enatsu, Ryotaro; Kuwabara, Toshihiko

2011-08-01

120

A new direct biaxial testing machine for anisotropic materials  

Science.gov (United States)

A screw-driven new biaxial testing machine for the realization of experimental investigations on anisotropic sheet materials, such as composite plates or rolled sheet metals, is presented. The described mechanical concept and servocontrol system allow cruciform specimens to be subjected to large strain biaxial tensile and compressive tests without kinematic incompatibilities. Moreover, for the proper implementation of biaxial tensile tests, the specific problems linked to the anisotropic properties of the investigated materials are taken into account; therefore, for the first time, the biaxial machine is supplied with the original 'off-axes testing device,' consisting of hinged fixtures with knife-edges at each arm of the cruciform specimen. A recently developed optimization method for the optimal design of flat tensile cruciform specimens is shortly reviewed. Numerical simulations illustrate the decisive superiority of the optimized specimen compared with specimen designs proposed in the literature, as well as the necessity to use the 'off-axes' testing technique in biaxial tests on anisotropic materials.

Boehler, J. P.; Demmerle, S.; Koss, S.

1994-03-01

 
 
 
 
121

Orientation dependence of twinning in biaxial stretching of commercially pure titanium. Kogyoyo jun titan no nijiku hippari henkei ni okeru sosho henkei no kessho hoi izonsei  

Energy Technology Data Exchange (ETDEWEB)

To investigate the crystal orientation dependence of twinning in biaxial stretching of commercially pure titanium plate, the relationship between the twinning operating in biaxial stretching deformation and the crystal orientation is obtained to discuss the problem from the viewpoints of the relation between the crystal orientation and resolved shear stress as well as of the magnitude of the resolved shear strength. Based on the result, planar anistropy of twin density observed in anistropic biaxial stretch deformation is investigated. Twinning deformation operates only in the crystal orientation where the resolved shear stress works in the twinning orientation. The activity of twinning deformation depends mainly on the magnitude of Schmid factors. In the crystal orientation where inequivalent twinning has Schmid factors of similar degree, twinning which operates can not be determined by the magnitude of Schmid factors only. The planar anistropy deformation twin density observed in anistropic biaxial stretching can be explained by considering the twinning deformation against the main orientation of the texture and the magnitude of Schmid factors of anistropic slip. 13 refs., 9 figs., 1 tab.

Ishiyama, S. (Nippon Stainless Steel Co. Ltd., Tokyo (Japan)); Hanada, S. (Tohoku Univ., Sendai (Japan). Inst. for Materials Research)

1991-12-20

122

Depletion-induced biaxial nematic states of boardlike particles.  

UK PubMed Central (United Kingdom)

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.

Belli S; Dijkstra M; van Roij R

2012-07-01

123

Method of forming biaxially textured alloy substrates and devices thereon  

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-01-01

124

Method of forming biaxially textured alloy substrates and devices thereon  

Energy Technology Data Exchange (ETDEWEB)

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

Goyal, Amit (Knoxville, TN); Specht, Eliot D. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Paranthaman, Mariappan (Knoxville, TN)

1999-01-01

125

Thermally insensitive, single-crystal, biaxial electro-optic modulators  

Energy Technology Data Exchange (ETDEWEB)

All optically biaxial crystals exhibit orientations in which they behave as thermally insensitive (TI) wave plates. Given sufficient electro-optic coupling at these orientations, biaxial, ferroelectric crystals may be advantageously employed as single-crystal, temperature-insensitive electro-optic modulators. I have experimentally confirmed the TI orientation in the principal dielectric plane of the biaxial crystal KTiOPO{sub 4} (KTP). KTP behaves as a TI wave plate at 33.7 deg from the {ital Z} axis in the {ital X}--{ital Z} principal plane. The effective electro-optic coupling, {ital R}{sub eff}, at this orientation is 19 pm/V. The electro-optic coupling and utility of these TI orientations in KTiOAsO{sub 4} and KNbO{sub 3} are also examined. The calculated {ital R}{sub eff} of KNbO{sub 3} at the TI orientation is expected to be {gt}2000 pm/V.

Ebbers, C.A. [Lawrence Livermore National Laboratory, 7000 East Avenue, L-250, Livermore, California 94550 (United States)

1995-06-01

126

Residual stress induced atomic scale buckling of diamond carbon coatings on silicon substrate  

Energy Technology Data Exchange (ETDEWEB)

This paper investigates the atomic scale buckling of diamond carbon coatings on silicon substrate caused by residual stresses in two orthogonal directions. It was found that different buckling patterns occurred when the ratio of the residual stresses in the two directions were changed. The size of wrinkles increased on going from uniaxial to biaxial compression of the residual stress fields. A telephone-cord like buckling mode took place when the residual stresses were bi-axially equal.

Mylvaganam, K.; Zhang, L.C

2003-02-03

127

Residual stress induced atomic scale buckling of diamond carbon coatings on silicon substrate  

International Nuclear Information System (INIS)

This paper investigates the atomic scale buckling of diamond carbon coatings on silicon substrate caused by residual stresses in two orthogonal directions. It was found that different buckling patterns occurred when the ratio of the residual stresses in the two directions were changed. The size of wrinkles increased on going from uniaxial to biaxial compression of the residual stress fields. A telephone-cord like buckling mode took place when the residual stresses were bi-axially equal

2003-02-03

128

Topology Optimization of Stressed Capacitive RF MEMS Switches  

DEFF Research Database (Denmark)

Geometry design can improve a capacitive radio-frequency microelectromechanical system switch's reliability by reducing the impacts of intrinsic biaxial stresses and stress gradients on the switch's membrane. Intrinsic biaxial stresses cause stress stiffening, whereas stress gradients cause out-of-plane curling. We use topology optimization to systematically generate designs, by minimizing stress stiffening, minimizing curling, or minimizing stress stiffening while constraining the curling behavior. We present the corresponding problem formulations and sensitivity derivations and discuss the role of key elements in the problem formulation.

Philippine, Mandy A.; Sigmund, Ole

2013-01-01

129

Method for forming biaxially textured articles by powder metallurgy  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2002-01-01

130

Formation of biaxial-stretching textures in FCC sheet metals  

Energy Technology Data Exchange (ETDEWEB)

Biaxial stretching is an important deformation mode for fabricating final products from sheet metals. Mechanical anisotropy, resulting mainly from crystallographic textures, greatly affects forming processes as well as the shapes and properties of products. In this paper, the formation of textures during the biaxial stretching of FCC sheet metals is investigated using a rate-sensitive crystal plasticity model [1-3] together with the full constraint Taylor theory. The strain-rate sensitivity m is specified to m = 0.005 in this investigation to represent cold working. (orig.)

Zhou, Y. (Faculte des Sciences Appliquees, Univ. de Sherbrooke, PQ (Canada)); Neale, K.W. (Faculte des Sciences Appliquees, Univ. de Sherbrooke, PQ (Canada))

1994-01-01

131

Kinetics of thermal damage to a collagenous membrane under biaxial isotonic loading.  

UK PubMed Central (United Kingdom)

Prior isothermal uniaxial isotonic tests on tendons reveal that higher temperatures hasten the rate of thermal denaturation whereas larger mechanical loads delay it; moreover, these findings suggest a time-temperature-load equivalency whereby similar levels of denaturation, as reflected by tissue shrinkage, can be attained via many combinations of heating time, temperature level, and mechanical loading. Yet, most tissues and organs experience multiaxial loads in vivo, and their microstructure differs significantly from that of tendons, thus, we must also evaluate the effects of multiaxial stresses on the kinetics of denaturation in other tissues. In this paper, we describe a new experimental approach for performing isothermal biaxial isotonic tests on thin sheet-like specimens and we report effects of various thermomechanical loads on the rate and amount of multiaxial shrinkage of bovine epicardium. Consistent with uniaxial studies, epicardial shrinkage generally increased sigmoidally with heating time, and a characteristic heating time revealed increases in the rate of shrinkage with higher temperature and decreases with larger biaxial loads. Although this characteristic time exhibited an Arrhenius-type character, time-temperature-load equivalency was not obtained when scaling time with this metric. General multiaxial thermomechanics is thus too complex to explain via a simple extension of uniaxial findings on tendons and there is a pressing need for more data and an appropriate theoretical framework.

Harris JL; Humphrey JD

2004-02-01

132

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

Science.gov (United States)

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

Abdul-Aziz, Ali; Krause, David

2006-04-01

133

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

Science.gov (United States)

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

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

2011-01-01

134

Biaxial testing of canine annulus fibrosus tissue under changing salt concentrations  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese A mecânica in vivo do anel fibroso do disco intervertebral é baseada em carregamento biaxial ao invés de uniaxial. As propriedades materiais do anel estão intimamente ligadas à osmolaridade no tecido. O artigo apresenta experimentos de relaxação biaxiais do anel fibroso de um tecido canino sob mudanças abruptas na concentração externa de sal. A assinatura da força devido à mudança brusca de salinidade resulta em uma progressiva e monótona mudança na tensão (more) 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 traci (more) ng 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.

Huyghe, Jacques M.

2010-03-01

135

Biaxial testing of canine annulus fibrosus tissue under changing salt concentrations  

Directory of Open Access Journals (Sweden)

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

Jacques M. Huyghe

2010-01-01

136

Comeback of biaxial solar tracking systems; Comeback der Zweiachser  

Energy Technology Data Exchange (ETDEWEB)

Although experts do not see much of a future for solar tracking systems, it is an astonishingly vital market segment. It may be a niche market, but of global importance. This market survey of solar tracking sytems presents new competitors and products. It is shown that biaxial tracking systems are gaining new impetus as well.

Thompson, Valerie

2012-07-01

137

Biaxial Compressive Strain Engineering in Graphene/Boron Nitride Heterostructures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Strain engineered graphene has been predicted to show many interesting physics and device applications. Here we study biaxial compressive strain in graphene/hexagonal boron nitride heterostructures after thermal cycling to high temperatures likely due to their thermal expansion coefficient mismatch....

Pan, Wei; Xiao, Jianliang; Zhu, Junwei; Yu, Chenxi; Zhang, Gang; Ni, Zhenhua; Watanabe, K.; Taniguchi, T.; Shi, Yi; Wang, Xinran

138

High Tc YBCO superconductor deposited on biaxially textured Ni substrate  

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-01-01

139

Effect of strain on deformation in biaxial expension of zirconium  

International Nuclear Information System (INIS)

[en] Shaping is more difficult for zirconium than for titanium. The difference in behavior comes from twinning occuring in titanium which is not the case for zirconium twin crystals were created in zirconium by strain of 4% at low temperature (-1960C), the ultimate deformation temperature being 1750C. Biaxial strain gives the best results

1985-01-01

140

Biaxial tests of some overcored samples from AECL's underground research laboratory, Lac du Bonnet, Manitoba. Report No. MRL 89-55(TR)  

Energy Technology Data Exchange (ETDEWEB)

Atomic Energy of Canada Ltd. has constructed an underground research laboratory (URL) in the Lac du Bonnet batholith, located 100 km northeast of Winnipeg, Manitoba. The URL will be used to investigate some of the issues associated with the safe design, construction and operation of a vault for the disposal of high-level nuclear waste deep in plutonic rock. One of the issues is whether the in situ stress condition in a plutonic rock body and the stresses induced around an excavation in such a body can be understood. This report gives the results of biaxial tests and biaxial tests with axial load to examine the effect of axial and side loads on the strains measured on the inside and on the outside of overcored rock samples obtained in the URL and the elastic constants derived from them. The rock is a massive, grey, medium to coarse grained prophyritic granite.

Lau, J.S.O.

1989-01-01

 
 
 
 
141

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

CERN Multimedia

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...

Fadeyeva, Tatyana; Anischenko, Pavel; Volyar, Alexander

2011-01-01

142

Theory of nine elastic constants of biaxial nematics  

Science.gov (United States)

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

Liu, Hong

2008-03-01

143

Isotropic to biaxial nematic phase transition in an external magnetic field  

Science.gov (United States)

The first theoretical observation of the tricritical point for the isotropic to biaxial nematic phase transition of biaxial nematic liquid crystals in the presence of an external field is reported. The influence of an external magnetic field on the isotropic to biaxial nematic phase transition have been studied using Landau phenomenological theory. Topological classification of phase diagrams in the field – temperature coordinates is performed. It is shown that for a particular value of the magnetic field, the first order isotropic to biaxial nematic phase transition becomes second order phase transition at a tricritical point.

Mukherjee, Prabir K.; Rahman, Muklesur

2013-09-01

144

Stress  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The concept of stress is often mistaken. Its correct usage stems from the meaning in physical medicine, and many facets of stress are missed because this is not generally realized. This paper defines a psychiatric model of stress and describes a method by which stress can be quantified in various in...

Pearce, K. I.

145

Comparisons of planar and tubular biaxial tensile testing protocols of the same porcine coronary arteries.  

UK PubMed Central (United Kingdom)

To identify the orthotropic biomechanical behavior of arteries, researchers typically perform stretch-pressure-inflation tests on tube-form arteries or planar biaxial testing of splayed sections. We examined variations in finite element simulations (FESs) driven from planar or tubular testing of the same coronary arteries to determine what differences exist when picking one testing technique vs. another. Arteries were tested in tube-form first, then tested in planar-form, and fit to a Fung-type strain energy density function. Afterwards, arteries were modeled via finite element analysis looking at stress and displacement behavior in different scenarios (e.g., tube FESs with tube- or planar-driven constitutive models). When performing FESs of tube inflation from a planar-driven constitutive model, pressure-diameter results had an error of 12.3% compared to pressure-inflation data. Circumferential stresses were different between tube- and planar-driven pressure-inflation models by 50.4% with the planar-driven model having higher stresses. This reduced to 3.9% when rolling the sample to a tube first with planar-driven properties, then inflating with tubular-driven properties. Microstructure showed primarily axial orientation in the tubular and opening-angle configurations. There was a shift towards the circumferential direction upon flattening of 8.0°. There was also noticeable collagen uncrimping in the flattened tissue.

Keyes JT; Lockwood DR; Utzinger U; Montilla LG; Witte RS; Vande Geest JP

2013-07-01

146

Determination of principal stresses by Barkhausen effect  

International Nuclear Information System (INIS)

[en] Root-mean-square stresses of Barkhausen noise (BN) and amplitudes of the first three harmonics of the BN stress envelope have been studied in the course of tests of plane crosslike steel St.3 and steel 20 specimens for biaxial tension. Techniques are suggested for determining principal stresses by the magnetic noise method with the help of constant BN parameters on the principal stress plane

1990-01-01

147

Optical confirmation of biaxial nematic (Nb) phase in a bent-core mesogen  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A bent-core mesogen with different end groups has been studied for different surface conditions in both planar and homeotropic cells using techniques for measuring biaxiality and optical switching. Biaxial nematic phase observed in between the uniaxial nematic and smectic phases is evidenced by a sh...

PANOV, VITALY; VIJ, JAGDISH KUMAR

148

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-01-01

149

Initial results of the influence of biaxial loading on fracture toughness  

International Nuclear Information System (INIS)

A testing program to examine the influence of biaxial loads on the fracture toughness of shallow-flaw specimens under conditions prototypic of a reactor pressure vessel was begun. Existing data suggest that shallow-flaw specimens under biaxial loading will exhibit a toughness reduction compared to comparable uniaxial specimens. Quantification of this toughness reduction is the main goal of the biaxial fracture toughness program. A cruciform specimen with a two-dimensional shallow through-thickness flaw under a biaxial load ratio of 0.6:1 was used for biaxial fracture toughness testing. The critical fracture load for each specimen was approximately the same, but the uniaxial specimen withstood substantially more deformation at failure than did the biaxial specimens. Three-dimensional, elastic-plastic, finite-element posttest analyses were necessary to estimate fracture toughness. In all cases, agreement between the measured and computed load vs deformation responses was excellent. Toughness values for the cruciform specimens were compared with data from previously tested, deep- and shallow-crack specimens. Results from these tests indicate that the shallow-crack toughness increase is partially, but not totally, removed by the application of biaxial loading. However, additional data are required to solidify these conclusions. A proposed test matrix for additional uniaxial and biaxial testing is described. This report has been designated HSST Report No. 138

1993-01-01

150

Initial results of the influence of biaxial loading on fracture toughness  

Energy Technology Data Exchange (ETDEWEB)

A testing program to examine the influence of biaxial loads on the fracture toughness of shallow-flaw specimens under conditions prototypic of a reactor pressure vessel was begun. Existing data suggest that shallow-flaw specimens under biaxial loading will exhibit a toughness reduction compared to comparable uniaxial specimens. Quantification of this toughness reduction is the main goal of the biaxial fracture toughness program. A cruciform specimen with a two-dimensional shallow through-thickness flaw under a biaxial load ratio of 0.6:1 was used for biaxial fracture toughness testing. The critical fracture load for each specimen was approximately the same, but the uniaxial specimen withstood substantially more deformation at failure than did the biaxial specimens. Three-dimensional, elastic-plastic, finite-element posttest analyses were necessary to estimate fracture toughness. In all cases, agreement between the measured and computed load vs deformation responses was excellent. Toughness values for the cruciform specimens were compared with data from previously tested, deep- and shallow-crack specimens. Results from these tests indicate that the shallow-crack toughness increase is partially, but not totally, removed by the application of biaxial loading. However, additional data are required to solidify these conclusions. A proposed test matrix for additional uniaxial and biaxial testing is described. This report has been designated HSST Report No. 138.

Theiss, T.J.; Bass, B.R.; Bryson, J.W.; McAfee, W.J.; Nanstad, R.K.; Pennell, W.E.; Rao, M.C. (Oak Ridge National Lab., TN (United States))

1993-06-01

151

Modelization of ratcheting in biaxial experiments  

International Nuclear Information System (INIS)

[en] 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[fr] Une nouvelle equation constitutive viscoplastique a ete developpee afin de permettre la prediction des experiences de deformation progressive sur les structures mecaniques des reacteurs a neutrons rapides. Ce modele est base essentiellement sur une extension de l'equation d'Armstrong Frederick pour la variable cinematique; le coefficient du terme de restauration dynamique dans cette equation est une fonction simultanee de la deformation inelastique instantanee et de la deformation inelastique accumulee, definie de facon a reproduire le taux de deformation progressive experimentale. La validite du modele est verifiee par comparaison entre les predictions du calcul et les resultats des experiences pratiquees a 6000C sur des eprouvettes tubulaires en acier inoxydable austenitique (17-12 SPH) soumises a un chargement cyclique de torsion et a une charge axiale constante

1989-01-01

152

Measuring stresses in rock  

Energy Technology Data Exchange (ETDEWEB)

Measurements by the overcoring method using inductive measuring transducers have given very good results. The effect of faults (e.g. fissures) can be recognised from measurements during the overcoring process. This is a decided advantage of this method of measurement compared to measurements with biaxial (door stopper) or triaxial load cells, which, however, require only short overcoring distances. The combination of different processes of measurement has proved successful for carrying out extensive stress investigations.

Mueller, D.

1981-09-01

153

IVUS-Based Computational Modeling and Planar Biaxial Artery Material Properties for Human Coronary Plaque Vulnerability Assessment  

Science.gov (United States)

Image-based computational modeling has been introduced for vulnerable atherosclerotic plaques to identify critical mechanical conditions which may be used for better plaque assessment and rupture predictions. In vivo patient-specific coronary plaque models are lagging due to limitations on non-invasive image resolution, flow data, and vessel material properties. A framework is proposed to combine intravascular ultrasound (IVUS) imaging, biaxial mechanical testing and computational modeling with fluid-structure interactions and anisotropic material properties to acquire better and more complete plaque data and make more accurate plaque vulnerability assessment and predictions. Impact of pre-shrink-stretch process, vessel curvature and high blood pressure on stress, strain, flow velocity and flow maximum principal shear stress was investigated.

Liu, Haofei; Cai, Mingchao; Yang, Chun; Zheng, Jie; Bach, Richard; Kural, Mehmet H.; Billiar, Kristen L.; Muccigrosso, David; Lu, Dongsi; Tang, Dalin

2012-01-01

154

High magnification crack-tip field characterisation under biaxial conditions  

Directory of Open Access Journals (Sweden)

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

B. Moreno; P. Lopez-Crespo; J. Zapatero

2013-01-01

155

Plastic instabilities during biaxial testing of Al-Fe-Si foils  

Energy Technology Data Exchange (ETDEWEB)

Al-Fe-Si foils with an appropriate treatment exhibit, during bulge testing, different types of plastic instabilities. In the as-received foils only uniform straining is observed. Solution treatment at 590 C for 30 min results in the appearance of a negative strain rate sensitivity and various types of instabilities. After instantaneous changes of the stress rate during bulging, significant instabilities on stress - strain curves appear as a result of pronounced strain rate oscillations. The amplitude of these oscillations decay with increasing time, and after a transient period, straining becomes uniform again. Spontaneous discontinuous yielding occurs in specimens annealed at 630 C for 30 min. The main features of these instabilities are the presence of critical strains for the onset of oscillations, their existence in a limited range of strains and the presence of a negative strain rate sensitivity. These results are consistent with recent theoretical models derived for uniaxial straining. The differences in sample behavior in biaxial and uniaxial testing are discussed. (orig.)

Cieslar, M.; Karimi, A.; Martin, J.L. [Swiss Federal Inst. of Technol. (EPFL), Lausanne (Switzerland). IPMC, FSB

2002-07-01

156

STRESS  

Directory of Open Access Journals (Sweden)

Full Text Available Objectives: To assess different level of stress and reaction to those stressors among undergraduate medical students and also observe an association between different academic years, if any exists. Design of the study: Cross-sectional study. Settings: Islamic International medical college- a private medical college in Rawalpindi. Period: From 2006 to 2007. Material & methods: Questionnaire used was a stress inventory called students life stress inventory. It was distributed to all registered MBBS students at IIMC in years 1- 5 who voluntarily participated. 403 out of 500 students completed the questionnaire with response rate 81.6%. Results: Data was analyzed through SPSS by applying different statistical tests, which were ANOVA, and t test. Results reveal that 21.53% students were mildly stressed, 39.12% students were moderately stressed and 12.64% students were severely stressed. Significant gender differences were found on almost all the sub-scales. The findings reveal that females face more stressors especially conflicts, emotional and behavioral (p < .01), stress was more significant between boarders as compare to non-boarders. One Way Analyses of variance (ANOVA) was computed to check the significance of differences on mean scores. An analysis of variance on Student Life Stress Inventory is significant, F = (3.774), p <.01. Mean difference indicates that prevalence of stress is higher in first year and final year MBBS students. Conclusion: This study presents pragmatic evidence regarding the psychological health of students in our college. These findings suggest that high levels of stress exist in our students especially significant during first and final years of their course. It is important for us to know the prevalence and causes of student stress, which not only affects their health, but also their academic achievement. Information from this study can be used to develop appropriate intervention programs for medical students, in order to decrease their stress levels.

FARAH RASHID SIDDIQUI

2009-01-01

157

Method of depositing buffer layers on biaxially textured metal substrates  

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-08-27

158

Contractions, a risk for premature rupture of fetal membranes: a new protocol with cyclic biaxial tension.  

UK PubMed Central (United Kingdom)

This study aims at investigating the effect of repeated mechanical loading on the rupture and deformation properties of fetal membranes. Ten membranes delivered by cesarean sections were tested using a custom-built inflation device which provides a multi-axial stress state. For each membrane, a group of samples was first cyclically stretched by application of pressure ranging between 10 and 40 mmHg. After cycles, samples were subjected to inflation up to rupture. Differences between mechanical parameters from cycled and uncycled samples were analyzed. Ten cycles at 40% of mean critical membrane tension--representative of mean physiologic contractions--did not affect strength and stiffness of fetal membranes but reduced the work to rupture, thus indicating that contractions might increase the risk of premature rupture of the membrane. Cyclic testing demonstrated a large hysteresis loop and irreversible deformation on the first cycle, followed by rapid stabilization on subsequent cycles. In 80% of tests, amnion ruptured first and at the periphery of the sample, under uniaxial strain state. Chorion ruptured at higher deformation levels in the middle, under biaxial strain state.

Perrini M; Bürzle W; Haller C; Ochsenbein-Kölble N; Deprest J; Zimmermann R; Mazza E; Ehrbar M

2013-06-01

159

Multiscale strain analysis of tissue equivalents using a custom-designed biaxial testing device.  

UK PubMed Central (United Kingdom)

Mechanical signals transferred between a cell and its extracellular matrix play an important role in regulating fundamental cell behavior. To further define the complex mechanical interactions between cells and matrix from a multiscale perspective, a biaxial testing device was designed and built. Finite element analysis was used to optimize the cruciform specimen geometry so that stresses within the central region were concentrated and homogenous while minimizing shear and grip effects. This system was used to apply an equibiaxial loading and unloading regimen to fibroblast-seeded tissue equivalents. Digital image correlation and spot tracking were used to calculate three-dimensional strains and associated strain transfer ratios at macro (construct), meso, matrix (collagen fibril), cell (mitochondria), and nuclear levels. At meso and matrix levels, strains in the 1- and 2-direction were statistically similar throughout the loading-unloading cycle. Interestingly, a significant amplification of cellular and nuclear strains was observed in the direction perpendicular to the cell axis. Findings indicate that strain transfer is dependent upon local anisotropies generated by the cell-matrix force balance. Such multiscale approaches to tissue mechanics will assist in advancement of modern biomechanical theories as well as development and optimization of preconditioning regimens for functional engineered tissue constructs.

Bell BJ; Nauman E; Voytik-Harbin SL

2012-03-01

160

Characterizing chaotic dynamics from simulations of large strain behavior of a granular material under biaxial compression.  

UK PubMed Central (United Kingdom)

For a given observed time series, it is still a rather difficult problem to provide a useful and compelling description of the underlying dynamics. The approach we take here, and the general philosophy adopted elsewhere, is to reconstruct the (assumed) attractor from the observed time series. From this attractor, we then use a black-box modelling algorithm to estimate the underlying evolution operator. We assume that what cannot be modeled by this algorithm is best treated as a combination of dynamic and observational noise. As a final step, we apply an ensemble of techniques to quantify the dynamics described in each model and show that certain types of dynamics provide a better match to the original data. Using this approach, we not only build a model but also verify the performance of that model. The methodology is applied to simulations of a granular assembly under compression. In particular, we choose a single time series recording of bulk measurements of the stress ratio in a biaxial compression test of a densely packed granular assembly-observed during the large strain or so-called critical state regime in the presence of a fully developed shear band. We show that the observed behavior may best be modeled by structures capable of exhibiting (hyper-) chaotic dynamics.

Small M; Walker DM; Tordesillas A; Tse CK

2013-03-01

 
 
 
 
161

Biaxial fatigue of A533B pressure vessel steel  

Energy Technology Data Exchange (ETDEWEB)

The low-to-intermediate cycle fatigue behavior of A533B steel is investigated using solid round bar specimens tested in combined bending and torsion. Loadings are applied in-phase and 90 deg out-of-phase to produce cases of proportional and nonproportional biaxial fatigue. Out-of-phase loadings are found to be more damaging than in-phase loadings. Two equivalent strain criteria similar to those in the ASME Boiler and Pressure Vessel Code and a newer approach based on cyclic plastic work are used to correlate fatigue lives. The equivalent strain criteria are found to underestimate the fatigue damage in out-of-phase tests, but to provide reasonably good correlations overall. The plastic work approach provides a conservative treatment of the out-of-phase data and somewhat better overall correlation. Cracking behavior observed during the tests is also summarized.

Nelson, D.V.; Rostami, A. [Stanford Univ., CA (United States). Mechanical Engineering Dept.

1997-08-01

162

A resonant biaxial Helmholtz coil employing a fractal capacitor bank.  

Science.gov (United States)

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. PMID:24089847

Martin, James E

2013-09-01

163

A resonant biaxial Helmholtz coil employing a fractal capacitor bank  

Science.gov (United States)

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.

Martin, James E.

2013-09-01

164

A resonant biaxial Helmholtz coil employing a fractal capacitor bank.  

UK PubMed Central (United Kingdom)

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.

Martin JE

2013-09-01

165

Biaxial compressive strain engineering in graphene/boron nitride heterostructures.  

Science.gov (United States)

Strain engineered graphene has been predicted to show many interesting physics and device applications. Here we study biaxial compressive strain in graphene/hexagonal boron nitride heterostructures after thermal cycling to high temperatures likely due to their thermal expansion coefficient mismatch. The appearance of sub-micron self-supporting bubbles indicates that the strain is spatially inhomogeneous. Finite element modeling suggests that the strain is concentrated on the edges with regular nano-scale wrinkles, which could be a playground for strain engineering in graphene. Raman spectroscopy and mapping is employed to quantitatively probe the magnitude and distribution of strain. From the temperature-dependent shifts of Raman G and 2D peaks, we estimate the TEC of graphene from room temperature to above 1000K for the first time. PMID:23189242

Pan, Wei; Xiao, Jianliang; Zhu, Junwei; Yu, Chenxi; Zhang, Gang; Ni, Zhenhua; Watanabe, K; Taniguchi, T; Shi, Yi; Wang, Xinran

2012-11-27

166

Biaxial compressive strain engineering in graphene/boron nitride heterostructures.  

UK PubMed Central (United Kingdom)

Strain engineered graphene has been predicted to show many interesting physics and device applications. Here we study biaxial compressive strain in graphene/hexagonal boron nitride heterostructures after thermal cycling to high temperatures likely due to their thermal expansion coefficient mismatch. The appearance of sub-micron self-supporting bubbles indicates that the strain is spatially inhomogeneous. Finite element modeling suggests that the strain is concentrated on the edges with regular nano-scale wrinkles, which could be a playground for strain engineering in graphene. Raman spectroscopy and mapping is employed to quantitatively probe the magnitude and distribution of strain. From the temperature-dependent shifts of Raman G and 2D peaks, we estimate the TEC of graphene from room temperature to above 1000K for the first time.

Pan W; Xiao J; Zhu J; Yu C; Zhang G; Ni Z; Watanabe K; Taniguchi T; Shi Y; Wang X

2012-01-01

167

Conductive layer for biaxially oriented semiconductor film growth  

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-10-30

168

Biaxial flexural strength of CAD/CAM ceramics.  

UK PubMed Central (United Kingdom)

AIM: Aim of the study was to evaluate the biaxial flexural strength of ceramics processed using the Cerec inLab system. The hypothesis was that the flexural strength would be influenced by the type of ceramic. METHODS: Ten samples (ISO 6872) of each ceramic (N.=50/n.=10) were made using Cerec inLab (software Cerec 3D) (Ø:15 mm, thickness: 1.2 mm). Three silica-based ceramics (Vita Mark II [VM], ProCad [PC] and e-max CAD ECAD]) and two yttria-stabilized tetragonal-zirconia-polycrystalline ceramics (Y-TZP) (e-max ZirCad [ZrCAD] and Vita In-Ceram 2000 YZ Cubes [VYZ]) were tested. The samples were finished with wet silicone carbide papers up to 1?200-grit and polished in a polishing machine with diamond paste (3 µm). The samples were then submitted to biaxial flexural strength testing in a universal testing machine (EMIC), 1 mm/min. The data (MPa) were analyzed using the Kruskal-Wallis and Dunn (5%) tests. Scanning electronic microscopy (SEM) was performed on a representative sample from each group. RESULTS: The values (median, mean±sd) obtained for the experimental groups were: VM (101.7, 102.1±13.65 MPa), PC (165.2, 160±34.7 MPa), ECAD (437.2, 416.1±50.1 MPa), ZrCAD (804.2, 800.8±64.47 MPa) and VYZ (792.7, 807±100.7 MPa). The type of ceramic influenced the flexural strength values (P=0.0001). The ceramics ECADa, e-max ZrCADa and VYZa presented similar flexural strength values which were significantly higher than the other groups (PCb and VM IIb), which were similar statistically between them (Dunn's test). The hypothesis was accepted. CONCLUSION: The polycrystalline ceramics (Y-TZP) should be material chosen for make FPDs because of their higher flexural strength values.

Buso L; Oliveira-Júnior OB; Hiroshi Fujiy F; Leão Lombardo GH; Ramalho Sarmento H; Campos F; Assunção Souza RO

2011-06-01

169

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

Energy Technology Data Exchange (ETDEWEB)

Results from diffusion studies of different impurities in biaxially strained Si and Si{sub 1-x}Ge {sub x} for low x-values will be presented. The structures are all molecular-beam epitaxy (MBE) grown on strain-relaxed Si{sub 1-x}Ge {sub 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.

Larsen, Arne Nylandsted [Institute of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C (Denmark)]. E-mail: anl@phys.au.dk; Zangenberg, Nikolaj [Institute of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C (Denmark); Fage-Pedersen, Jacob [Institute of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C (Denmark)

2005-12-05

170

Fracture and Fatigue Characterization of Aircraft Structural Materials under Biaxial Loading.  

Science.gov (United States)

A general fracture mechanics analysis was performed to examine the influence of biaxial applied loads on the mechanical state of the body. The geometries examined were the single crack and two coplanar cracks with an arbitrary orientation and the cracked ...

D. L. Jones J. Eftis

1981-01-01

171

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

Science.gov (United States)

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

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

2000-01-01

172

The impact of hydrofluoric acid etching followed by unfilled resin on the biaxial strength of a glass-ceramic.  

UK PubMed Central (United Kingdom)

OBJECTIVES: To evaluate the null hypotheses that hydrofluoric (HF) acid etching time would neither decrease the biaxial flexural strength of a glass-based veneering ceramic nor enhance it after silane and unfilled resin (UR) applications. METHODS: Disc-shaped IPS e.max ZirPress specimens were allocated into 12 groups: G1-control (no-etching), G2-30s, G3-60s, G4-90s, G5-120s, G6-60s+60s. Groups (G7-G12) were treated in the same fashion as G1-G6, but followed by silane and UR applications. Surface morphology and roughness (Ra and Rq) of the ceramics were assessed by means of scanning electron microscopy (SEM) and profilometry, respectively. Flexural strength was determined by biaxial testing. Data were analyzed by two-way ANOVA and the Sidak test (?=0.05). Weibull statistics were estimated and finite element analysis (FEA) was carried out to verify the stress concentration end areas of fracture. RESULTS: The interaction (etching time vs. surface treatment) was significant for Ra (p=0.008) and Rq (0.0075). Resin-treated groups presented significantly lower Ra and Rq than non-treated groups, except for the 60s group (p<0.005). SEM revealed that etching affected the ceramic microstructure and that the UR was able to penetrate into the irregularities. A significant effect of etching time (p=0.029) on flexural strength was seen. G7-G12 presented higher strength than G1-G6 (p<0.0001). None of experimental groups failed to show 95% confidence intervals of ?0 and m overlapped. FEA showed lower stress concentration after resin treatment. SIGNIFICANCE: HF acid etching time did not show a damaging effect on the ceramic flexural strength. Moreover, the flexural strength could be enhanced after UR treatment.

Posritong S; Borges AL; Chu TM; Eckert GJ; Bottino MA; Bottino MC

2013-09-01

173

Fabrication of biaxially oriented YBCO on (00{ell}) biaxially oriented yttria-stabilized-zirconia on polycrystalline substrates  

Energy Technology Data Exchange (ETDEWEB)

Ion-assisted, ion-beam sputter deposition is used to obtain (00l) biaxially oriented films of cubic yttria-stabilized-zirconia (YSZ) on polycrystalline metal substrates. Yttrium-barium-copper-oxide (YBCO) is then heteroepitaxially-pulse-laser deposited onto the YSZ. Phi scans of the films show the full-width-half maxima of the YSZ (202) and the YBCO(103) reflections to be 14{degree} and 10{degree} respectively. Our best dc transport critical current density measurement for the YBCO is 800,000 A/cm{sup 2} at 75K and 0T. At 75K, the total dc transport current in a 1 cm wide YBCO film is 23 A.

Arendt, P.; Foltyn, S.; Wu, Xin Di [and others

1994-07-01

174

Combined biaxial and uniaxial mechanical characterization of prosthetic meshes in a rabbit model.  

Science.gov (United States)

The present experimental study is aimed at a combined uniaxial and biaxial mechanical characterization of the deformation behavior of two types of prosthetic meshes, SPMM (heavy-weight) and Gynemesh M (light-weight, partly absorbable), after integration in the host tissue. Explants from a full-thickness-abdominal-wall-defect-rabbit-model were tested in the two loading conditions. Corresponding protocols and data analysis procedures for biaxial inflation tests and uniaxial tensile tests were developed. Biaxial responses were observed to be by factor 2-4 stiffer compared to corresponding uniaxial experiments, depending on the material tested. In biaxial loading conditions, SPMM explants were stiffest. Gynemesh M explants and native tissue were similarly compliant at low membrane tensions (5N/cm), there were distinct differences in the stiffness of the three groups, SPMM explants being the stiffest, followed by Gynemesh M explants and native tissue being the most compliant. In uniaxial loading conditions, the two explants were similarly stiff and distinctly stiffer than native tissue at low membrane tensions (5N/cm), differences between all groups vanished. Biaxial and uniaxial tests yield different results with respect to the mechanical behavior of mesh explants. These findings demonstrate that an evaluation of the mechanical biocompatibility of prosthetic meshes should be based on an experimental configuration (uniaxial or biaxial tension) which reproduces the expected in vivo conditions of mechanical loading and deformation. PMID:23672949

Röhrnbauer, B; Ozog, Y; Egger, J; Werbrouck, E; Deprest, J; Mazza, E

2013-05-11

175

Shear wave transducer for stress measurements in boreholes  

Energy Technology Data Exchange (ETDEWEB)

A technique and apparatus for estimating in situ stresses by measuring stress-induced velocity anisotropy around a borehole. Two sets each of radially and tangentially polarized transducers are placed inside the hole with displacement directions either parallel or perpendicular to the principal stress directions. With this configuration, relative travel times are measured by both a pulsed phase-locked loop technique and a cross correlation of digitized waveforms. The biaxial velocity data is used to back-calculate the applied stress.

Mao, Nai-Hsien (Castro Valley, CA)

1987-01-01

176

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)

2001-01-01

177

Electret properties of biaxially stretched polypropylene films containing various additives  

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-02-07

178

Electret properties of biaxially stretched polypropylene films containing various additives  

International Nuclear Information System (INIS)

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

2006-02-07

179

Vibration and buckling of square plates with square holes subjected to biaxial and shear loads  

Energy Technology Data Exchange (ETDEWEB)

The finite element method of analysis is used to determine the elastic buckling loads and natural circular frequencies of flat square plates. The square plates contain centrally located square holes that vary in size. The plates are subjected to inplane biaxial compression, tensile loads and uniform shear. In all cases the load is distributed uniformly along the simply supported or clamped outer edges. The finite element used for calculating the inplane stiffness matrix is based on an assumed strain rather than displacement field, and is rectangular in shape. The out of plane finite element used is the nonconforming rectangular bending element having a total of twelve degrees of freedom, three at each of the four corner nodes. Square plates with centrally located holes are initially subjected to inplane biaxial compression, and the effect of this load on the natural frequency is examined for different sizes of hole. Similar analysis was carried out when inplane biaxial tension and uniform shear was applied. For both cases of biaxial compression and shear, the natural frequency decreased towards zero, as the applied force increased towards the elastic buckling load. When biaxial tension was applied the natural frequency increased with increasing tensile loads.

Sabir, A.B.; Davies, G.T. [Univ. of Wales, Cardiff (United Kingdom). Div. of Structural Engineering

1996-11-01

180

Thermal stress in diamond films  

Energy Technology Data Exchange (ETDEWEB)

Residual stress in polycrystalline diamond films deposited from a DC arc plasma on ten different substrate materials (SiO{sub 2}, Si, SiC, Mo, Cu, Ni, Fe-Ni alloy, WC-Co and steel) was measured using micro Raman spectroscopy and X-ray diffraction technique. To improve adhesion some metals were precoated with a thin buffer layer of tungsten. The measured stress correlates with expected thermal stress originated from a mismatch in coefficients of thermal expansion (CTE) for diamond and substrate materials. The highest compressive stress at room temperature {sigma} = -11.4 GPa has been found at Ni substrate, and it increased to -14.3 GPa at T=78 K, while the stress was strongly relaxed at copper because of its plasticity. The stress values determined from Raman spectra using a biaxial stress model are in good agreement with data obtained from X-ray diffraction.

Ralchenko, V.G.; Obraztsova, E.D.; Korotoushenko, K.G. [Institute of General Physics, Moscow (Russian Federation)] [and others

1995-12-31

 
 
 
 
181

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

International Nuclear Information System (INIS)

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

2011-06-01

182

Biaxial CdTe/CaF2 films growth on amorphous surface  

International Nuclear Information System (INIS)

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

2009-10-30

183

Biaxial microincision cataract surgery versus conventional coaxial cataract surgery: metaanalysis of randomized controlled trials.  

UK PubMed Central (United Kingdom)

A comprehensive literature search of Cochrane Library, PubMed, and Embase was performed to identify relevant prospective randomized controlled trials (RCTs) comparing biaxial microincision cataract surgery (MICS) and conventional coaxial phacoemulsification. A metaanalysis was performed on the following outcome measures: effective phacoemulsification time (EPT), phacoemulsification power (%), corrected distance visual acuity (CDVA), surgically induced astigmatism (SIA), laser flare photometry value, percentage of endothelial cell loss, change in central corneal thickness (CCT), and complications. Eleven RCTs describing a total of 1064 eyes were identified. There were no significant differences between the techniques in CDVA, mean percentage of endothelial cell loss, laser flare photometry value, CCT change, and intraoperative and postoperative complications. However, EPT was statistically significantly shorter and the mean phaco power was statistically significantly lower in the biaxial group than in the coaxial group, and biaxial MICS induced less SIA. Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Yu JG; Zhao YE; Shi JL; Ye T; Jin N; Wang QM; Feng YF

2012-05-01

184

Biaxial microincision cataract surgery versus conventional coaxial cataract surgery: metaanalysis of randomized controlled trials.  

Science.gov (United States)

A comprehensive literature search of Cochrane Library, PubMed, and Embase was performed to identify relevant prospective randomized controlled trials (RCTs) comparing biaxial microincision cataract surgery (MICS) and conventional coaxial phacoemulsification. A metaanalysis was performed on the following outcome measures: effective phacoemulsification time (EPT), phacoemulsification power (%), corrected distance visual acuity (CDVA), surgically induced astigmatism (SIA), laser flare photometry value, percentage of endothelial cell loss, change in central corneal thickness (CCT), and complications. Eleven RCTs describing a total of 1064 eyes were identified. There were no significant differences between the techniques in CDVA, mean percentage of endothelial cell loss, laser flare photometry value, CCT change, and intraoperative and postoperative complications. However, EPT was statistically significantly shorter and the mean phaco power was statistically significantly lower in the biaxial group than in the coaxial group, and biaxial MICS induced less SIA. Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned. PMID:22424804

Yu, Ji-guo; Zhao, Yun-e; Shi, Jie-liang; Ye, Ting; Jin, Nan; Wang, Qin-mei; Feng, Yi-fan

2012-03-16

185

Enhancement by polydispersity of the biaxial nematic phase in a mixture of hard rods and plates  

CERN Multimedia

The phase diagram of a polydisperse mixture of uniaxial rod-like and plate-like hard parallelepipeds is determined for aspect ratios $\\kappa=5$ and 15. All particles have equal volume and polydispersity is introduced in a highly symmetric way. The corresponding binary mixture is known to have a biaxial phase for $\\kappa=15$, but to be unstable against demixing into two uniaxial nematics for $\\kappa=5$. We find that the phase diagram for $\\kappa=15$ is qualitatively similar to that of the binary mixture, regardless the amount of polydispersity, while for $\\kappa=5$ a sufficient amount of polydispersity stabilizes the biaxial phase. This provides some clues for the design of an experiment in which this long searched biaxial phase could be observed.

Martínez-Raton, Y; Martinez-Raton, Yuri; Cuesta, Jose A.

2002-01-01

186

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

CERN Multimedia

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

Wittkowski, Raphael

2011-01-01

187

The fabrication and high temperature stability of biaxially textured Ni tape by ion beam structure modification method  

Energy Technology Data Exchange (ETDEWEB)

For the conventional rolling assisted biaxially textured metallic substrate (RABiTS) process, a large degree of cold rolling deformation and a subsequent high temperature annealing procedure are required to obtain adequately biaxially textured Ni tape. Recently, we have reported a newly developed process, named as ion beam structure modification (ISM), for fabricating biaxially textured Ni tape by use of low energy argon ion beam bombardment. In this paper, the biaxial texture of ISM processed Ni tape and its thermal stability at high temperatures are investigated. Results show that Ni tape processed under optimum ISM conditions, the (2 0 0) rocking curve FWHM is less than 5.7 deg. , and the (1 1 1) phi-scan FWHM is less than 7.5 deg. . High temperature annealing does not impair the biaxial-texture already developed in ISM processed Ni foils, although ISMs should not be regarded as a complete equilibrium process.

Wu, K.; Wang, S.S.; Meng, J.; Han, Z

2004-10-01

188

Phase transitions and domain stabilities in biaxially strained (001) SrTiO3 epitaxial thin films  

Energy Technology Data Exchange (ETDEWEB)

We applied phase-field approach to investigate both ferroelectric and antiferrodistortive (AFD) transitions in (001) SrTiO3 epitaxial thin films that are strained biaxially. A domain/phase stability diagram of 'misfit strain-temperature' was constructed for equi-biaxially strained (001) SrTiO3 thin films, which exhibits significant differences from previous diagrams obtained using thermodynamic analysis of a single domain. For unequi-biaxially strained (001) SrTiO3 thin films, 'misfit strain-misfit strain' domain stability diagrams at several representative temperatures were obtained. The predicted phase transitions, domain stabilities, and domain structures in three different SrTiO3 thin films under either equi-biaxial or unequi-biaxial strains agree well with experimental observations.

Sheng, Guang; Li, Yulan; Zhang , J.X.; Choudhury, S.; Jia, Q.X.; Gopalan, Venkatraman; Schlom, Darrell G.; Liu, Z. K.; Chen , L.Q.

2010-10-15

189

Combined biaxial and uniaxial mechanical characterization of prosthetic meshes in a rabbit model.  

UK PubMed Central (United Kingdom)

The present experimental study is aimed at a combined uniaxial and biaxial mechanical characterization of the deformation behavior of two types of prosthetic meshes, SPMM (heavy-weight) and Gynemesh M (light-weight, partly absorbable), after integration in the host tissue. Explants from a full-thickness-abdominal-wall-defect-rabbit-model were tested in the two loading conditions. Corresponding protocols and data analysis procedures for biaxial inflation tests and uniaxial tensile tests were developed. Biaxial responses were observed to be by factor 2-4 stiffer compared to corresponding uniaxial experiments, depending on the material tested. In biaxial loading conditions, SPMM explants were stiffest. Gynemesh M explants and native tissue were similarly compliant at low membrane tensions (<5N/cm) (abdominal wall: 40±23N/cm, Gynemesh M: 59±44N/cm, SPMM: 145±36N/cm). At high membrane tensions (>5N/cm), there were distinct differences in the stiffness of the three groups, SPMM explants being the stiffest, followed by Gynemesh M explants and native tissue being the most compliant. In uniaxial loading conditions, the two explants were similarly stiff and distinctly stiffer than native tissue at low membrane tensions (<5N/cm) (abdominal wall: 9±1N/cm, Gynemesh M: 21±5N/cm, and SPMM: 24±5N/cm). At high membrane tension (>5N/cm), differences between all groups vanished. Biaxial and uniaxial tests yield different results with respect to the mechanical behavior of mesh explants. These findings demonstrate that an evaluation of the mechanical biocompatibility of prosthetic meshes should be based on an experimental configuration (uniaxial or biaxial tension) which reproduces the expected in vivo conditions of mechanical loading and deformation.

Röhrnbauer B; Ozog Y; Egger J; Werbrouck E; Deprest J; Mazza E

2013-06-01

190

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

1982-01-01

191

Biaxial tensile strain effects on photoluminescence of different orientated Ge wafers  

Science.gov (United States)

The enhanced photoluminescence of direct transition is observed on (100), (110), and (111) Ge under biaxial tensile strain. The enhancement is caused by the increase in electron population in the ? valley. The shrinkage of energy difference between the lowest L valleys and the ? valley is responsible to the population increase on (100) and (110) Ge. For (111) Ge, the energy difference increases under biaxial tensile strain but the strain decreases energy difference between the electron quasi-Fermi level and the ? valley due to the small density of state of the lowest L valleys, and thus enhances direct recombination.

Lan, H.-S.; Chan, S.-T.; Cheng, T.-H.; Chen, C.-Y.; Jan, S.-R.; Liu, C. W.

2011-03-01

192

ANALYTICAL MODEL OF SURFACE POTENTIAL AND THRESHOLD VOLTAGE OF BIAXIAL STRAINED SILICON NMOSFET INCLUDING QME  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper physics based analytical model for threshold voltage of nanoscale biaxial strained nMOSFET has been presented. The maximum depletion depth and surface potential in biaxial strained–Si nMOSFET is determined, taking into account both the quantum mechanical effects (QME) and effects of strain in inversion charge sheet. The results show that a significant decrease in threshold voltage occurs with the increase in the germanium content in the silicon germanium layer. The results have been compared with the published data and the effect of variation of channel doping concentration has been examined.

Shiromani Balmukund Rahi; Garima Joshi

2012-01-01

193

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-11-01

194

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

Energy Technology Data Exchange (ETDEWEB)

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.

Jau, W.C.; White, R.N.; Gergely, P.

1982-09-01

195

Caracterización del ablandamiento de los elastómeroscuando son sometidos a esfuerzos biaxiales  

Directory of Open Access Journals (Sweden)

Full Text Available En este artículo se emplea el modelo mecanístico desarrollado por Elías-Zúñiga y Beatty para estudiar el ablandamiento, conocido como el efecto de Mullin, en materiales elastoméricos sometidos a estados de esfuerzos biaxiales. En particular, se estudia el efecto de ablandamiento que experimenta el material durante el proceso de inflado y desinflado de globos. Además, se analizan datos experimentales obtenidos en compresión uniaxial simple ya que este estado de carga es cinemáticamente equivalente a elongaciones biaxiales. En la parte final del presente trabajo, se hace una comparación entre los resultados obtenidos mediante el empleo del modelo propuesto y los datos experimentales disponibles en la literatura

Alex Elías Zúñiga; Conrado Rosales Torres

2006-01-01

196

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

Science.gov (United States)

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.

Liu, Jianguang; Wang, Zhongjin; Meng, Qingyuan

2012-04-01

197

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

Science.gov (United States)

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.

Li, Chun-Ran; Li, Yong-Feng; Yao, Bin; Yang, Gang; Ding, Zhan-Hui; Deng, Rui; Liu, Lei

2013-11-01

198

Determination of flow stress by the hydraulic bulge test  

Directory of Open Access Journals (Sweden)

Full Text Available In sheet metal forming operations the mechanical properties of the sheet metal (stress-strain curve, flow stress) greatly influence metal flow and product quality. Accurate determination of the stress-strain relationship is important in process simulation by finite element method. In this paper the sheet thickness gradation in different points of the hemisphere formed in the bulge test is analysed, both theoretically and experimentally. A precise determination of sheet thickness at the pole is very important in the precise determination of stress-strain relationship. The use of the hydraulic bulge test for estimation of flow stress under biaxial stress-strain state is discussed.

Slota, J.; Spišák, E.

2008-01-01

199

Electronic structure and optical properties of CuAlO2 under biaxial strain.  

Science.gov (United States)

An ab initio calculation has been carried out to investigate the biaxial strain ( - 10.71% 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 CuAlO(2). PMID:22551761

Ghosh, C K; Sarkar, D; Mitra, M K; Chattopadhyay, K K

2012-05-03

200

DIC-aided biaxial fatigue tests of a 304L steel  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 C...

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

 
 
 
 
201

Evidence for shear-induced biaxiality in L? lecithins close to solid surfaces  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Optical studies of shear-oriented water-lecithin multilayers were performed in the L? phase of egg and di-palmitoyl lecithins. The samples appeared biaxial with the plane of the two principal optic axes parallel to the direction of shear. Since L? phases are known to be uniaxial in the bulk, we attr...

Micciancio, S.; Rondelez, F.

202

Peripheral (punching) shear strength of biaxially tensioned reinforced concrete wall elements  

International Nuclear Information System (INIS)

Results are presented for the peripheral shear strength of orthogonally reinforced concrete wall elements carrying various levels of biaxial tension in combination with the punching shear force. This loading condition occurs in containments and other nuclear structures at attachments to the walls and at penetrations through the walls. (orig./HP).

1981-08-21

203

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

Energy Technology Data Exchange (ETDEWEB)

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

Pennell, W.E.; Bass, B.R.; Bryson, J.W.; McAfee, W.J.; Theiss, T.J.; Rao, M.C.

1993-12-01

204

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

International Nuclear Information System (INIS)

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

1993-01-01

205

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

Energy Technology Data Exchange (ETDEWEB)

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

Pennell, W.E.; Bass, B.R.; Bryson, J.W.; McAfee, W.J.; Theiss, T.J.; Rao, M.C.

1994-04-01

206

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

Directory of Open Access Journals (Sweden)

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.

Taweep Chaisomphob; Suapphong Kritsanawonghong; Chayanon Hansapinyo

2003-01-01

207

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

Directory of Open Access Journals (Sweden)

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

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

2010-01-01

208

AN UPDATE ON BIAXIAL THERMAL CREEP OF VANADIUM ALLOYS  

Energy Technology Data Exchange (ETDEWEB)

A study of the thermal creep properties of two vanadium alloys was 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 effective (Von Mises) yield strength. Specimens were fabricated from V-4Cr-4Ti (Heat No. 832665) and a V-3Fe-4Ti alloy. The samples were heated to 650, 700, 725, and 800 degrees C in an ultra-high vacuum furnace and periodically removed to measure the change in tube outer diameter with a high-precision laser profilometer. The normalized minimum creep rate was found to be power-law dependent on the modulus compensated applied stress. The value of the stress exponent varied with the applied stress. At normalized stresses ranging from 0.002 to 0.008 the stress exponent was about 4 and the activation energy was about 300 kJ/mole, which is quite close to the activation energy for self-diffusion in pure vanadium. These results suggest that the predominant mechanism of creep in this regime is climb-assisted dislocation motion. At lower stresses the value of the stress exponent is near unity suggesting that viscous creep mechanisms such as Coble creep or grain boundary sliding may be operative, but the data are too sparse to be conclusive. The reported creep rates from uniaxial tests [1] in vacuum are several times higher than the creep rates measured here. This is probably due to the larger interstitial oxygen concentration of the creep tubing (699 wppm) compared to the sheet stock (310 wppm) used for tensile specimen fabrication. Finally, the creep strength of V-4Cr-4Ti at 700 and 800 degrees C was superior to the V-3Fe-4Ti alloy.

Kurtz, Richard J.; Ermi, August M.

2002-09-01

209

Molecular model of biaxial ordering in nematic liquid crystals composed of flat molecules with four mesogenic groups.  

UK PubMed Central (United Kingdom)

Relative stability of uniaxial and biaxial nematic phases is analyzed in a model nematic liquid crystal composed of flat molecules of C2h symmetry with four mesogenic groups rigidly linked to the same center. The generalized effective quadrupole mean-field potential is proposed and its constants are evaluated numerically for the pair intermolecular potential based on Gay-Berne interaction between mesogenic groups. The dependencies of the constants on molecular shape parameters are systematically analyzed. Order parameters of the uniaxial and biaxial nematic phases are evaluated by direct minimization of the free energy at different temperatures. The corresponding phase diagrams are obtained enabling one to study the effects of molecular model parameters on the stability regions of uniaxial and biaxial phases. The results are used to clarify the nature of experimentally observed biaxial ordering in nematic liquid crystals composed of tetrapode molecules with the same symmetry.

Gorkunov MV; Osipov MA; Kocot A; Vij JK

2010-06-01

210

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

CERN Document Server

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.

Li Peng; Mazumder, J

2003-01-01

211

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)

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)

Aubin, V

2001-11-15

212

Preliminary assessment of the effects of biaxial loading on reactor pressure vessel structural-integrity-assessment technology  

Energy Technology Data Exchange (ETDEWEB)

Effects of biaxial loading on shallow-flaw fracture toughness were studied to determine potential impact on structural integrity assessment of a reactor pressure vessel (RPV) under pressurized thermal shock (PTS) transient loading and pressure-temperature (PT) loading produced by reactor heatup and cooldown transients. Biaxial shallow-flaw fracture-toughness tests results were also used to determine the parameter controlling fracture in the transition temperature range, and to develop a related dual-parameter fracture-toughness correlation. Shallow-flaw and biaxial loading effects were found to reduce the conditional probability of crack initiation by a factor of nine when the shallow-flaw fracture-toughness K{sub Jc} data set, with biaxial-loading effects adjustments, was substituted in place of ASME Code K{sub Ic} data set in PTS analyses. Biaxial loading was found to reduce the shallow-flaw fracture toughness of RPV steel such that the lower-bound curve was located between ASME K{sub Ic} and K{sub IR} curves. This is relevant to future development of P-T curve analysis procedures. Fracture in shallow-flaw biaxial samples tested in the lower transition temperature range was shown to be strain controlled. A strain-based dual-parameter fracture-toughness correlation was developed and shown to be capable of predicting the effect of crack-tip constraint on fracture toughness for strain-controlled fracture.

Pennell, W.E.; Bass, B.R.; Bryson, J.W.; Dickson, T.L.; McAfee, W.J.; Merkle, J.G.

1996-04-01

213

Preliminary assessment of the effects of biaxial loading on reactor pressure vessel structural-integrity-assessment technology  

International Nuclear Information System (INIS)

Effects of biaxial loading on shallow-flaw fracture toughness were studied to determine potential impact on structural integrity assessment of a reactor pressure vessel (RPV) under pressurized thermal shock (PTS) transient loading and pressure-temperature (PT) loading produced by reactor heatup and cooldown transients. Biaxial shallow-flaw fracture-toughness tests results were also used to determine the parameter controlling fracture in the transition temperature range, and to develop a related dual-parameter fracture-toughness correlation. Shallow-flaw and biaxial loading effects were found to reduce the conditional probability of crack initiation by a factor of nine when the shallow-flaw fracture-toughness KJc data set, with biaxial-loading effects adjustments, was substituted in place of ASME Code KIc data set in PTS analyses. Biaxial loading was found to reduce the shallow-flaw fracture toughness of RPV steel such that the lower-bound curve was located between ASME KIc and KIR curves. This is relevant to future development of P-T curve analysis procedures. Fracture in shallow-flaw biaxial samples tested in the lower transition temperature range was shown to be strain controlled. A strain-based dual-parameter fracture-toughness correlation was developed and shown to be capable of predicting the effect of crack-tip constraint on fracture toughness for strain-controlled fracture

1996-01-01

214

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

UK PubMed Central (United Kingdom)

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.

Goto M; Takezoe H; Ishikawa K

2010-02-01

215

Behaviour of reinforced concrete column under biaxial cyclic loading—state of the art  

Science.gov (United States)

The cyclic behaviour of reinforced concrete columns has been object of many experimental studies in the last years, mostly focused on the unidirectional loading of columns under constant axial load conditions. In this research work, the existing test on reinforced concrete (RC) columns under biaxial load has been reviewed, underlying their main findings. In general, the experimental results show that the RC columns' response is highly dependent on the loading pattern, and the biaxial loading induces a decrease in the maximum strength and anticipates each damage state. Thus, in columns where demands are expected with large moments in both directions, specific detailing should be provided in their critical regions in order to improve the columns' performance and avoid premature failure.

Rodrigues, Hugo; Varum, Humberto; Arêde, Antonio; Costa, Aníbal G.

2013-12-01

216

Opening up complete photonic bandgaps in three-dimensional photonic crystals consisting of biaxial dielectric spheres.  

UK PubMed Central (United Kingdom)

In this paper, the scattering matrix of sphere with dielectric biaxial anisotropy is obtained exactly within the framework of the extended Mie theory. By incorporating the scattering matrix into the multiple scattering method, we study theoretically the photonic band structure of three dimensional photonic crystals consisting of biaxial dielectric spheres. Our results demonstrate that complete photonic bandgaps can be found in both fcc and sc lattice structures, which are absent in photonic crystals composed of isotropic dielectric spheres. Moreover we have compared our results with those coming from the photonic crystals consisting of the uniaxially birefringent dielectric spheres. It is found that because of the enhancement of the anisotropy, the degeneracy is lifted further, resulting in two neighboring photonic bandgaps, the lower one is complete while the upper one is partial existing only in some special regions of the first Brillouin zone.

Liu S; Lin Z

2006-06-01

217

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.

2013-01-01

218

The significance of biaxial loading on the fracture performance of a pressure vessel steel  

International Nuclear Information System (INIS)

An extensive program of tests on the nuclear pressure vessel steel A533B has been carried out under uniaxial bend and tension and biaxial tension. These tests have been performed at temperatures above the ductile/brittle transition (+ 70 degrees C) and below the transition (-130 degrees C). The Nuclear Installations Inspectorate are now sponsoring a series of tests at The Welding Institute (TWI) examining the behavior of specimens under uniaxial and biaxial tension in the transition region. This paper examines the first results from this program and compares the data with upper and lower shelf data obtained previously. In particular, the Level 2 Fracture Assessment procedure from the revised BSI PD6493 document is employed and its accuracy assessed against the test results.

1991-01-01

219

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

CERN Document Server

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

Longa, L; Longa, Lech; Wydro, Thomas

2007-01-01

220

Exploiting design freedom in biaxial dielectrics to enable spatially overlapping optical instruments.  

UK PubMed Central (United Kingdom)

The optical behavior of gradient biaxial dielectrics has not been widely explored in the literature due to their complicated nature, but the extra degrees of freedom in the index tensor have the potential of yielding useful optical instruments which are otherwise unachievable. In this work, a design method is described in detail which allows one to combine the behavior of up to four totally independent isotropic optical instruments in an overlapping region of space. This is non-trivial because of the mixing of the index tensor elements in the Hamiltonians; previously known methods only handled uniaxial dielectrics (where only two independent isotropic optical functions could overlap). The biaxial method introduced also allows three-dimensional multi-faced Janus devices to be designed; these are worked out in an example of what is possible to design with the method.

Akbarzadeh A; Qiu CW; Danner AJ

2013-01-01

 
 
 
 
221

Exploiting design freedom in biaxial dielectrics to enable spatially overlapping optical instruments  

Science.gov (United States)

The optical behavior of gradient biaxial dielectrics has not been widely explored in the literature due to their complicated nature, but the extra degrees of freedom in the index tensor have the potential of yielding useful optical instruments which are otherwise unachievable. In this work, a design method is described in detail which allows one to combine the behavior of up to four totally independent isotropic optical instruments in an overlapping region of space. This is non-trivial because of the mixing of the index tensor elements in the Hamiltonians; previously known methods only handled uniaxial dielectrics (where only two independent isotropic optical functions could overlap). The biaxial method introduced also allows three-dimensional multi-faced Janus devices to be designed; these are worked out in an example of what is possible to design with the method.

Akbarzadeh, Alireza; Qiu, Cheng-Wei; Danner, Aaron J.

2013-01-01

222

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

International Nuclear Information System (INIS)

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

2010-06-01

223

Development of fibroblast-seeded collagen gels under planar biaxial mechanical constraints: a biomechanical study.  

UK PubMed Central (United Kingdom)

Prior studies indicated that mechanical loading influences cell turnover and matrix remodeling in tissues, suggesting that mechanical stimuli can play an active role in engineering artificial tissues. While most tissue culture studies focus on influence of uniaxial loading or constraints, effects of multi-axial loading or constraints on tissue development are far from clear. In this study, we examined the biaxial mechanical properties of fibroblast-seeded collagen gels cultured under four different mechanical constraints for 6 days: free-floating, equibiaxial stretching (with three different stretch ratios), strip-biaxial stretching, and uniaxial stretching. Passive mechanical behavior of the cell-seeded gels was also examined after decellularization. A continuum-based two-dimensional Fung model was used to quantify the mechanical behavior of the gel. Based on the model, the value of stored strain energy and the ratio of stiffness in the stretching directions were calculated at prescribed strains for each gel, and statistical comparisons were made among the gels cultured under the various mechanical constraints. Results showed that gels cultured under the free-floating and equibiaxial stretching conditions exhibited a nearly isotropic mechanical behavior, while gels cultured under the strip-biaxial and uniaxial stretching conditions developed a significant degree of mechanical anisotropy. In particular, gels cultured under the equibiaxial stretching condition with a greater stretch ratio appeared to be stiffer than those with a smaller stretch ratio. Also, a decellularized gel was stiffer than its non-decellularized counterpart. Finally, the retained mechanical anisotropy in gels cultured under the strip-biaxial stretching and uniaxial stretching conditions after cell removal reflected an irreversible matrix remodeling.

Hu JJ; Liu YC; Chen GW; Wang MX; Lee PY

2013-10-01

224

Development of fibroblast-seeded collagen gels under planar biaxial mechanical constraints: a biomechanical study.  

Science.gov (United States)

Prior studies indicated that mechanical loading influences cell turnover and matrix remodeling in tissues, suggesting that mechanical stimuli can play an active role in engineering artificial tissues. While most tissue culture studies focus on influence of uniaxial loading or constraints, effects of multi-axial loading or constraints on tissue development are far from clear. In this study, we examined the biaxial mechanical properties of fibroblast-seeded collagen gels cultured under four different mechanical constraints for 6 days: free-floating, equibiaxial stretching (with three different stretch ratios), strip-biaxial stretching, and uniaxial stretching. Passive mechanical behavior of the cell-seeded gels was also examined after decellularization. A continuum-based two-dimensional Fung model was used to quantify the mechanical behavior of the gel. Based on the model, the value of stored strain energy and the ratio of stiffness in the stretching directions were calculated at prescribed strains for each gel, and statistical comparisons were made among the gels cultured under the various mechanical constraints. Results showed that gels cultured under the free-floating and equibiaxial stretching conditions exhibited a nearly isotropic mechanical behavior, while gels cultured under the strip-biaxial and uniaxial stretching conditions developed a significant degree of mechanical anisotropy. In particular, gels cultured under the equibiaxial stretching condition with a greater stretch ratio appeared to be stiffer than those with a smaller stretch ratio. Also, a decellularized gel was stiffer than its non-decellularized counterpart. Finally, the retained mechanical anisotropy in gels cultured under the strip-biaxial stretching and uniaxial stretching conditions after cell removal reflected an irreversible matrix remodeling. PMID:23096240

Hu, Jin-Jia; Liu, Yen-Ching; Chen, Guan-Wen; Wang, Mei-Xuan; Lee, Pei-Yuan

2012-10-25

225

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)

2005-01-01

226

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Advances in all-ceramic systems have established predictable means of providing metal-free aesthetic and biocompatible materials. These materials must have sufficient strength to be a practical treatment alternative for the fabrication of crowns and fixed partial dentures. OBJECTIVES: The aim of this study was to compare the biaxial flexural strength of three core ceramic materials. MATERIAL AND METHODS: Three groups of 10 disc-shaped specimens (16 mm diameter x 1.2 mm th (more) ickness - 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

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

2010-12-01

227

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

Science.gov (United States)

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.

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

2011-10-01

228

Biaxial texture development in the ion beam assisted deposition of magnesium oxide  

Science.gov (United States)

Low-energy ion-beam irradiation (magnesium oxide (MgO), has been successfully used as a biaxially textured template film for the heteroepitaxial deposition of many materials with texture dependent properties like high temperature superconductors, tunable microwave materials, and ferroelectrics. Here, we present data on the initial nucleation of biaxial crystallographic texture in this model system using an in situ quartz crystal microbalance (QCM) substrate combined with in situ reflected high-energy electron diffraction (RHEED). Correlation of mass uptake with the RHEED images of the growing surface shows that the development of crystallographic biaxial texture in this material system occurs suddenly as the initially polycrystalline MgO films reaches a critical film thickness of 2 nm. This texture continues to improve during subsequent growth. A simple model shows that the effect is not due simply to coverage effects. We use a combination of in situ RHEED and ex situ transmission electron microscopy to further elucidate the mechanism of this sudden texture formation. We present a physical model to describe this behavior and explain the role of ion-to-atom arrival ratio and underlying nucleation surface on texture development.

Groves, James R.; Hammond, Robert H.; Matias, Vladimir; Depaula, Raymond F.; Stan, Liliana; Clemens, Bruce M.

2012-02-01

229

Biaxial texturing of inorganic photovoltaic thin films using low energy ion beam irradiation during growth  

Energy Technology Data Exchange (ETDEWEB)

We describe our efforts to control the grain boundary alignment in polycrystalline thin films of silicon by using a biaxially textured template layer of CaF{sub 2} for photovoltaic device applications. We have chosen CaF{sub 2} as a candidate material due to its close lattice match with silicon and its suitability as an ion beam assisted deposition (mAD) material. We show that the CaF{sub 2} aligns biaxially at a thickness of {approx}10 nm and, with the addition of an epitaxial CaF{sub 2} layer, has an in-plane texture of {approx}15{sup o}. Deposition of a subsequent layer of Si aligns on the template layer with an in-plane texture of 10.8{sup o}. The additional improvement of in-plane texture is similar to the behavior observed in more fully characterized IBAD materials systems. A germanium buffer layer is used to assist in the epitaxial deposition of Si on CaF{sub 2} template layers and single crystal substrates. These experiments confirm that an mAD template can be used to biaxially orient polycrystalline Si.

Groves, Jaes R [Los Alamos National Laboratory; De Paula, Raymond F [Los Alamos National Laboratory; Hayes, Garrett H [STANFORD UNIV.; Li, Joel B [STANFORD UNIV.; Hammond, Robert H [STANFORD UNIV.; Salleo, Alberto [STANFORD UNIV.; Clemens, Bruce M [STANFORD UNIV.

2010-01-01

230

Short-term and long-term behaviour of glass-fibre/matrix composite materials under monoaxial and biaxial loading as a function of the interface quality  

Energy Technology Data Exchange (ETDEWEB)

In order to reveal the essential role of the quality of the fiber/matrix interface in the definition of the final characteristics of glass/resin composite materials, the authors have investigated the behavior of composite samples, differing only by the interface quality, under the laws of loading, which are used most in industrial fields: (1) monoaxial tension with monitoring of acoustic emission spectra, (2) interlaminar shear, (3) crack initiation and crack growth in mode 1, (4) viscoelasticity in bending, and (5) biaxial monotonic tension, cyclic loading with increasing amplitude and dynamic fatigue. Biaxial tests were carried out on industrial tubing systems under internal pressure, the other tests on standard flat test pieces. In tension and interlaminar shear, the influence of fiber/matrix adhesion is not always very clear; it depends on the damage criterium and on the type of reinforcement used. The incidence of this parameter appears generally to be more pronounced through mode 1 fracture mechanics and viscoelasticity studies. Concerning the study of tubing systems, the level of sensitivity to the interface quality is dependent on the loading mode and the end of life criteria which have been chosen, weeping or limits of linearity. The results show that the nature of the fiber/matrix interface can strongly affect the mechanical behavior of composites. For instance, one can notice variations due to interface: (1) up to 50% on initiation and growth energies, (2) of more than 40% on the damping at glass transition temperature, (3) as high as 37% in term of circumferential stress at first damage, (4) the fatigue lifetime can be multiplied by ten.

Krawczak, P.; Pabiot, J. [Ecole des Mines, Douai (France). Dept. Technologie des Polymeres et Composites

1993-12-31

231

Hydration and radiation effects on the residual stress state of cortical bone.  

UK PubMed Central (United Kingdom)

The change in the biaxial residual stress state of hydroxyapatite crystals and collagen fibrillar structure in sections of bovine cortical bone has been investigated as a function of dehydration and radiation dose using combined small- and wide-angle X-ray scattering. It is shown that dehydration of the bone has a pronounced effect on the residual stress state of the crystalline phase, while the impact of radiation damage alone is less dramatic. In the initial hydrated state, a biaxial compressive stress of approximately -150MPa along the bone axis exists in the hydroxyapatite crystals. As water evaporates from the bone material, the stress state moves to a tensile state of approximately 100MPa. The collagen fibrillar structure is initially in a tensile residual stress state when the bone is hydrated and the state increases in magnitude slightly with dehydration. Radiation dose in continually hydrated samples also reduces the initial biaxial compressive stress magnitude in the hydroxyapatite phase, however the stress remains compressive. Radiation exposure alone does not appear to affect the stress state of the collagen fibrillar structure.

Tung PK; Mudie S; Daniels JE

2013-07-01

232

Ultimate strength property of concrete under triaxial compressive stresses  

International Nuclear Information System (INIS)

[en] The purpose was to examine the ultimate strength criteria of concrete under short-term multiaxial compressive stresses, as an aid to designing and analyzing the concrete structures subjected to multiaxial stresses, such as prestressed or reinforced concrete vessel structures. The ultimate strength of concrete under multiaxial stresses is a function of the state of stress. Therefore, the ultimate strength of concrete elements can be properly determined only by considering the interaction of the various components of the state of stress. The paper attempts to define such ultimate strength criteria as a function of the state of stress, valid for concrete under biaxial and triaxial compressive stress states. In mathematical description of ultimate strength criteria for concrete under combined states of stress, the ultimate strength under multiaxial compressive stresses was defined as the maximum load-carrying capacity of a test specimen. (orig./HP)

1983-01-01

233

Biaxial and failure properties of passive rat middle cerebral arteries.  

UK PubMed Central (United Kingdom)

Rodents are commonly used as test subjects in research on traumatic brain injury and stroke. However, study of rat cerebral vessel properties has largely been limited to pressure-diameter response within the physiological loading range. A more complete, multiaxial description is needed to guide experiments on rats and rat vessels and to appropriately translate findings to humans. Accordingly, we dissected twelve rat middle cerebral arteries (MCAs) and subjected them to combined inflation and axial stretch tests around physiological loading conditions while in a passive state. The MCAs were finally stretched axially to failure. Results showed that MCAs under physiological conditions were stiffer in the axial than circumferential direction by a mean (±standard deviation) factor of 1.72 (±0.73), similar to previously reported behavior of human cerebral arteries. However, the stiffness for both directions was lower in rat MCA than in human cerebral arteries (p<0.01). Failure stretch values were higher in rat MCA (1.35±0.08) than in human vessels (1.24±0.09) (p=0.003), but corresponding 1st Piola Kirchhoff stress values for rats (0.42±0.09 MPa) were considerably lower than those for humans (3.29±0.64 MPa) (p<0.001). These differences between human and rat vessel properties should be considered in rat models of human cerebrovascular injury and disease.

Bell ED; Kunjir RS; Monson KL

2013-01-01

234

Epitaxy of Germanium on Biaxially Textured Germanium and Calcium Fluoride Buffer Layers Through Nanoepitaxy  

Science.gov (United States)

The properties of biaxially textured semiconductor films deposited on nanostructured buffer layers with biaxial texture closely approximate the physical properties of single-crystal. This near single-crystal film can serve as substrates and offer significant cost saving benefits in applications such as displays and photovoltaic devices. This thesis provides results of the growth and characterization of Ge films nanoepitaxially deposited onto biaxially textured Ge (homo) and CaF2 (hetero) buffer layers. The film growth method was physical vapor deposition at normal and oblique angles of incidence. The characterization techniques used included atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray pole figure analyses. The Ge films nanoheteroepitaxialy deposited on CaF2 buffer layers were studied as a function of substrate temperature, the CaF2 morphology and orientation ([001] and [110]) to see the influence of these variables on the Ge films. Ge films deposited at 400°C on [001] oriented CaF2 buffer layer with ridge-like features resulted in nearly single-crystal Ge films of [001] orientation with 1.68° +/- 1° in-plane dispersion and a 1:1 main pole to twin pole ratio. Ge films deposited at 400°C onto a [110] oriented CaF2 buffer nanorods layer was found that the [110] Ge film has ˜20° in-plane dispersion but higher 6:1 twin ratio. The increased dispersion (˜20°) was attributed to the large dispersion in the CaF2 buffer layer that resulted from the low vapor incidence angle used during its deposition. The difference in the twin ratio of the Ge films was attributed to the difference in substrate morphology. The [110] oriented CaF2 buffer layer was composed of isolated nanorods while the [001] oriented CaF2 buffer layer had micron long well ordered ridge structures. According to the theory of nanoepitaxy the isolated nanorods in the [110] oriented buffer layer provided more strain relief to the Ge epilayer. This reduced the number of dislocations in the film resulting in a lower relative intensity of the twin poles (or higher main pole to twin pole ratio). The Ge films nanohomoepitaxialy deposited on Ge buffer layers on hydrogen terminated Si(100) were studied as a function of substrate temperature and deposition rate. In both the substrate temperature and deposition rate study the Ge buffer layer deposited at incident angle alpha=87°, temperature T=330°C, and rate=1.6 nm/min had {001} biaxial texture with the lowest in-plane dispersion (0.92° +/- 0.01°) and lowest relative intensity of twin poles (20:1). Ge films deposited on this buffer layer at 400°C had the lowest in-plane dispersion (0.83°), and a twin poles ratio (6:1). Ge films deposited directly on hydrogen terminated Si(100) at 400°C without Ge buffer layer had in-plane dispersion (0.47°) and twin ratio (1:1). The reduction in the relative intensity of the twin poles in the film deposited on the biaxial Ge buffer layer over the film deposited directly on H-Si(001) that has 4.2% Ge to Si lattice mismatch is attributed to the theory of strain relief in nanoepitaxy. The reduced dispersion and improved twin ratio in Ge films deposited on Ge buffer layer as compared to the nanoheteroepitaxial deposition of Ge on the [001] oriented CaF2 buffer layers indicated that the homoepitaxial deposition of Ge films on biaxially textured Ge buffer layers resulted in a better quality Ge film that is nearly single-crystal with twinning.

Snow, Patrick William

235

Influence of the deposition parameters on the biaxial alignment of MgO grown by unbalanced magnetron sputtering  

Science.gov (United States)

For many years magnesium oxide (MgO) played a key role in the research of buffer layers for high-temperature superconducting copper oxides. For buffer layers, not only the out-of-plane alignment has to be taken into account, but also the in-plane orientation, which is important. The goal of our experiments is to grow biaxially aligned layers, i.e. layers with both out-of-plane alignment and in-plane alignment. The biaxially aligned MgO layers are deposited by unbalanced magnetron sputtering on a non-textured substrate. By varying different deposition parameters (e.g. inclination angle, pressure, reactive gas flow, distance between target and substrate, etc.) it is possible to improve the biaxial alignment. MgO layers with a preferential [1 1 1] out-of-plane orientation and an in-plane alignment with a FWHM of 19.6° in ? and 7.8° in ? are observed.

Ghekiere, P.; Mahieu, S.; de Winter, G.; de Gryse, R.; Depla, D.

2004-11-01

236

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

Energy Technology Data Exchange (ETDEWEB)

Commercial applications of YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) superconducting cables require viable and scalable manufacturing processes. We have investigated the evolution of the biaxial alignment of yttria-stabilized zirconia (YSZ) buffer layers with increasing film thickness (50-900 nm) and report on a method of fabricating highly aligned YBCO tapes using a thin epitaxial YSZ buffer layer as template. The method employs magnetron and ion beam assisted deposition (IBAD) techniques followed by epitaxial growth to produce the buffer architectures IBAD-YSZ and epi-YSZ/IBAD-YSZ onto optically polished hastelloy metal substrates. Subsequent in situ deposition of YBCO films is used to determine the biaxial alignment at the surface of the buffer architecture, and to show that 100-200 nm thick epi-YSZ layers suffice to yield YBCO tapes that have enhanced biaxial alignment ({delta}phi=9-10 deg. ) and high critical current densities: J{sub c}(77 K)=(1-2)x10{sup 6} A cm{sup -2} and J{sub c}(5 K,1 T)=8x10{sup 6} A cm{sup -2}. Atomic force microscopy of the surface microstructure of the YSZ buffer layers and YBCO films reveals some grain coarsening in the epi-YSZ layers compared to the IBAD-YSZ layers while the YBCO tapes show significant outgrowths ({approx}200 nm) and large grains (800-1200 nm) that are similar to high-J{sub c} YBCO films grown on single crystal MgO(1 0 0) substrates.

Savvides, N.; Gnanarajan, S

2003-05-15

237

Quantum-Classical Phase Transition of Escape rate in Biaxial Spin Particles  

CERN Multimedia

The escape rates of the biaxial single domain spin particles with and without an applied magnetic field are investigated. Using the strict potential field description of spin systems developed by Ulyanov and Zaslavskii we obtain new effective Hamiltonians which are considered to be in exact spin-coordinate correspondence unlike the well studied effective Hamiltonians with the approximate correspondence. The sharp first-order transition is found in both cases. The phase diagram of the transitions depending on the anisotropy constant and the external field is also given.

Zhang, Y B; Müller-Kirsten, H J W; Kou, S P; Wang, X B; Pu, F C

1999-01-01

238

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

International Nuclear Information System (INIS)

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

2002-03-29

239

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

International Nuclear Information System (INIS)

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

2011-01-01

240

NMR properties of 3He-A in biaxially anisotropic aerogel  

Science.gov (United States)

Theoretical model of G.E. Volovik for A-like phase of 3He in aerogel suggests formation of Larkin-Imry-Ma state of Anderson-Brinkmann-Morel order parameter. Most of results of NMR studies of A-like phase are in a good agreement with this model in assumption of uniaxial anisotropy, except for some of experiments in weakly anisotropic aerogel samples. We demonstrate that these results can be described in frames of the same model in assumption of biaxial anisotropy. Parameters of anisotropy in these experiments can be determined from the NMR data.

Dmitriev, V. V.; Krasnikhin, D. A.; Senin, A. A.; Yudin, A. N.

2012-12-01

 
 
 
 
241

Smectic-A-smectic-C phase transition in biaxial disordered environments.  

UK PubMed Central (United Kingdom)

We study the smectic-A-smectic-C phase transition in biaxial disordered environments, e.g., fully anisotropic aerogel. We find that both the A and C phases belong to the universality class of the "XY Bragg glass," and therefore have quasi-long-ranged translational smectic order. The phase transition itself belongs to a new universality class, which we study using an ?=7/2-d expansion. We find a stable fixed point, which implies a continuous transition, the critical exponents of which we calculate.

Chen L; Toner J

2012-03-01

242

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

International Nuclear Information System (INIS)

[en] 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)

1983-01-01

243

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

International Nuclear Information System (INIS)

[en] 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

1975-11-17

244

The Correlation of Stress-State and Nano-Mechanical Properties in Au  

Energy Technology Data Exchange (ETDEWEB)

A dependence of elastic response on the stress-state of a thin film has been demonstrated using the interfacial force microscope (IFM). Indentation response was measured as a function of the applied biaxial stress-state for 100 nm thick Au films. An increase in measured elastic modulus with applied compressive stress, and a decrease with applied tensile stress was observed. Measurements of elastic modulus before and after applying stress were identical indicating that the observed change in response is not due to a permanent change in film properties.

HOUSTON,JACK E.; JARAUSCH,K.F.; KIELY,J.D.; RUSSELL,P.E.

1999-10-07

245

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

Directory of Open Access Journals (Sweden)

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.

Belinda Pingguan-Murphy; Illida Nawi

2012-01-01

246

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

Energy Technology Data Exchange (ETDEWEB)

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.

Chudzik, M. P.

1998-09-17

247

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-01-01

248

Biaxial strain effects on the structure and stability of self-interstitial clusters in silicon  

Science.gov (United States)

Using first-principles density-functional theory calculations, we examine variations in the structure and stability of small self-interstitial clusters (In,n?10) in crystalline silicon across a range of biaxial strain conditions (-3%???3%) on Si(100). Under the strain conditions considered, there is no significant deviation in the ground-state configuration of any cluster from the strain-free case. However, the relative stability of I4 and I8 is significantly increased under both compressive and tensile strain conditions, while other cluster sizes generally show less sensitivity to changes in strain. This suggests that I4 and I8 likely play an even larger role in the clustering/dissolution of interstitial defects in strained Si relative to strain-free Si. We find that the noteworthy strain dependence of I4 and I8 is attributed to the unique shape and symmetry of the I4 -like core which allows reorientation within the lattice that is dependent on the compressive/tensile nature of biaxial strain.

Bondi, Robert J.; Lee, Sangheon; Hwang, Gyeong S.

2009-03-01

249

On the Elastic Energy Density of Constrained Q-Tensor Models for Biaxial Nematics  

Science.gov (United States)

Within the Landau-de Gennes theory, the order parameter describing a biaxial nematic liquid crystal assigns a symmetric traceless 3 × 3 matrix Q with three distinct eigenvalues to every point of the region ? occupied by the system. In the constrained case of matrices Q with constant eigenvalues, the order parameter space is diffeomorphic to the eightfold quotient {{S}^3/{H}} of the 3-sphere {{S}^3}, where {{H}} is the quaternion group, and a configuration of a biaxial nematic liquid crystal is described by a map from ? to {{S}^3/{H}}. We express the (simplest form of the) Landau-de Gennes elastic free-energy density as a density defined on maps {q: ? to {S}^3}, whose functional dependence is restricted by the requirements that (1) it is well defined on the class of configuration maps from ? to {{S}^3/{H}} (residual symmetry) and (2) it is independent of arbitrary superposed rigid rotations (frame indifference). As an application of this representation, we then discuss some properties of the corresponding energy functional, including coercivity, lower semicontinuity and strong density of smooth maps. Other invariance properties are also considered. In the discussion, we take advantage of the identification of {{S}^3} with the Lie group of unit quaternions {Sp(1) \\cong SU(2)} and of the relations between quaternions and rotations in {{R}^3} and {{R}^4}.

Mucci, Domenico; Nicolodi, Lorenzo

2012-12-01

250

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

Science.gov (United States)

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

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

2012-06-01

251

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Objetivo: O objetivo do estudo é avaliar o efeito do modo de ativação na resistência flexual biaxial (RF) e módulo (MF) em cimentos resinosos duais. Metodologia: Foram formados oito grupos experientais (n=12) de acordo com cimento resinos (Nexus 2/Kerr Corp. and Variolink II/IvoclarVivadent), modo ...

Di Francescantonio, Marina et al.

252

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

International Nuclear Information System (INIS)

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

2000-01-01

253

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

International Nuclear Information System (INIS)

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

254

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 a...

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

255

2-D Biaxial Testing and Failure Predictions of IM7/977-2 Carbon/Epoxy Quasi-Isotropic Laminates.  

Science.gov (United States)

In previous research, a series of a thickness-tapered cruciform specimen configurations have been used to determine the biaxial (two- dimensional, in-plane) and triaxial (three-dimensional) strength of several carbon/epoxy and glass/vinyl-ester laminate c...

A. C. Biskner J. S. Mayes J. S. Welsh

2006-01-01

256

Internal stresses and strains in coherent multilayers  

Energy Technology Data Exchange (ETDEWEB)

Formulae are given for the strain and stress tensors in a periodic multilayer which may contain any number of layers, each with a different lattice parameter, different elastic constants and different thickness. The layers are assumed to be parallel sided, elastically isotropic and to have a thickness much smaller than the dimensions in the plane of the layers. The results are applied to metal and semiconductor heterostructures which contain equi-biaxial tensions and compressions and to lamellar Ti-Al in which there are additional in-plane shears. A preliminary discussion is given of the loss of coherency in a multilayer with layers of different thicknesses.

Shoykhet, B. [Wright Lab., Wright-Patterson AFB, OH (United States). Materials Directorate]|[Reliance Electric Co., Cleveland, OH (United States); Grinfeld, M.A. [Wright Lab., Wright-Patterson AFB, OH (United States). Materials Directorate]|[Educational Testing Service, Princeton, NJ (United States); Hazzledine, P.M. [Wright Lab., Wright-Patterson AFB, OH (United States). Materials Directorate]|[UES Inc., Dayton, OH (United States)

1998-07-01

257

High-cycle and long-life fatigue of 25CrMo4 under multiaxial load conditions by three alternating stresses  

International Nuclear Information System (INIS)

Statistically verified experimental results from high-cycle and long-life fatigue tests (HCF and LLF) with altogether 537 unnotched solid cylindrical and thin-walled hollow specimen are demonstrating the fatigue behaviour (S-N-characteritics, scatterband) of 25CrMo4 under uniaxial loading with superimposed static stresses (consideration of the mean stress effect) and under biaxial loadings in variation of phase differences between the three combined normal and torsional stresses ?x, ?y, ?xy. The fatigue strength is commonly decreasing with life time in the high-cycle regime until reaching the fatigue endurance limit in the transition range to infinite life. The 'ductility level' ?W/?W and the 'mean stress sensibility' p=p (?W, ?zSch, Rm) are relatively independent of the intensity by stress amplitudes and fatigue life to failure. In comparison with the specific case of biaxial combined loading with synchroneous amplitudes, the fatigue resistance characteristics are detrimentally influenced by out-of-phase normal stresses ?x, ?y; a phase difference of 180deg between the normal stress amplitudes is the most critical state of combination, especially in the lower cycle regime caused by a greater slope coefficient (probability of survival Ps=50%). On the contrary is there in the high-cycle regime as well as in the long-life range no significant influence to the fatigue strength by biaxial load conditions of simultaneously normal stresses with out-of-phase torsional stress ?xy. (orig.).

1991-01-01

258

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.

1997-01-01

259

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english OBJECTIVES: The promotion of extracellular matrix synthesis by chondrocytes is a requisite part of an effective cartilage tissue engineering strategy. The aim of this in vitro study was to determine the effect of bi-axial cyclic mechanical loading on cell proliferation and the synthesis of glycosaminoglycans by chondrocytes in threedimensional cultures. METHOD: A strain comprising 10% direct compression and 1% compressive shear was applied to bovine chondrocytes seeded in (more) 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

Pingguan-Murphy, Belinda; Nawi, Illida

2012-08-01

260

DIC-aided biaxial fatigue tests of a 304L steel  

Science.gov (United States)

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.

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

2010-06-01

 
 
 
 
261

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.).

1995-01-01

262

Pseudo-dynamic buckling experiment of thin cylindrical shells under biaxial seismic loads  

International Nuclear Information System (INIS)

Pseudo-dynamic budding experiments are performed to study the dynamic buckling characteristics of the main vessel of a fast breeder reactor when subjected to seismic loads. The effects of axial loads on the horizontal seismic responses in pre- and post-buckling states of thin cylindrical shells are investigated. The buckling tests use model cylinders made of 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 region 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. (author)

1993-01-01

263

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

Energy Technology Data Exchange (ETDEWEB)

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.).

Nakagawa, M. [Hitachi Ltd., Ibaraki (Japan). Mech. Eng. Res. Lab.; Fukuyama, M. [Hitachi Ltd., Ibaraki (Japan). Mech. Eng. Res. Lab.; Ishihama, K. [Hitachi Works, Hitachi Ltd., Ibaraki (Japan); Ikeuchi, H. [Hitachi Works, Hitachi Ltd., Ibaraki (Japan); Hagiwara, Y. [Central Research Institute of Electric Power Industry, Tokyo (Japan)

1995-07-01

264

Uniaxial and biaxial mechanical characterization of a prosthetic mesh at different length scales.  

UK PubMed Central (United Kingdom)

This study is aimed at a comprehensive experimental analysis of the mechanical behavior of a prosthetic mesh considering different length scales. Uniaxial and biaxial protocols are developed to evaluate global mechanical phenomena of the dry mesh. Furthermore, procedures for local deformation analysis and evaluation of corresponding homogenized kinematic measures are described. The global mechanical response of the prosthetic mesh is characterized by anisotropy, a nonlinear force response, hysteresis and preconditioning effects. The local deformation analysis allows to identify mesh specific phenomena related to mechanisms at the unit cell level. The global and the local kinematic responses of the mesh are seen to be directly related to clinical observations and help to understand associated complications, such as wrinkle formation, dislocation or erosion. In that sense, this study contributes to the analysis of mechanical biocompatibility of mesh implants and proposes protocols for comprehensive mesh product descriptions.

Röhrnbauer B; Mazza E

2013-08-01

265

EFFECTS OF ELECTRIC FIELD ON THE BIAXIAL STRENGTH OF POLED PZT  

Energy Technology Data Exchange (ETDEWEB)

The mechanical integrity of piezoelectric ceramics plays a crucial role in the performance and design of lead zirconate titanate (PZT) piezo stack actuators especially as PZT actuators become physically larger and are sought to operate under harsher conditions. The reliable design of such systems demands additional consideration of a number of issues that include electro-mechanical coupling as well as strength-size scaling. This study addresses some of those issues through the use of ball-on-ring (BoR) equibiaxial flexure strength tests of two PZT piezo ceramics. The BoR biaxial flexure tests were conducted with two PZT materials under different electric fields. Fracture surfaces and failure initiations were analyzed using optical and scanning electronic microscopy. The effects of electric fields on the two-parameter Weibull distribution are discussed. These results will serve as input data for future probabilistic reliability analysis of multilayer PZT piezo actuators.

Wang, Hong [ORNL; Wereszczak, Andrew A [ORNL

2007-01-01

266

The effect of casting conditions on the biaxial flexural strength of glass-ceramic materials.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To assess the effect of mould and glass casting temperatures on the biaxial flexural strength (BFS) of two different types of castable glass-ceramic, using existing laboratory equipment and techniques. METHODS: Two castable glass-ceramic materials were evaluated. One glass (LG3) is based on SiO2-Al2O3-P2O5-CaO-CaF2, and is similar in composition to glasses used in the manufacture of glass-ionomer cements. The other glass (SG3) is based on SiO2-K2O-Na2O-CaO-CaF2, and is a canasite-based material. Both materials were used to produce discs of 12 mm diameter and 2 mm thickness using the same lost-wax casting process as used for metal castings. Mould temperatures of between 500 degrees C and 1000 degrees C and glass casting temperatures of between 1100 degrees C and 1450 degrees C were evaluated. The cast discs were cerammed and the biaxial flexural strength determined with a Lloyd 2000 R tester. RESULTS: A significant difference was found for the BFS in the range of mould temperatures evaluated, with the optimum investment mould temperature being 590 degrees C for LG3 and 610 degrees C for SG3 (p = 0.0002 and p = 0.019, respectively). No significant differences were seen between any of the glass casting temperatures evaluated. SIGNIFICANCE: The mould temperature for castable glass-ceramic materials produced using the lost-wax casting process can have a significant effect on BFS. The optimum mould temperature may differ slightly depending on the type of material being used. The glass casting temperature of these materials does not appear to have a significant effect on BFS.

Johnson A; Shareef MY; Walsh JM; Hatton PV; van Noort R; Hill RG

1998-11-01

267

In-situ stress determination of Devonian shales. [Depth - 1500 to 8000 ft  

Energy Technology Data Exchange (ETDEWEB)

One of the important design parameters to improve natural gas recovery from Devonian shale through hydraulic fracturing operations is to determine accurate values of in-situ stresses at depths between 1500 and 8000 feet. This study has attempted to develop a methodology to accurately and economically determine the magnitude of overburden pressure and horizontal (in-situ) stresses. This is attempted, herein, through an extensive experimental program to establish basic mechanical properties, and through a refined analytical model based on the finite element method accounting for the stress-relieved core fracture phenomenon. In compliance with the ASTM and Bureau of Mines standards, Devonian shale samples were tested under split tension, direct tension, three-point bending, uniaxial and biaxial compression and direct shear to find the mechanical properties, fracture toughness and stress-strain behavior in the overburden and bedding plane directions. The proposed analytical phase to find horizontal stresses by incorporating the mechanical properties and fracture toughness constants has not been carried out due to difficulties encountered in implementing the computer based model on WVNET for Educational Telecomputing. However, the stress memory concept has been utilized to determine the overburden and horizontal stresses through the stress-strain plots of Devonian shales under biaxial compression. It has been shown that the overburden and horizontal stresses from the stress-strain plots compared extremely well (+- 5 percent) with the stresses obtained from the field hydraulic fracturing experiments. Based on the experience gained during this research program, pertinent recommendations are made.

Gangarao, H.V.S.

1981-06-01

268

Variations of biaxial orientation of polyester film on laminated steel in the laminating process; Kohan eno laminate ni tomonau nijiku haiko polyester film no haiko henka  

Energy Technology Data Exchange (ETDEWEB)

Polyester film laminated steel for can container will gradually replace lacquer coated steel sheet from environmental consideration and cost reduction. The process is characterized by partial melting of the film on the steel surface during lamination by pressing the supplied films between both sides of heated steel and a couple of cooled rubber rolls. At present, most of polyester films used for the can containers are biaxially oriented films and various characteristics of film laminated steel for can use are strongly influenced by the degree of biaxial orientation of the laminated film. Therefore, this report deals with the result of an experiment regarding variations of the degree of biaxial orientation with several polyester films, and thermal analysis of these polyester films by means of Differential Scanning Calorimeter (DSC). Finally, from these experiments, we found that it is possible to estimate the variation of the degree of biaxial orientation during lamination by means of thermal analysis. (author)

Morita, S.; Iwashita, H.; Tanaka, A.; Terauchi, F. [Toyo Kohan Co. Ltd., Tokyo (Japan)

2000-03-01

269

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.

2005-02-01

270

Quantitative biaxial texture analysis with reflection high-energy electron diffraction for ion beam-assisted deposition of MgO and heteroepitaxy of perovskite ferroelectrics  

Science.gov (United States)

To facilitate ferroelectric-based actuator integration with silicon electronics fabrication technology, we have developed a route to produce biaxially textured ferroelectrics on amorphous layers by using biaxially textured MgO templates. Using a kinematical electron scattering model, we show that the RHEED pattern from a biaxially textured polycrystalline film can be calculated from an analytic solution to the electron scattering probability. We found that diffraction spot shapes are sensitive to out-of-plane orientation distributions and in-plane RHEED rocking curves are sensitive to the in-plane orientation distribution. Using information from the simulation, a RHEED-based experimental technique was developed for in situ measurement of MgO biaxial texture. The accuracy of this technique was confirmed by comparing RHEED measurements of in-plane and out-of-plane orientation distribution with synchrotron x-ray rocking curve measurements. Biaxially textured MgO was grown on amorphous Si3N4 by ion beam-assisted deposition (IBAD). MgO was e-beam evaporated onto the amorphous substrate with a simultaneous 750--1200 eV Ar+ ion bombardment at 45° from normal incidence. We observed a previously unseen, dramatic texture evolution in IBAD MgO using transmission electron microscopy (TEM) and RHEED-based quantitative texture measurements of MgO. The first layers of IBAD MgO are diffraction amorphous until the film is about 3.5 nm thick. During the next 1 nm of additional growth, we observed rapid biaxial texture evolution. RHEED and TEM studies indicate that biaxially textured MgO film results from a solid phase crystallization of biaxially textured MgO crystals in an amorphous matrix. Biaxially textured perovskite ferroelectrics were grown on biaxially textured MgO templates using sol-gel, metallorganic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE). Through RHEED-based biaxial texture analysis we observed that the heteroepitaxial ferroelectric in-plane orientation distribution, deposited using ex situ techniques (not performed in the same high vacuum growth environment where the MgO was deposited), narrowed significantly with respect to the in-plane orientation distribution of its MgO template (from 11° to 6° FWHM). Evidence from cross section TEM and RHEED suggest that atmospheric moisture degrades the crystallinity of highly defective, misaligned MgO grains and that heteroepitaxially grown ferroelectrics preferentially nucleate on well-aligned grains and over grow misaligned regions of MgO.

Brewer, Rhett Ty

271

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.

2005-12-22

272

High-rate reel-to-reel continuous coating of biaxially textured magnesium oxide thin films for coated conductors  

Energy Technology Data Exchange (ETDEWEB)

Biaxially textured thin films of magnesium oxide (MgO) were deposited by electron beam evaporation at deposition rates of 0.6 {mu}m/min on moving Ni-based alloy tapes as oriented buffer layers for coated conductors. Moving substrates were inclined with respect to the atomic vapor and translated through collimated dual vapor sources. Growth anisotropy in the MgO and self-shadowing effects due to the inclined angle combine to create biaxial texture in the deposited thin films. MgO films grown to a thickness of 2.0 {mu}m with this inclined-substrate deposition technique have yielded in-plane textures of 10--12{degree} fill-width half-maximum (FWHM). Results of a parametric study on the in-plane texture in short-length static-mode samples are presented, along with preliminary results of long-length samples deposited under translating conditions.

Chudzik, M. P.; Erck, R. A.; Balachandran, U.; Luo, Z. P.; Miller, D. J.; Kannewurf, C. R.

2000-01-12

273

Biaxially-Textured Photovoltaic Film Crystal Silicon on Ion Beam Assisted Deposition CaF2 Seed Layers on Glass  

Energy Technology Data Exchange (ETDEWEB)

We grow biaxially textured heteroepitaxial crystal silicon (c-Si) films on display glass as a low-cost photovoltaic material. We first fabricate textured CaF{sub 2} seed layers using ion-beam assisted deposition, then coat the CaF{sub 2} with a thin, evaporated epitaxial Ge buffer and finally deposit heteroepitaxial silicon on the Ge. The silicon is grown by hot-wire chemical vapor deposition, a high-rate, scalable epitaxy technology. Electron and X-ray diffraction confirm the biaxial texture of the CaF{sub 2} and epitaxial growth of the subsequent layers. Transmission electron microscopy reveals columnar silicon grains about 500 nm across. We fabricate a proof-of-concept epitaxial film c-Si solar cell with an open circuit voltage of 375 mV that is limited by minority carrier lifetime.

Groves, J. R.; Li, J. B.; Clemens, B. M.; LaSalvia, V.; Hasoon, F.; Branz, H. M.; Teplin, C. W.

2012-05-01

274

Development and evolution of biaxial texture of rolled nickel tapes by ion beam bombardment for high Tc coated conductors  

International Nuclear Information System (INIS)

High quality YBa2Cu3O7-x films on metallic substrates with high critical current densities well over 106 A/cm2 can be prepared by the rolling assisted biaxially textured substrates (RABiTS) method. Nickel or its alloys have been used as biaxially textured substrates formed through a specific rolling and high temperature annealing procedures. In this paper, we report a newly developed process for developing biaxial texture in rolled Ni tape by argon ion beam bombardment. It is named the ion-beam structure modification (ISM) process. In the ISM processed Ni foils, X-ray diffraction ? scans showed the full width-half maximum (FWHM) value of the (2 0 0) peak was 5.7 deg. . And the electron back scattering diffraction (EBSP) analysis based on scanning electron microscopy showed good {1 0 0} cubic orientation and the mean grain size was determined as about 25 ?m. The texture evolution of rolled Ni foils during ISM process is reported also. For ISM process, local temperature elevation and distribution arises from the ion bombardment, coupled with anisotropic incident ion penetration and propagation as a result of channeling effects in the metal lattice, are expected to play the major roles in the development of grain reorientation in the Ni foil. Due to the simplicity and efficiency of the ISM process, the technique shows a great promise for application in the industrial scale production of long-lengths of superconductor tapes

2004-08-15

275

Observations of grain-boundary sliding and surface topography in an 8090 Al alloy after uniaxial and biaxial superplastic deformation  

Energy Technology Data Exchange (ETDEWEB)

The surface topography of an 8090 aluminum alloy was studied after uniaxial or biaxial superplastic deformation, with particular reference to grain-boundary sliding (GBS) offsets, grain rotation angles, formation of striated bands (SBs) or fibers, cavity distribution, and cavity formation mechanisms. Additionally, the contribution of GBS or grain separation to the overall strain was evaluated. Striated bands were observed and are thought to be the newly exposed faces of the grains inclined to the specimen`s surface. They were formed by sliding of grains upward and downward relative to the specimen surface. Grooves and crests inside SBs were formed from the relative motion of grain-boundary defects. Fibers were observed and are thought to be the further development of the SBs resulting from the formation of elongated cavities and grain separation. More cavitation was found in equibiaxially strained regions than in other regions subjected to approximately equivalent levels of strain. About 50 pct of the total strain was contributed to GBS in the uniaxial tensile-loaded specimens, as compared to about 30 pct in the biaxial-strained specimens. The effects of grain separation, grain rotation, and secondary GBS may be the reasons for the reduction of the observed strain contribution from GBS in biaxially strained specimens.

Chen, T.R.; Huang, J.C. [National Sun Yat-Sen Univ., Kaohsiung (Taiwan, Province of China). Inst. of Materials Science and Engineering

1999-01-01

276

A PHYSICS BASED MODEL OF INVERSION CHARGE SHEET (ICS) FOR NANOSCALE BIAXIAL STRAINED – SILICON NMOSFET INCLUDING QUANTUM MECHANICAL EFFECT (QME)  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a physics based model of inversion charge sheet of nanoscale NMOSFETs has been presented. The model is formulated for nanoscale biaxial strained silicon NMOSFET including quantum mechanical effect (QME). The QME is splitting of conduction band due to very thin oxide (tox) and very large doping concentration of ultra small geometry of MOSFET. The QME shift the inversion charge sheet into subtracts. To overcome this problem strain technique is used because this shift is very small but this is effect causes increase in the surface potential as well as threshold voltage of nanoscale MOSFET. The modeling approach is to develop the model for inversion charge sheet after combining both QME and strain effect for biaxial strained silicon NMOSFET .The result shows a significant decrease in the inversion charge sheet of increasing the germanium mole fraction (%x) in silicon germanium heterostrusture virtual substrate. The presented result has been good agreement with published data. The result shows that QME is minimized by using strain technique in biaxial strained silicon NMOSFET. Presented result is valid for large range of doping concentration as well as mole fraction.

Shiromani Balmukund Rahi; Garima Joshi

2013-01-01

277

Stress measurements in the Naesliden Mine  

Energy Technology Data Exchange (ETDEWEB)

Determinations of virgin stresses were performed at an early stage of the Naesliden Project in order to obtain input data for the finite element models of the mine. The Leeman three-dimensional overcoring technique was used at five locations on levels ranging from 210 m to 460 m below surface. Stress data were obtained at four of these locations. The results show an excess of horizontal stresses whilst the vertical stress is in accordance with the gravitational load from the overburden. The major and intermediate principal stresses are sub-horizontal and directed respectively perpendicular and parallel to the schisotsity of the wall rock and the strike of the tabular ore body. The minor principal stress is directed almost vertically. Stresses were also measured close to a stope on 300 m level in the mine. Biaxial and triaxial overcoring measurements were made at eighteen points between 0.25 m and 7.2 m above the roof of the stope. The stresses were found to have magnitudes of about 70 MPa close to the roof and to decrease rapidly with the distance from the roof. Stress measurements were made in connection with slot blastings in the foot wall, the latter measure being made in an attempt to de-stress the roof of stope 3. Two methods were used for stress monitorings, both showing that expected stress changes did not take place. Long-term stress guages have been installed in the ore body in order to monitor expected re-distributions of stresses due to mining. So far, the recorded stress changes are below 5 MPa.

Leijon, B. (Univ. of Luleaa, Sweden); Carlsson, H.; Myrvang, A.

1980-05-01

278

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

Science.gov (United States)

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

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

2003-08-11

279

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

UK PubMed Central (United Kingdom)

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

Panov VP; Vij JK; Shtykov NM; Seomun SS; Parghi DD; Hird M; Goodby JW

2003-08-01

280

Managing Stress  

Science.gov (United States)

... tips for managing and preventing stress. What Is Stress? Many scientists see stress as a reaction of ... called “bad stress” or “chronic stress.” Risks of Stress Never-ending stress can lead to a variety ...

 
 
 
 
281

Managing Stress  

Medline Plus

Full Text Available ... tips for managing and preventing stress. What Is Stress? Many scientists see stress as a reaction of ... called “bad stress” or “chronic stress.” Risks of Stress Never-ending stress can lead to a variety ...

282

Integration of Low-? Dielectric Liner in Through Silicon Via and Thermomechanical Stress Relief  

Science.gov (United States)

Through silicon via (TSV) consists of a copper (Cu) core isolated by a dielectric liner. The thermomechanical stress originating from the mismatch in the coefficient of thermal expansion of Cu and silicon is a serious concern on mechanical reliability and electrical variability. The effect on thermomechanical stress by replacing the conventional liner (silicon dioxide) with a low-? liner (carbon-doped silicon dioxide) is studied. By micro-Raman analysis, it is observed that the biaxial stress in silicon at the immediate vicinity of Cu-TSV is relieved by 29--45% with a low-? liner due to its smaller elastic modulus.

Ghosh, Kaushik; Zhang, Jiye; Zhang, Lin; Dong, Yuanwei; Li, Hongyu; Tan, Cher Ming; Xia, Guangrui; Tan, Chuan Seng

2012-12-01

283

Electronic structure and optical properties of CuAlO2 under biaxial strain.  

UK PubMed Central (United Kingdom)

An ab initio calculation has been carried out to investigate the biaxial strain ( - 10.71% < ? < 9.13%) effect on elastic, electronic and optical properties of CuAlO(2). All the elastic constants (c(11), c(12), c(13), c(33)) except c(44) 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 CuAlO(2).

Ghosh CK; Sarkar D; Mitra MK; Chattopadhyay KK

2012-06-01

284

Analysis of biaxial strain in InN(0001) epilayers grown by molecular beam epitaxy  

International Nuclear Information System (INIS)

The in-plane lattice parameters of InN, GaN and Al2O3 in a InN/GaN/Al2O3(0001) heterostructure have been measured as a function of temperature in the range of 25-350 C, using high resolution X-ray diffraction. The results reveal that both the GaN and InN crystals follow the in-plane thermal expansion of the Al2O3 substrate's lattice and there is no rearrangement of misfit dislocations at the InN/GaN and GaN/Al2O3 interfaces. It was also found that either compressive or tensile character of residual biaxial strain is possible for the InN films, depending on the two-dimensional (2D) or three-dimensional (3D) growth mode of InN on the GaN(0001) buffer layer. The tensile strain is inherent to the nucleation and coalescence of 3D islands. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

2007-01-01

285

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

International Nuclear Information System (INIS)

Biaxially textured tungsten nanorods (A15 crystal structure) have been grown by oblique angle DC magnetron sputtering using a novel rotation mode called 'two-step rotation'. In this mode, the substrate is given a fast rotation through 1800 at 90 rpm and this is followed by a rest period of 30 s. These nanorods are vertically aligned and have a [100] texture normal to the substrate along with preferential in-plane texture as shown by x-ray pole figure analysis. In contrast, the tungsten nanorods obtained without substrate rotation are slanted at an angle of ?450 and have a [100] texture tilted 160 with respect to the substrate normal. The flux is incident from two diametrically opposite points on the sample at an oblique angle, averaging out the growth into vertical columns that retain the in-plane texture. Scanning electron microscopy shows that the tungsten nanorods have a mixture of {211} and {421} crystal habits; these planes are both minimum surface energy planes for a cubic A15 crystal structure.

2009-11-18

286

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)

2011-01-01

287

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english This article investigates a fatigue approach conducted from the design phase to testing approval. It considerers modern analytical and experimental tools for structural durability assessment over each development phase for two reference components aiming an early approval methodology validation for a new design. A Finite element analysis procedure was used to set critical spots for measurements minimizing the data acquisition efforts. Based on measured data, strain life c (more) alculation 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.

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

2013-01-01

288

Biaxially textured Mo films with diverse morphologies by substrate-flipping rotation  

International Nuclear Information System (INIS)

A class of nanostructured Mo thin films was grown by DC magnetron sputtering using a robust substrate rotation mode called 'flipping rotation'. 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 perpendicular to the rotational axis, and the incident flux angle changes continuously. Mo nanostructured films, grown under different rotation speeds with three orders of magnitude spread (ranging from 0.008 to 24 rotation min?1), different flipping directions (clockwise and counter-clockwise), and different ending deposition angles, were characterized using scanning electron microscopy (SEM) and reflection high energy electron diffraction (RHEED) surface-pole-figure techniques. Despite their very different morphologies, such as 'C'-shaped, 'S'-shaped, and vertically aligned nanorods, the same (110)[1 1-bar 0] biaxial texture with an average out-of-plane dispersion of ? 15° was observed. In contrast, we showed that only a fiber-textured Mo film was obtained by using the conventional rotation mode where the oblique incident flux angle was fixed with the substrate rotating around the surface normal.

2011-12-16

289

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

Directory of Open Access Journals (Sweden)

Full Text Available Nowadays titanium and titanium alloys are increasingly being used in the industry. Particularly ?-Ti alloys that stand out for having great strength properties and low elastic modulus compared to Ti c.p. or Ti-6Al-4V. Among Ti alloys, Ti-Nb alloys with high contents of alloying elements are widely used. In this work Ti-Nb alloys have been obtained using conventional powdermetallurgy. It has been studied the evolution of properties of these alloys as a function of the percentage of niobium. It can be noted the ball on three balls test used in order to characterize the samples.En la actualidad, cada vez, son más importantes en la industria las aleaciones de titanio. En especial las aleaciones tipo-?, que destacan por tener buenas propiedades resistentes y bajos módulos elásticos, en comparación con el Ti c.p. o el Ti-6Al-4V. Dentro de estas aleaciones cabe destacar las Ti-Nb con altos contenidos en elementos aleantes. En este trabajo se han obtenido, mediante pulvimetalurgia convencional, una serie de aleaciones Ti-Nb, en el rango del 20-40 % de niobio. Se ha obtenido la evolución de las propiedades de dichas aleaciones en función del porcentaje de niobio, mediante la utilización del ensayo de flexión biaxial con tres apoyos (three ball test).

Benavente-Martínez, E.; Devesa, F.; Amigó, V.

2010-01-01

290

Fabrication of biaxially textured magnesium oxide thin films by ion-beam-assisted deposition  

International Nuclear Information System (INIS)

Biaxially textured MgO thin films were grown by ion-beam-assisted deposition. The film growth parameters of film thickness, ion-to-atom arrival ratio (r-value), ion beam angle, and ion beam voltage were studied. Film characterization was performed by X-ray diffraction, pole figure analysis, and atomic force microscopy (AFM). Full-width half-maximum (FWHM) of MgO (220) ?-scans and MgO (002) ?-scans, respectively, were used to evaluate in-plane and out-of-plane film texture. MgO (220) ?-scan FWHM of 3.2 deg and MgO (002) ?-scan FWHM of 1.2 deg was achieved on amorphous Si3N4-coated Si substrates using a 1500-V ion source oriented at 45 deg to the substrate normal and an r-value of 0.90. Depositions on metallic substrates yielded MgO (220) ?-scan FWHM values of 5.2 deg and MgO (002) ?-scan FWHM of 2.5 deg . Root-mean-square surface roughness of these films as measured by AFM was ?2.3 nm.

2005-04-01

291

Buffer layers on metal surfaces having biaxial texture as superconductor substrates  

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-01-01

292

Dispersion equations for vacuum-deposited tilted-columnar biaxial media.  

Science.gov (United States)

We consider the application of the Bragg-Pippard (BP) equations for form birefringence to a tilted-columnar biaxial thin film with columns of index n(c) and voids of known index n(v). In such a situation the three forward BP equations that express the principal refractive indices n1, n2, and n3 as functions of n(c), n(v), the packing fraction p(c), and the depolarization factors L1, L2, and L3 can be inverted. The procedure described for adding dispersion to the principal indices involves entry to the BP model via the inverted equations, modification of n(c) to allow for dispersion, and then exit from the model via the forward BP equations. We discuss the introduction of composite columns to the model to allow for angular dependence of n(c) and the selection of suitable dispersion functions for bulk tantalum oxide, titanium oxide, and zirconium oxide. Theory and experiment both show that the dispersion of the normal-incidence birefringence Deltan of the thin films is several times larger than the dispersion of the individual principal refractive indices. PMID:18357018

Hodgkinson, I; Wu, Q H; Collett, S

2001-02-01

293

Dispersion equations for vacuum-deposited tilted-columnar biaxial media.  

UK PubMed Central (United Kingdom)

We consider the application of the Bragg-Pippard (BP) equations for form birefringence to a tilted-columnar biaxial thin film with columns of index n(c) and voids of known index n(v). In such a situation the three forward BP equations that express the principal refractive indices n1, n2, and n3 as functions of n(c), n(v), the packing fraction p(c), and the depolarization factors L1, L2, and L3 can be inverted. The procedure described for adding dispersion to the principal indices involves entry to the BP model via the inverted equations, modification of n(c) to allow for dispersion, and then exit from the model via the forward BP equations. We discuss the introduction of composite columns to the model to allow for angular dependence of n(c) and the selection of suitable dispersion functions for bulk tantalum oxide, titanium oxide, and zirconium oxide. Theory and experiment both show that the dispersion of the normal-incidence birefringence Deltan of the thin films is several times larger than the dispersion of the individual principal refractive indices.

Hodgkinson I; Wu QH; Collett S

2001-02-01

294

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

UK PubMed Central (United Kingdom)

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

Freytes DO; Stoner RM; Badylak SF

2008-02-01

295

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

Science.gov (United States)

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

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

2008-02-01

296

Plasma Surface Functionalization of Biaxially Oriented Polypropylene Films with Trimethyl Borate  

Directory of Open Access Journals (Sweden)

Full Text Available The radiofrequency plasma (13.56 MHz) was employed to polymerize trimethyl borate (TMB) monomer/N2 gas mixture on the surface of biaxially oriented polypropylene (BOPP) films. Plasma polymer coated polypropylene films were examined by flame retardancy test (limiting oxygen index, LOI). The highest LOI value calculated for the untreated BOPP sample was 18.4 (v/v O2%) and 24.2 (v/v O2%) for the 55 W 30 minutes treated sample. The plasma polymers were characterized by FTIR spectroscopy and AFM. According to the FTIR results, the -OH, B-CH3, B-O, and BH2 functional groups were detected. It was found that the highest surface roughness belonged to 40 W 30 min treated BOPP sample which was calculated as 9.78 nm (10 ?m × 10 ?m). Moreover, the wettability of the modified BOPP film surfaces was characterized via contact angle measurements. The water contact angle values have decreased from 109.6? to the lowest value of 68.2? after the plasma treatment. The results showed that TMB/N2 plasma modification could be used as an alternative method for the enhancement of flame retardancy and hydrophilicity of BOPP film.

Nursel Dilsiz; Hande Yavuz; Süleyman Çörekçi; Mehmet Çakmak

2011-01-01

297

Altered mechanical behavior of epicardium due to isothermal heating under biaxial isotonic loads.  

UK PubMed Central (United Kingdom)

Recent isothermal biaxial isotonic tests suggest that increasing the temperature hastens the rate of denaturation of epicardium whereas increasing the mechanical load during heating delays this process, findings that are consistent with prior uniaxial tests on tendons. Yet, contrary to uniaxial reports, a clear time-temperature-load equivalency was not found in this multiaxial setting. There is, therefore, a need to delineate multiaxial thermomechanical behavior in greater detail, and ultimately, to correlate changes therein with the underlying microstructure. Toward this end, we describe a new experimental approach for quantifying heating-induced changes in the multiaxial mechanical response of thin sheet-like specimens. Illustrative results are presented for bovine epicardium subjected to nine different thermomechanical loading protocols. Among other results, it is shown that thermal damage tends to increase the stiffness at low strains and that overall changes in extensibility correlate well with the degree of thermal damage independent of the specific thermomechanical protocol. Multiaxial changes in behavior are nevertheless complex, and there is a need for significantly more testing before constitutive relations can be formulated.

Harris JL; Wells PB; Humphrey JD

2003-06-01

298

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

Directory of Open Access Journals (Sweden)

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

Neha Sharan; Ashwani K.Rana

2011-01-01

299

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

Science.gov (United States)

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

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

2012-11-10

300

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

UK PubMed Central (United Kingdom)

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.

Gu CH; Wang JJ; Yu Y; Sun H; Shuai N; Wei B

2013-02-01

 
 
 
 
301

Strengthened, biaxially textured Ni substrate with small alloying additions for coated conductor applications  

International Nuclear Information System (INIS)

Fabrication of a biaxially textured, strengthened Ni substrate with small alloying additions of W and Fe is reported. The substrates have significantly improved mechanical properties compared to 99.99% Ni and surface characteristics which are similar to that of 99.99% Ni substrates. High quality oxide buffer layers can be deposited on these substrates without the need for any additional surface modification steps. Grain boundary misorientation distributions obtained from the substrate show a predominant fraction of low-angle grain boundaries. A high critical current density, Jc, of 1.9 MA/cm2 at 77 K, self-field is demonstrated on this substrate using a multilayer configuration of YBCO/CeO2/YSZ/Y2O3/ Ni-3at.%W-1.7at.%Fe. This translates to a Ic/width of 59 A/cm at 77 K and self-field. Jc at 0.5 T is reduced by only 21% indicating strongly-linked grain boundaries in the YBCO film on this substrate.

2002-11-01

302

Stress field induced by swift heavy ion irradiation in cubic yttria stabilized zirconia  

International Nuclear Information System (INIS)

X-ray diffraction (XRD) was used to investigate the damage and the correlated stress induced by the slowing down of swift heavy ions in cubic zirconia polycrystals doped with 10 mol % Y2O3. Samples were irradiated at room temperature with 940 MeV Pb ions at fluences ranging from 5x1011 to 4x1013 cm-2. Changes of XRD profiles were examined at increasing fluences. Residual macroscopic stresses induced by irradiation were determined using XRD by the ''sin2 ? method.'' The state of stress in the irradiated layer was described by a combination of: (i) a hydrostatic stress caused by the formation of damaged tracks leading to swelling and (ii) a biaxial stress imposed by the bulk undamaged material, which controls the lateral expansion of the surface damaged layer. The evolution of the stress as a function of irradiation fluence was also determined: the intensity of the hydrostatic stress increases from 80 to 460 MPa when the fluence is increased from 5x1011 to 4x1013 cm-2 and that of the biaxial stress increases correlatively from -80 to -1630 MPa

2007-05-15

303

Correlation of acoustic emission generated during uniform biaxial loading to microstructural sources in 7075-T651 aluminum and 21Cr-6Ni-9Mn stainless steel. Final report  

Energy Technology Data Exchange (ETDEWEB)

This paper reports on the effect on acoustic emission (AE) of uniform biaxial loading of a thin-walled tube designed by Hamstad, Patterson and Mukherjee. The AE generated during biaxial loading of 7075-T651 aluminum and 21Cr-6Ni-9Mn stainless steel had several anomalous features relative to tensile generated AE. The biaxial AE data was of a much higher level and peaked at a lower strain than the uniaxial AE response. A particle cracking model was proposed in which inclusions with the largest projected surface area perpendicular to the principal axis of applied loading will crack before smaller inclusions, and the resulting energy released per AE will be proportional to the crack surface area. The inclusion contents were studied with respect to size, shape, density, hardness, and fracture/decohesion behavior. The inclusions in both 7075-T651 and 21-6-9 display the preferred cracking orientation predicted in the Hamstad, et al. model and are shown to be associated with the generated AE. However, other factors appear to contribute to the total AE responses. There is evidence that for 7075-T651 subjected to biaxial loading, a grain boundary-related mechanism becomes a significant source of AE in the latter stages of strain hardening. Also, for both materials, the complex applied load during biaxial loading appears to amplify the level of AE.

Leon, E.; Mukherjee, A.K.

1981-12-01

304

Failure responses of a dental porcelain having three surface treatments under three stressing conditions.  

UK PubMed Central (United Kingdom)

OBJECTIVES: Surface conditions are of interest in all-ceramic restorations since they can control both bonding and strength. Tensile testing methods are commonly used to evaluate surface conditions of ceramics. This work evaluated tensile properties of a feldspathic ceramic as-finished, sandblasted and etched under three stressing conditions: (1) biaxial flexure; (2) monotonic mastication loading, dry; and, (3) cyclic mastication loading, wet. MATERIALS AND METHODS: Feldspathic CAD/CAM blocks were sliced into Tabs 1mm thick, n=135 specimens were divided into 3 groups assigned to as-finished (600 grit SiC; control), sandblasted, and etched. Of the 45 specimens per group, 35 specimens were used for bonded tests and 10 specimens for biaxial flexure testing. Pin-on-three ball biaxial testing was performed per ISO 6872. 35 specimens were bonded to dentin-analog bases and loaded to radial crack pop-in beneath a 3mm diameter piston. 20 specimens were tested dry with failure determined by acoustic emission methods. 15 specimens, bonded to bases having micro-channels for water transport, were cyclically loaded beneath the 3mm piston under water at 15Hz for 500,000 cycles. RESULTS: Biaxial flexure distinguished among all three surface conditions (p<0.05, ANOVA). Monotonic testing could not distinguish among groups. Cyclic testing could not distinguish between sandblasted and etched groups but both were weaker than as-finished. CONCLUSIONS: Mastication loading of bonded specimens creates a different stress state than simple flexure due to contributions of the cement-ceramic interface. Water adds a damage accumulation effect. Tensile stress conditions need to be chosen with the desired outcomes considered.

Yi YJ; Kelly JR

2011-12-01

305

Reduction of initial stress stiffening by topology optimization  

DEFF Research Database (Denmark)

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

Philippine, M. A.; Sigmund, Ole

2012-01-01

306

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

2011-07-01

307

Biaxially textured Al film growth on CaF2 nanostructures toward a method of preparing single-crystalline Si film on glass substrates.  

UK PubMed Central (United Kingdom)

We report the room temperature growth of biaxially textured Al films and further demonstrate the use of these Al films in preparing single-crystalline Si layers on glass substrates. The formation of the biaxial texture in Al film relies on the existence of the CaF(2) buffer layer prepared using oblique angle physical vapor deposition, which consists of single-crystalline nanorods with caps that are in the form of inverted nanopyramids. The single-crystalline Si film was obtained upon crystallization of the amorphous Si film deposited through physical evaporation on the biaxially textured Al film. This method of preparing single-crystalline Si film on glass substrate is potentially attractive for being employed in silicon technology and in fabrication of low-cost electronic devices.

Li H; Snow P; He M; Wang PI; Wang GC; Lu TM

2010-10-01

308

Biaxially textured Al film growth on CaF2 nanostructures toward a method of preparing single-crystalline Si film on glass substrates.  

Science.gov (United States)

We report the room temperature growth of biaxially textured Al films and further demonstrate the use of these Al films in preparing single-crystalline Si layers on glass substrates. The formation of the biaxial texture in Al film relies on the existence of the CaF(2) buffer layer prepared using oblique angle physical vapor deposition, which consists of single-crystalline nanorods with caps that are in the form of inverted nanopyramids. The single-crystalline Si film was obtained upon crystallization of the amorphous Si film deposited through physical evaporation on the biaxially textured Al film. This method of preparing single-crystalline Si film on glass substrate is potentially attractive for being employed in silicon technology and in fabrication of low-cost electronic devices. PMID:20839785

Li, Huafang; Snow, Patrick; He, Ming; Wang, Pei-I; Wang, Gwo-Ching; Lu, Toh-Ming

2010-10-26

309

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-07-01

310

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

International Nuclear Information System (INIS)

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

1998-01-01

311

Controlled clinical trial comparing biaxial microincision with coaxial small incision for cataract surgery.  

UK PubMed Central (United Kingdom)

PURPOSE: Clinical outcomes of biaxial microincision versus coaxial small incision cataract surgery were compared in a prospective, controlled, paired-eye clinical study. METHODS: A total of 84 eyes of 42 patients underwent cataract surgery using the biaxial microincision (B-MICS) technique in either the right or left eye. The fellow eye was to undergo cataract surgery using the standard coaxial small incision (SICS) technique. All surgeries were performed using the Stellaris Vision Enhancement System and all eyes were implanted with an aspheric microincision intraocular lens (IOL). The 1.2-mm B-MICS incision was widened to 1.8 mm for IOL insertion. The main outcome measure was the change from baseline best-corrected visual acuity (BCVA). Secondary outcome measures were uncorrected visual acuity (UCVA), surgically induced astigmatism (SIA), manifest subjective refraction in spherical equivalent (MRSE), absolute phacoemulsification time (APT), effective phacoemulsification time (EPT), mean phacoemulsification power, and endothelial cell count (ECC). Follow-up was at 1 day, 3 days, 1 week, and 2 months. RESULTS: The treatment groups did not differ in baseline characteristics. Improvement in BCVA over baseline logarithm of the minimum angle of resolution (logMAR) was statistically significantly greater with B-MICS than SICS at 1 day (B-MICS -0.1, SICS -0.05; 95% CI -0.26 to -0.05, p=0.005). Mean improvement in UCVA from baseline was greater with B-MICS at 1 day (B-MICS -0.33, SICS -0.12; 95% CI -0.35 to -0.10, p=0.001), 3 days (B-MICS -0.39, SICS -0.26; 95% CI -0.22 to -0.02, p=0.022), 1 week (B-MICS -0.44, SICS -0.33; 95% CI -0.20 to -0.009, p=0.033), and 2 months (B-MICS -0.47, SICS 0.38; 95% CI -0.19 to +0.002, p =0.054). At 2 months, SIA was significantly lower with B-MICS than SICS (B-MICS 0.70 D, SICS 0.89 D; 95% CI -0.39 to -0.1, p=0.045), as was endothelial cell loss (B-MICS -1.4%, SICS -7.8%; p=0.05). The EPT was lower with B-MICS (B-MICS 1.60 s, SICS 2.80 s; 95% CI -1.68 to -0.77, p<0.001) with no difference in mean phaco power. CONCLUSIONS: Compared to the standard small incision technique, B-MICS showed earlier improvement in BCVA, better overall UCVA, less SIA, and less endothelial cell loss.

Dick HB

2012-09-01

312

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

UK PubMed Central (United Kingdom)

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 (p<0.0001) and VHN results were AL, DD>ML (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.

Gordan VV; Patel SB; Barrett AA; Shen C

2003-09-01

313

Collagen fiber alignment and biaxial mechanical behavior of porcine urinary bladder derived extracellular matrix.  

Science.gov (United States)

The collagen fiber alignment and biomechanical behavior of naturally occurring extracellular matrix (ECM) scaffolds are important considerations for the design of medical devices from these materials. Both should be considered in order to produce a device to meet tissue specific mechanical requirements (e.g., tendon vs. urinary bladder), and could ultimately affect the remodeling response in vivo. The present study evaluated the collagen fiber alignment and biaxial mechanical behavior of ECM scaffold material harvested from porcine urinary bladder tunica mucosa and basement membrane (together referred to as urinary bladder matrix (UBM)) and ECM harvested from urinary bladder submucosa (UBS). Since the preparation of UBM allows for control of the direction of delamination, the effect of the delamination method on the mechanical behavior of UBM was determined by delaminating the submucosa and other abluminal layers by scraping along the longitudinal axis of the bladder (apex to neck) (UBML) or along the circumferential direction (UBMC). The processing of UBS does not allow for similar directional control. UBML and UBS had similar collagen fiber distributions, with a preferred collagen fiber alignment along the longitudinal direction. UBMC showed a more homogenous collagen fiber orientation. All samples showed a stiffer mechanical behavior in the longitudinal direction. Despite similar collagen fiber distributions, UBML and UBS showed quite different mechanical behavior for the applied loading patterns with UBS showing a much more pronounced toe region. The mechanical behavior for UBMC in both directions was similar to the mechanical behavior of UBML. There are distinct differences in the mechanical behavior of different layers of ECM from the porcine urinary bladder, and the processing methods can substantially alter the mechanical behavior observed. PMID:18801572

Gilbert, Thomas W; Wognum, Silvia; Joyce, Erinn M; Freytes, Donald O; Sacks, Michael S; Badylak, Stephen F

2008-09-17

314

Collagen fiber alignment and biaxial mechanical behavior of porcine urinary bladder derived extracellular matrix.  

UK PubMed Central (United Kingdom)

The collagen fiber alignment and biomechanical behavior of naturally occurring extracellular matrix (ECM) scaffolds are important considerations for the design of medical devices from these materials. Both should be considered in order to produce a device to meet tissue specific mechanical requirements (e.g., tendon vs. urinary bladder), and could ultimately affect the remodeling response in vivo. The present study evaluated the collagen fiber alignment and biaxial mechanical behavior of ECM scaffold material harvested from porcine urinary bladder tunica mucosa and basement membrane (together referred to as urinary bladder matrix (UBM)) and ECM harvested from urinary bladder submucosa (UBS). Since the preparation of UBM allows for control of the direction of delamination, the effect of the delamination method on the mechanical behavior of UBM was determined by delaminating the submucosa and other abluminal layers by scraping along the longitudinal axis of the bladder (apex to neck) (UBML) or along the circumferential direction (UBMC). The processing of UBS does not allow for similar directional control. UBML and UBS had similar collagen fiber distributions, with a preferred collagen fiber alignment along the longitudinal direction. UBMC showed a more homogenous collagen fiber orientation. All samples showed a stiffer mechanical behavior in the longitudinal direction. Despite similar collagen fiber distributions, UBML and UBS showed quite different mechanical behavior for the applied loading patterns with UBS showing a much more pronounced toe region. The mechanical behavior for UBMC in both directions was similar to the mechanical behavior of UBML. There are distinct differences in the mechanical behavior of different layers of ECM from the porcine urinary bladder, and the processing methods can substantially alter the mechanical behavior observed.

Gilbert TW; Wognum S; Joyce EM; Freytes DO; Sacks MS; Badylak SF

2008-12-01

315

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

Science.gov (United States)

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.

Yang, C. H.; Yu, Z. Y.; Liu, Y. M.; Lu, P. F.; Gao, T.; Li, M.; Manzoor, S.

2013-10-01

316

Biaxial anisotropy driven asymmetric kinked magnetization reversal in exchange-biased IrMn/NiFe bilayers  

Science.gov (United States)

The significant biaxial anisotropy contribution below 50 K is evidenced and identified as a cause of asymmetric ``kinked'' magnetization reversal behaviour and strong single cycle training effect in ion-beam sputtered IrMn/NiFe bilayers. The minor loop measurement clearly suggests that the magnetization reversal along the descending branch of the hysteresis loop takes place in two distinct steps comprising initial magnetization rotation followed by irreversible domain processes. Our experimental observations of characteristic magnetoresistance and minor loop measurements unambiguously endorse the recent theoretical prediction of Hoffmann suggesting the critical role of the symmetry of antiferromagnetic anisotropy on the reversal asymmetry and training effect.

Fulara, Himanshu; Chaudhary, Sujeet; Kashyap, Subhash C.

2013-07-01

317

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

International Nuclear Information System (INIS)

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

1995-01-01

318

Electro-optic response of the anticlinic, antiferroelectric liquid-crystal phase of a biaxial bent-core molecule with tilt angle near 45?.  

UK PubMed Central (United Kingdom)

We describe the unusual electro-optic response of a biaxial bent-core liquid crystal molecule that exhibits an anticlinic, antiferroelectric smectic phase (Sm-C(A)P(A)) with a molecular tilt angle close to 45°. In the ground state, the sample shows very low birefringence. A weak applied electric field distorts the antiferroelectric ground state, inducing a small azimuthal reorientation of the molecules on the tilt cone. This results in only a modest increase in the birefringence but an anomalously large (?40°) analog rotation of the extinction direction. This unusual electro-optic response is shown to be a consequence of the molecular biaxiality.

Nakata M; Chen D; Shao R; Korblova E; Maclennan JE; Walba DM; Clark NA

2012-03-01

319

A first-principles study on the effect of biaxial strain on the ultimate performance of monolayer MoS2-based double gate field effect transistor  

Science.gov (United States)

In this work, the effect of biaxial strain on the electronic band structure of monolayers of MoS2 is investigated. The effective mass of carriers under different strain values is extracted and the achieved results are discussed. For the first time, we have assessed the effect of biaxial strain on the ultimate performance of MoS2-based double gate field effect transistors (DGFETs). The results indicate that by strain engineering, a significant performance improvement of MoS2-based DGFETs can be achieved.

Mohammad Tabatabaei, Seyed; Noei, Maziar; Khaliji, Kaveh; Pourfath, Mahdi; Fathipour, Morteza

2013-04-01

320

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)

Full Text Available Abstract in spanish 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 (more) 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 Mechanics 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 carrie (more) d 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.

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

2006-12-01

 
 
 
 
321

A continuum damage mechanics model with the strain-based approach to biaxial low cycle fatigue failure  

Energy Technology Data Exchange (ETDEWEB)

A continuum damage mechanics model for low cycle fatigue failure of initially isotropic materials under biaxial loading conditions is presented. The expression for the equivalent strain in the fatigue damage evolution equation contains the three material parameters, and the strain intensity as well as the maximum principal strain and the volume strain for amplitudes. It is shown how these material parameters can be determined from a series of basic experiments using a cruciform specimen. Particular expressions for the equivalent strain with a smaller number of material parameters and invariants are obtained. Model predictions are found to be in satisfactory agreement with the experimental low cycle fatigue data under full ranged biaxial loadings obtained in the test using a cruciform specimen. (orig.) [German] Ein Schadensmodell der Kontinuumsmechanik fuer Ermuedungsbruch nach wenigen Zyklen von urspruenglich isotropen Materialien unter biaxialen Belastungsbedingungen wird vorgestellt. Der Ausdruck fuer die gleichwertige Spannung in der Entstehungsgleichung fuer den Ermuedungsschaden beinhaltet 3 Materialparameter, die Spannungsintensitaet, die maximale Hauptspannung und die Volumenspannungsamplituden. Es wird gezeigt, wie diese Materialparameter durch eine Reihe von grundlegenden Experimenten an einem kreuzfoermigen Materialstueck bestimmt werden koennen. Es ergeben sich eigene Ausdruecke fuer die gleichwertige Spannung mit einer kleineren Anzahl von Materialparametern und -invarianten. Ergebnis ist, dass die Modelvorhersagen in zufriedenstellender Uebereinstimmung mit den experimentellen Daten von Ermuedung nach wenigen Zyklen stehen, die bei variablen vollen biaxialen Betastungen von kreuzfoermigen Materialstuecken erhalten wurden. (orig.)

Zolochevsky, A.; Itoh, T.; Obataya, Y. [Fukui Univ. (Japan). Dept. of Mech. Eng.; Betten, J. [Technische Hochschule Aachen (Germany). Mathematisch-Naturwissenschaftliche Fakultaet

2000-09-01

322

Stress sensitivity of seismic pulse velocity and rise time in a rock-like material  

Energy Technology Data Exchange (ETDEWEB)

The physical model on which the experiments were performed was constructed of three low-strength rock-like materials and had a central rectangular opening representing a coal-mine roadway. It was shown that the seismic pulse rise time is far more sensitive to a change in both uniaxial and biaxial stress fields than is the velocity of pulse propagation. This rise time sensitivity makes the measurement of pulse rise times a promising method for stress surveillance around underground excavations. Rock failure has also been shown to cause a significant increase in the pulse rise time.

Blair, D.P.

1984-08-01

323

The effect of stress state on the hydrogen embrittlement of nickel  

Energy Technology Data Exchange (ETDEWEB)

The ductility of nickel sheet subjected to in situ cathodic hydrogen charging has been investigated over a range of multiaxial stress states including uniaxial, plane-strain, and equibiaxial tension. The extent of ductility loss due to hydrogen increases as the stress state tends from uniaxial to equibiaxial tension. Hydrogen embrittlement is characterized by intergranular fracture with failure due to microcrack formation, microcrack link-up, and macrocrack growth. The increased susceptibility to intergranular embrittlement with increasing biaxiality is a consequence of an enhanced rate of the link-up of strain-induced intergranular microcracks.

Kampe, S.L.; Koss, D.A.

1986-01-01

324

Stress and stress counselling.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 f...

Matheson, K. H.

325

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

Science.gov (United States)

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

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

2012-06-01

326

First- and second-order phase transitions between quantum and classical regimes for the escape rate of a biaxial spin system  

International Nuclear Information System (INIS)

The particle Hamiltonian for a biaxial spin system with a transverse or longitudinal magnetic field is investigated. We apply the Hamiltonian to the quantum-classical escape rate transition in small magnets. It is found that the phase boundary separating the first- and second-order transition is greatly influenced by the transverse anisotropy constant as well as the external magnetic field.

1999-01-01

327

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

UK PubMed Central (United Kingdom)

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

Driscoll TP; Nakasone RH; Szczesny SE; Elliott DM; Mauck RL

2013-06-01

328

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 characteristi...

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

329

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-03-01

330

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

International Nuclear Information System (INIS)

[en] 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

2007-04-07

331

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

Scientific Electronic Library Online (English)

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

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

2012-01-01

332

Comparative analysis of the biaxial mechanical behavior of carotid wall tissue and biological and synthetic materials used for carotid patch angioplasty.  

UK PubMed Central (United Kingdom)

Patch angioplasty is the most common technique used for the performance of carotid endarterectomy. A large number of patching materials are available for use while new materials are being continuously developed. Surprisingly little is known about the mechanical properties of these materials and how these properties compare with those of the carotid artery wall. Mismatch of the mechanical properties can produce mechanical and hemodynamic effects that may compromise the long-term patency of the endarterectomized arterial segment. The aim of this paper was to systematically evaluate and compare the biaxial mechanical behavior of the most commonly used patching materials. We compared PTFE (n? = ?1), Dacron (n ?=? 2), bovine pericardium (n ?= ?10), autogenous greater saphenous vein (n ?= ?10), and autogenous external jugular vein (n ?=? 9) with the wall of the common carotid artery (n ?=? 18). All patching materials were found to be significantly stiffer than the carotid wall in both the longitudinal and circumferential directions. Synthetic patches demonstrated the most mismatch in stiffness values and vein patches the least mismatch in stiffness values compared to those of the native carotid artery. All biological materials, including the carotid artery, demonstrated substantial nonlinearity, anisotropy, and variability; however, the behavior of biological and biologically-derived patches was both qualitatively and quantitatively different from the behavior of the carotid wall. The majority of carotid arteries tested were stiffer in the circumferential direction, while the opposite anisotropy was observed for all types of vein patches and bovine pericardium. The rates of increase in the nonlinear stiffness over the physiological stress range were also different for the carotid and patching materials. Several carotid wall samples exhibited reverse anisotropy compared to the average behavior of the carotid tissue. A similar characteristic was observed for two of 19 vein patches. The obtained results quantify, for the first time, significant mechanical dissimilarity of the currently available patching materials and the carotid artery. The results can be used as guidance for designing more efficient patches with mechanical properties resembling those of the carotid wall. The presented systematic comparative mechanical analysis of the existing patching materials provides valuable information for patch selection in the daily practice of carotid surgery and can be used in future clinical studies comparing the efficacy of different patches in the performance of carotid endarterectomy.

Kamenskiy AV; Pipinos II; MacTaggart JN; Kazmi SA; Dzenis YA

2011-11-01

333

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

International Nuclear Information System (INIS)

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

2011-01-01

334

A new finite-element method simulation model for computing AC loss in roll assisted biaxially textured substrate YBCO tapes  

International Nuclear Information System (INIS)

This paper presents a new finite-element simulation model for computing the electromagnetic properties and AC losses in systems of YBCO (yttrium barium copper oxide) conductors on roll assisted biaxially textured substrates (RABiTS). In this model, the magnetic field dependent permeability and ferromagnetic loss of the substrates in RABiTS YBCO tapes are taken into account. The simulations were employed to simulate the AC loss in stacks of two parallel connected YBCO tapes. The simulation results are compared with the experimental data to check the validity of the simulation model. The result reveals an effective way of significantly reducing AC loss in YBCO tapes by stacking two RABiTS YBCO coated conductors with the appropriate relative tape orientation.

2010-01-01

335

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

DEFF Research Database (Denmark)

This paper proposes a novel, active-flux based, motion-sensorless vector control structure for biaxial excitation generator for automobiles (BEGA) for wide speed range operation. BEGA is a hybrid excited synchronous machine having permanent magnets on q-axis and a dc excitation on daxis. Using the active-flux concept the estimated rotor position is given by the sum of the active flux angle and torque angle. The active flux is calculated by subtracting the term Lq i s from the estimated stator flux vector. The experimental results validate the active flux-principle and show good performance for a speed range of 50 to 2000 rpm. A method for initial rotor position of BEGA is proposed based on injection of a very short voltage pulse in the machine dc excitation, the method being independency of machine parameters. Experimental results for initial rotor position estimation proved accuracy below 10 electrical degrees in less than 2 ms test time.

Coroban-Schramel, Vasile; Boldea, Ion

2009-01-01

336

Caregiver Stress  

Science.gov (United States)

... will not sell or share your name. Caregiver Stress Tweet Bookmark this page | Email | Print Alzheimer's caregivers ... Tips to manage stress 10 symptoms of caregiver stress Caregiver Stress Check Alzheimer caregivers frequently report high ...

337

Manage Stress  

Science.gov (United States)

... Conditions and Diseases > Heart Health > Manage Stress Manage Stress The Basics Take Action! Ver en español Content ... on: July 26, 2013 The Basics Not all stress is bad. Stress can help protect you in ...

338

Handling Stress  

Science.gov (United States)

... with your baby has a soothing effect. Handling stress More information on handling stress Both short and ... stress. Return to top More information on handling stress Explore other publications and websites Breastfeeding FAQs: Sleep — ...

339

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

Energy Technology Data Exchange (ETDEWEB)

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, o

Lundholm, Beatrice

2000-11-01

340

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

International Nuclear Information System (INIS)

[en] 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 a

2000-01-01

 
 
 
 
341

Microplane model for concrete subject to plane stresses  

Energy Technology Data Exchange (ETDEWEB)

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

Gambarova, P.G.; Floris, C.

1986-10-01

342

Microplane model for concrete subject to plane stresses  

International Nuclear Information System (INIS)

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

1986-01-01

343

A New Direct Process to Prepare $YBa_{2}Cu_{3}O_{7-\\gamma}$ films on Biaxially Textured Ag{110}<211>  

CERN Multimedia

YBCO films were successfully prepared on biaxially textured Ag{110} substrates by using pulsed laser deposition. X-ray diffraction results showed that the degree of preferential orientation of Ag{110} substrates varied with increasing annealing temperature. With a thin template layer deposited at low temperature, YBCO film with c-axis orientation and in-plane biaxial alignment could be obtained at high deposition temperature. Scanning electron microscopy observation revealed that YBCO grains enlarged but Ag grains on the surface of the YBCO films became smaller with increasing deposition temperature. At optimal deposition conditions, Ag atoms diffuse into the YBCO grain boundaries, and then fill in the weak-link regions in the YBCO film, resulting in the conduction easier. Jc value of 5?105A/cm2 was obtained at 77K and zero magnetic field for the best YBCO film in our work.

Wang, R; Pan, S; He, M; Chen, Z; Yang, G; Wang, Rongping; Zhou, Yueliang; Pan, Shaohua; He, Meng; Chen, Zhenghao; Yang, Guozhen

1999-01-01

344

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

Science.gov (United States)

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

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

2013-03-01

345

An optimized ultraviolet-A light photodetector with wide-range photoresponse based on ZnS/ZnO biaxial nanobelt.  

UK PubMed Central (United Kingdom)

A novel 1D/1D nanocomposite-based photodetector is successfully fabricated from high-crystalline ZnS/ZnO biaxial nanobelts for the first time. Optimized performance of the ZnS/ZnO nanobelt photodetector is much better than that of pure ZnS or ZnO nanostructures, with a wide-range UV-A light photoresponse, high sensitivity, and very fast response speed.

Hu L; Yan J; Liao M; Xiang H; Gong X; Zhang L; Fang X

2012-05-01

346

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

International Nuclear Information System (INIS)

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

2011-01-01

347

The generation of stress-focusing features in confined elastic sheets  

Science.gov (United States)

Crumpling is the canonical example of stress focusing in a confined elastic sheet. Subject to a large biaxial confinement, the sheet must bend in multiple directions, which induces Gaussian curvature and therefore strain. This strain is best accommodated by focusing the stress into small regions. In a crumpled sheet, multiple stress-focusing features appear apparently randomly. Here, I present two systems in which stress-focusing features are created in a controlled manner. In the first, a thin sheet is floated on a droplet of water. As the curvature of the droplet is increased, first wrinkles and then a focused features appear on the edge of the sheet. In the second, a focused feature appears at the transition between wrinkle patters of two different wavelengths. The degree of the focusing can be controlled by the confinement, the thickness, and the tension applied transverse to the confinement.

Schroll, Robert

2013-03-01

348

Stress Management  

Science.gov (United States)

... Works Teaching Garden Videos About Teaching Gardens Weight Management Body Mass Index (BMI) BMI in Children Losing ... Diet Obesity Childhood Obesity Obesity - Stroke Connection Stress Management How Does Stress Affect You? Fight Stress With ...

349

Cold Stress  

Science.gov (United States)

... Añadir en... Favorites Delicious Digg Google Bookmarks COLD STRESS On This Page Overview Types of Cold Stress ... access to important safety information. Types of Cold Stress Hypothermia | Cold Water Immersion | Frostbite | Trench Foot | Chilblains ...

350

Managing Stress  

Medline Plus

Full Text Available ... when it becomes continuous. Such negative effects can lead to depression and heart disease. This reference summary ... stress.” Risks of Stress Never-ending stress can lead to a variety of diseases. It can lead ...

351

High-cycle and long-life fatigue of 25CrMo4 under multiaxial load conditions by three alternating stresses. Langzeit- und Dauerschwingfestigkeit des Verguetungsstahls 25CrMo4 bei mehrachsiger Beanspruchung durch drei schwingende Lastspannungen  

Energy Technology Data Exchange (ETDEWEB)

Statistically verified experimental results from high-cycle and long-life fatigue tests (HCF and LLF) with altogether 537 unnotched solid cylindrical and thin-walled hollow specimen are demonstrating the fatigue behaviour (S-N-characteritics, scatterband) of 25CrMo4 under uniaxial loading with superimposed static stresses (consideration of the mean stress effect) and under biaxial loadings in variation of phase differences between the three combined normal and torsional stresses {sigma}{sub x}, {sigma}{sub y}, tau{sub xy}. The fatigue strength is commonly decreasing with life time in the high-cycle regime until reaching the fatigue endurance limit in the transition range to infinite life. The 'ductility level' tau{sub W}/{sigma}{sub W} and the 'mean stress sensibility' p=p ({sigma}{sub W}, {sigma}{sub zSch}, R{sub m}) are relatively independent of the intensity by stress amplitudes and fatigue life to failure. In comparison with the specific case of biaxial combined loading with synchroneous amplitudes, the fatigue resistance characteristics are detrimentally influenced by out-of-phase normal stresses {sigma}{sub x}, {sigma}{sub y}; a phase difference of 180deg between the normal stress amplitudes is the most critical state of combination, especially in the lower cycle regime caused by a greater slope coefficient (probability of survival P{sub s}=50%). On the contrary is there in the high-cycle regime as well as in the long-life range no significant influence to the fatigue strength by biaxial load conditions of simultaneously normal stresses with out-of-phase torsional stress tau{sub xy}. (orig.).

Gruen, P.; Troost, A.; Akin, O.; Klubberg, F. (Technische Hochschule Aachen (Germany, F.R.). Lehrstuhl fuer Werkstoffkunde A und Inst. fuer Werkstoffkunde)

1991-03-01

352

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-03-01

353

Evaluation of Flow Stresses of Tubular Materials Considering Material's Anisotropy  

International Nuclear Information System (INIS)

The object of this paper is to evaluate the stress-strain characteristics of tubular materials considering their anisotropic effects by hydraulic bulge tests and tensile tests. In this analytical model. Hill's orthogonal anisotropic theory was adopted for deriving the effective stresses and effective strains under a bi-axial stress state. Annealed C26800 copper tubes were used. The tube thickness at the pole, bulge height and the internal forming pressure were measured simultaneously during the bulge test. The effective stress -- effective strain relations could be determined by those measured values and this analytical model. The flow stress curves of C26800 copper tubes obtained by this approach were compared with those obtained by the tensile test with consideration of material's anisotropy. The finite element method was also adopted to conduct the simulations of hydraulic bulge forming with the flow stress curves obtained by the bulge tests and tensile tests. The analytical forming pressures versus bulge heights were compared with the experimental results to validate the approach proposed in this paper.

2007-05-17

354

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

International Nuclear Information System (INIS)

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.

2011-01-01

355

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

Science.gov (United States)

Adding heat to glass ionomers during setting might improve mechanical properties. The aim was to compare the biaxial flexural strength (BFS) between and within four glass ionomers, by time of exposure to a high-intensity LED light-curing unit. Materials and methods. Samples of Fuji 9 Gold Label, Ketac Molar Easymix, ChemFil Rock, and the EQUIA system were divided into three treatment groups (n = 30): without heating (Group 1), heated with LED lamp of 1400?mW/cm(2) for 30?s while setting (Group 2), and heated with LED lamp of 1400?mW/cm(2) for 60?s while setting (Group 3). Samples were stored for 48 hours in distilled water at 37°C until tested. BFS was tested, using a universal testing machine at a crosshead speed of 1?mm/min. Data were analyzed, using ANOVA test with the Bonferroni correction (? = 0.05). Heating the glass-ionomer cements with an LED curing light of 1400?mW/cm(2) during setting for 30?s increased the BFS value of all GICs. No statistically significant difference in mean BFS scores was found between the EQUIA system and ChemFil Rock at 30?s and 60?s. The mean BFS value was statistically significantly higher for the EQUIA system and ChemFil Rock than for Fuji 9 Gold Label and Ketac Molar Easymix at all exposure times. PMID:23841095

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

2013-06-12

356

Anisotropic reversible aggregation of latex nanoparticles suspended in a lyotropic nematic liquid crystal: effect of gradients of biaxial order.  

Science.gov (United States)

We studied the anisotropic aggregation of spherical latex particles dispersed in a lyotropic liquid crystal presenting three nematic phases: calamitic, biaxial, and discotic. We observed that in the nematic calamitic phase aggregates of latex particles are formed, which become larger and anisotropic in the vicinity of the transition to the discotic phase, due to a coalescence process. Such aggregates are weakly anisotropic and up to 50 microm long and tend to align parallel to the director field. At the transition to the discotic phase, the aggregates dissociated and re-formed when the system was brought back to the calamitic phase. This shows that the aggregation is due to attractive and repulsive forces generated by the particular structure of the nematic phase. The surface-induced positional order was investigated by surface force apparatus experiments with the lyotropic system confined between mica surfaces, revealing the existence of a presmectic wetting layer around the surfaces and oscillating forces of increasing amplitude as the confinement thickness was decreased. We discuss the possible mechanisms responsible for the reversible aggregation of latex particles, and we propose that capillary condensation of the NC phase, induced by the confinement between the particles, could reduce or remove the gradient of order parameter, driving the transition of aggregates from solidlike to liquidlike and gaslike. PMID:19702247

Alves, V M; Nakamatsu, S; Oliveira, E A; Zappone, B; Richetti, P

2009-10-01

357

Anisotropic reversible aggregation of latex nanoparticles suspended in a lyotropic nematic liquid crystal: effect of gradients of biaxial order.  

UK PubMed Central (United Kingdom)

We studied the anisotropic aggregation of spherical latex particles dispersed in a lyotropic liquid crystal presenting three nematic phases: calamitic, biaxial, and discotic. We observed that in the nematic calamitic phase aggregates of latex particles are formed, which become larger and anisotropic in the vicinity of the transition to the discotic phase, due to a coalescence process. Such aggregates are weakly anisotropic and up to 50 microm long and tend to align parallel to the director field. At the transition to the discotic phase, the aggregates dissociated and re-formed when the system was brought back to the calamitic phase. This shows that the aggregation is due to attractive and repulsive forces generated by the particular structure of the nematic phase. The surface-induced positional order was investigated by surface force apparatus experiments with the lyotropic system confined between mica surfaces, revealing the existence of a presmectic wetting layer around the surfaces and oscillating forces of increasing amplitude as the confinement thickness was decreased. We discuss the possible mechanisms responsible for the reversible aggregation of latex particles, and we propose that capillary condensation of the NC phase, induced by the confinement between the particles, could reduce or remove the gradient of order parameter, driving the transition of aggregates from solidlike to liquidlike and gaslike.

Alves VM; Nakamatsu S; Oliveira EA; Zappone B; Richetti P

2009-10-01

358

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

UK PubMed Central (United Kingdom)

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

Fabián Molina G; Cabral RJ; Mazzola I; Brain Lascano L; Frencken JE

2013-01-01

359

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

CERN Multimedia

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...

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

2008-01-01

360

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

International Nuclear Information System (INIS)

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

2006-01-01

 
 
 
 
361

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

Energy Technology Data Exchange (ETDEWEB)

The stress state of Mo layers in Ni/Mo multilayers was investigated and its evolution under ion beam irradiation was monitored using the 'sin{sup 2} {psi}' method. The growth stress in the Mo sub-layers was found to be consistent with a hydrostatic state of stress, accounting for the local deformations due to point defects induced during the sputter growth process. The hydrostatic stress is also responsible for a biaxial stress component appearing in the multilayer that is attached to the substrate, an additional stress component which is superimposed to the coherency stress developed due to epitaxial growth of the multilayers. Ion-irradiation of multilayers results in partial stress relaxation at low fluences, as the growth stress can be almost fully relaxed, while the coherency stresses remain unchanged. That is due to the system's state, the growth stress is far from thermodynamic equilibrium, the coherency stress is close-to-equilibrium. The employed method, combining X-ray diffraction strain analysis and ion irradiation-induced relaxation, in addition to identifying the chemical effects contribution, proved to be a unique tool for recognising and distinguishing stress contributions.

Debelle, A. [Laboratoire de Metallurgie Physique, UMR 6630 CNRS, Universite de Poitiers, Avenue Marie et Pierre Curie, 86962 Futuroscope-Chasseneuil (France); Michel, A. [Laboratoire de Metallurgie Physique, UMR 6630 CNRS, Universite de Poitiers, Avenue Marie et Pierre Curie, 86962 Futuroscope-Chasseneuil (France)]. E-mail: anny.s.michel@univ-poitiers.fr; Abadias, G. [Laboratoire de Metallurgie Physique, UMR 6630 CNRS, Universite de Poitiers, Avenue Marie et Pierre Curie, 86962 Futuroscope-Chasseneuil (France); Jaouen, C. [Laboratoire de Metallurgie Physique, UMR 6630 CNRS, Universite de Poitiers, Avenue Marie et Pierre Curie, 86962 Futuroscope-Chasseneuil (France)

2006-01-15

362

Job Stress  

Science.gov (United States)

Mind/body health: Job stress Jobs and careers are an important part of our lives. Along with providing a source of income, they help us ... are also a major source of emotional stress. Stress at work Even "dream jobs" have stressful deadlines, ...

363

Intergranular stresses in Zircaloy-2 with rod texture  

International Nuclear Information System (INIS)

The intergranular strains in thermally and mechanically anisotropic Zircaloy-2 with rod texture have been measured in situ under uniaxial tension along the rod axis by neutron diffraction. An in-plane biaxial stress state was developed in the grains as deformation proceeded. The tensors describing the stress state of the grains throughout the deformation process have been determined experimentally in the natural crystallographic axes system. After 5% deformation, the stress tensor components of the grains, ?11 and ?33--stresses acting along the left-angle a right-angle-axes and left-angle c right-angle-axes lying in the transverse plane--are 230 ± 20 MPa and -241 ± 21 MPa, respectively. The angular dependence of the initial thermal residual stress state and the final deformed state have also been obtained. The elasto-plastic self-confident model has been used to simulate the experiments and exhibits agreement with experiment. It appears that the introduction of basal slip {0001} left-angle 1 bar 210 right-angle considerably improves the agreement with experiment

1999-01-15

364

Intergranular stresses in Zircaloy-2 with rod texture  

Energy Technology Data Exchange (ETDEWEB)

The intergranular strains in thermally and mechanically anisotropic Zircaloy-2 with rod texture have been measured in situ under uniaxial tension along the rod axis by neutron diffraction. An in-plane biaxial stress state was developed in the grains as deformation proceeded. The tensors describing the stress state of the grains throughout the deformation process have been determined experimentally in the natural crystallographic axes system. After 5% deformation, the stress tensor components of the grains, {sigma}{sub 11} and {sigma}{sub 33}--stresses acting along the {l_angle}a{r_angle}-axes and {l_angle}c{r_angle}-axes lying in the transverse plane--are 230 {+-} 20 MPa and {minus}241 {+-} 21 MPa, respectively. The angular dependence of the initial thermal residual stress state and the final deformed state have also been obtained. The elasto-plastic self-confident model has been used to simulate the experiments and exhibits agreement with experiment. It appears that the introduction of basal slip {l_brace}0001{r_brace}{l_angle}1{bar 2}10{r_angle} considerably improves the agreement with experiment.

Pang, J.W.L.; Mason, T.E. [Univ. of Toronto, Ontario (Canada). Dept. of Physics; Holden, T.M. [National Research Council, Chalk River, Ontario (Canada); Turner, P.A. [AECL, Chalk River, Ontario (Canada). Advanced Materials Research Branch

1999-01-15

365

Bi-axial M-. Phi. analyses of RC columns using fiber model and comparison with experimental results. 2 jikumage wo ukeru hashirabuzai no M-. Phi. kankei eno fiber model no tekigosei  

Energy Technology Data Exchange (ETDEWEB)

In order to examine the accuracy of a fiber model for analyzing the stability of towers of a cable-stayed bridge subjected to biaxial bending force due to earthquake, experimental results of column test specimens were compared with analytical results. The relation between biaxial bending moment and curvature (M-{Phi}) was measured in biaxial bending model experiment using a reinforcement ratio, axial compressive force and loading pattern as parameters. Since the relation was greatly affected by axial modeling of a reinforcing material, the parameter analysis was conducted by paying particular attention to reinforcement models (bilinear model, cubic one and Ramberg-Osgood one). As a result, the Ramberg-Osgood model was suitable for columns with a large longitudinal reinforcement ratio and large axial tension such as seen in highrise buildings, while the cubic model was more suitable for columns with a small ratio such as seen in cable-stayed bridges. 4 refs., 10 figs., 1 tab.

Murayama, Y.; Tokuyama, S.; Furuichi, K. (Kajima Corp., Tokyo (Japan))

1991-10-31

366

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

UK PubMed Central (United Kingdom)

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

Sarman S; Laaksonen A

2012-09-01

367

Development and evolution of biaxial texture of rolled nickel tapes by ion beam bombardment for high T{sub c} coated conductors  

Energy Technology Data Exchange (ETDEWEB)

High quality YBa{sub 2}Cu{sub 3}O{sub 7-x} films on metallic substrates with high critical current densities well over 10{sup 6} A/cm{sup 2} can be prepared by the rolling assisted biaxially textured substrates (RABiTS) method. Nickel or its alloys have been used as biaxially textured substrates formed through a specific rolling and high temperature annealing procedures. In this paper, we report a newly developed process for developing biaxial texture in rolled Ni tape by argon ion beam bombardment. It is named the ion-beam structure modification (ISM) process. In the ISM processed Ni foils, X-ray diffraction {omega} scans showed the full width-half maximum (FWHM) value of the (2 0 0) peak was 5.7 deg. . And the electron back scattering diffraction (EBSP) analysis based on scanning electron microscopy showed good {l_brace}1 0 0{r_brace} <0 0 1> cubic orientation and the mean grain size was determined as about 25 {mu}m. The texture evolution of rolled Ni foils during ISM process is reported also. For ISM process, local temperature elevation and distribution arises from the ion bombardment, coupled with anisotropic incident ion penetration and propagation as a result of channeling effects in the metal lattice, are expected to play the major roles in the development of grain reorientation in the Ni foil. Due to the simplicity and efficiency of the ISM process, the technique shows a great promise for application in the industrial scale production of long-lengths of superconductor tapes.

Wang, S.S.; Wu, K.; Shi, K.; Liu, Q.; Han, Z

2004-08-15

368

Stress–strain relations for hydrogels under multiaxial deformation  

DEFF Research Database (Denmark)

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.

Drozdov, Aleksey; Christiansen, Jesper de Claville

2013-01-01

369

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)

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 (?=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.

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

370

Selective imaging of 3D director fields and study of defects in biaxial smectic A liquid crystals.  

Science.gov (United States)

We report on the selective imaging of different director fields in a biaxial smectic A (SmAb) liquid crystal using Fluorescence Confocal Polarizing Microscopy (FCPM) and Polarizing Microscopy (PM). The patterns of two directors, namely the director n(a) perpendicular to the lamellae and the director n(b) in their planes are visualized by doping the liquid crystal with two fluorescent dyes with different orientation of the transition dipoles with respect to the lamellar matrix. The properties of defects such as disclinations and focal conic domains (FCDs) are consistent with the non-polar D2h-symmetry of the SmA(b) mesophase in the studied mixture of bent-core and rod-like molecules: (1) majority of defects in the director n(b) are half-integer "+/-1/2" disclinations; (2) the integer-strength "+/-1" defects tend to split into the "+/-1/2" disclinations. We compare the vertical cross-sections of the "+/-1" disclinations in the field in SmA(b) and uniaxial nematic samples. In SmA(b), the "+/-1" disclinations do not escape into the third dimension, while in the nematic samples with Schlieren textures they do despite the surface anchoring at the plates; the experimentally determined director field around the escaped disclination capped by a pair of surface point defects--boojums matches the one predicted recently [C. Chiccoli et al., Phys. Rev. E 66, 030701 (2002)]. The FCD structure in SmA(b) is similar to that in SmA and SmC in terms of the normal to the layers but differs significantly in terms of the director n(b) field parallel to the smectic layers. The FCDs in SmA(b) can be associated with topologically non-trivial configurations of n(b) in the surrounding matrix that are equivalent to the disclination lines. PMID:15729509

Smalyukh, I I; Pratibha, R; Madhusudana, N V; Lavrentovich, O D

2005-02-22

371

Selective imaging of 3D director fields and study of defects in biaxial smectic A liquid crystals.  

UK PubMed Central (United Kingdom)

We report on the selective imaging of different director fields in a biaxial smectic A (SmAb) liquid crystal using Fluorescence Confocal Polarizing Microscopy (FCPM) and Polarizing Microscopy (PM). The patterns of two directors, namely the director n(a) perpendicular to the lamellae and the director n(b) in their planes are visualized by doping the liquid crystal with two fluorescent dyes with different orientation of the transition dipoles with respect to the lamellar matrix. The properties of defects such as disclinations and focal conic domains (FCDs) are consistent with the non-polar D2h-symmetry of the SmA(b) mesophase in the studied mixture of bent-core and rod-like molecules: (1) majority of defects in the director n(b) are half-integer "+/-1/2" disclinations; (2) the integer-strength "+/-1" defects tend to split into the "+/-1/2" disclinations. We compare the vertical cross-sections of the "+/-1" disclinations in the field in SmA(b) and uniaxial nematic samples. In SmA(b), the "+/-1" disclinations do not escape into the third dimension, while in the nematic samples with Schlieren textures they do despite the surface anchoring at the plates; the experimentally determined director field around the escaped disclination capped by a pair of surface point defects--boojums matches the one predicted recently [C. Chiccoli et al., Phys. Rev. E 66, 030701 (2002)]. The FCD structure in SmA(b) is similar to that in SmA and SmC in terms of the normal to the layers but differs significantly in terms of the director n(b) field parallel to the smectic layers. The FCDs in SmA(b) can be associated with topologically non-trivial configurations of n(b) in the surrounding matrix that are equivalent to the disclination lines.

Smalyukh II; Pratibha R; Madhusudana NV; Lavrentovich OD

2005-02-01

372

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Adequate polymerization plays an important role on the longevity of the composite resin restorations. OBJECTIVES: The aim of this study was to evaluate the effect of light-curing units, curing mode techniques and storage media on sorption, solubility and biaxial flexural strength (BFS) of a 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 group (more) s (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

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

2012-04-01

373

Effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading.  

UK PubMed Central (United Kingdom)

This study evaluated the effect of air-particle abrasion protocols on the biaxial flexural strength, surface characteristics and phase transformation of zirconia after cyclic loading. Disc-shaped zirconia specimens (Ø: 15mm, thickness: 1.2mm) (N=32) were submitted to one of the air-particle abrasion protocols (n=8 per group): (a) 50?m Al2O3 particles, (b) 110?m Al2O3 particles coated with silica (Rocatec Plus), (c) 30?m Al2O3 particles coated with silica (CoJet Sand) for 20s at 2.8bar pressure. Control group received no air-abrasion. All specimens were initially cyclic loaded (×20,000, 50N, 1Hz) in water at 37°C and then subjected to biaxial flexural strength testing where the conditioned surface was under tension. Zirconia surfaces were characterized and roughness was measured with 3D surface profilometer. Phase transformation from tetragonal to monoclinic was determined by Raman spectroscopy. The relative amount of transformed monoclinic zirconia (FM) and transformed zone depth (TZD) were measured using XRD. The data (MPa) were analyzed using ANOVA, Tukey's tests and Weibull modulus (m) were calculated for each group (95% CI). The biaxial flexural strength (MPa) of CoJet treated group (1266.3±158(A)) was not significantly different than that of Rocatec Plus group (1179±216.4(A,B)) but was significantly higher than the other groups (Control: 942.3±74.6(C); 50?m Al2O3: 915.2±185.7(B,C)). Weibull modulus was higher for control (m=13.79) than those of other groups (m=4.95, m=5.64, m=9.13 for group a, b and c, respectively). Surface roughness (Ra) was the highest with 50?m Al2O3 (0.261?m) than those of other groups (0.15-0.195?m). After all air-abrasion protocols, FM increased (15.02%-19.25%) compared to control group (11.12%). TZD also showed increase after air-abrasion protocols (0.83-1.07?m) compared to control group (0.59?m). Air-abrasion protocols increased the roughness and monoclinic phase but in turn abrasion with 30?m Al2O3 particles coated with silica has increased the biaxial flexural strength of the tested zirconia.

Ozcan M; Melo RM; Souza RO; Machado JP; Felipe Valandro L; Botttino MA

2013-04-01

374

Observation of asymmetric two-taper Vavilov-Cherenkov radiation emitted by relativistic protons when passing along the binormal in biaxial triglycine sulfate crystal  

International Nuclear Information System (INIS)

Directivity and polarization of the Vavilov-Cherenkov radiation when 658 MeV proton transmission along the binormal of biaxial triglycine sulfate are investigated. The radiation is asymmetric relative to the plane, propagating through the beam particle velocity vector perpendicularly to the optical axes plane, and has the form of two symmetric half-tapers with different vertex angles imbedded one in the other. Formulae for the radiation directivity for any angles of the asymmetric two-taper radiation are obtained. The formulae give good agreement with experimental data

1994-01-01

375

Managing Stress  

Medline Plus

Full Text Available ... go differently than you expect. Relax with deep breathing. This is a normal body reaction to stress: ... your mouth, you can counteract the fast, shallow breathing associated with stress. Relax by clearing your mind. ...

376

Managing Stress  

Medline Plus

Full Text Available ... your body, feelings, and behavior? Can you list 7 things that make you feel stressed? Feeling overwhelmed, ... Plain.com hp060103 Last reviewed: 07/14/2010 7 Relax your muscles. Stress causes the muscles to ...

377

Managing Stress  

Medline Plus

Full Text Available ... then agree not to shop together! Plan major lifestyle changes. Many good major changes can exert their ... nutritious meals can help you develop a healthier lifestyle that is conducive to less stress. Managing Stress ...

378

Stress Fractures  

Science.gov (United States)

Stress fractures Basics In-Depth Multimedia Resources Reprints A single copy of this article may be reprinted for personal, noncommercial use only. Stress fractures By Mayo Clinic staff Original Article: http:// ...

379

Managing Stress  

Medline Plus

Full Text Available ... Several studies have associated stress with a weak immune system. The immune system is responsible for fighting diseases and germs that invade the body. With a weakened immune system, a person with chronic stress could become ill ...

380

Managing Stress  

Medline Plus

Full Text Available ... in life. These reactions can have positive or negative effects. Stress has positive effects when it makes ... daily problems and meet the challenges. Stress has negative effects when it becomes continuous. Such negative effects ...

 
 
 
 
381

Stress, Inc.  

Science.gov (United States)

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

Integrated Teaching And Learning Program

382

Thin film polymer stress measurement using piezoresistive anisotropically etched pressure sensors  

Energy Technology Data Exchange (ETDEWEB)

Silicon bulk micromachined piezoresistive pressure sensors are very sensitive to applied stresses: that is, applied pressure and/or packaging-related stresses. Device encapsulation has been observed to affect the electrical output of the pressure sensor significantly. The magnitude of the zero applied pressure output voltage (i.e., the offset voltage) that can be attributed to a thin film encapsulant is proportional to the magnitude of the room-temperature thermal stress of that film. Parylene C coatings have been used as encapsulants in this work. Finite element and analytical modeling techniques were used to evaluate the effect of material property variation on the offset of a pressure sensor. A simple, linear expression of offset as a function of a material property parametric group, that includes: parylene thickness, parylene biaxial modulus, parylene CTE, silicon thickness, and annealing temperature; has been established. Experimental analysis of parylene coated pressure sensors and parylene coated silicon and gallium arsenide wafers was performed to confirm the resulting model. Known variations in parylene material properties caused by processing (i.e., uncontrolled deposition, annealing, and high temperature storage) have been used as an experimental vehicle for this purpose. An empirical relationship between offset voltage on parylene coated devices and room-temperature thermal stress on parylene coated wafers that have been exposed to the same processing is a linear expression with a similar slope to the modeling results. Furthermore, stress measurements from parylene coated silicon wafers and parylene coated gallium arsenide wafers have been used to estimate the parylene biaxial modulus (approximately 5,000 MPa) and the parylene CTE (approximately 0 ppm/C) independently. These material properties were observed to shift following parylene annealing and high temperature storage exposure experiments in a manner that is consistent with the established model.

Bitko, G.; Harries, R.; Matkin, J.; McNeil, A.C.; Monk, D.J.; Shah, M.; Wertz, J. [Motorola, Phoenix, AZ (United States). Sensor Products Div.

1997-05-01

383

Stress at work : stress management  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Shchuka, Aljona

384

An evaluation of the processing conditions, structure, and properties (biaxial flexural strength and antibacterial efficacy) of sintered strontium-zinc-silicate glass ceramics.  

UK PubMed Central (United Kingdom)

The use of artificial bone grafts has increased in order to satisfy a growing demand for bone replacement materials. Initial mechanical stability of synthetic bone grafts is very advantageous for certain clinical applications. Coupled with the advantage of mechanical strength, a material with inherent antibacterial properties would be very beneficial. A series of strontium-doped zinc silicate (Ca-Sr-Na-Zn-Si) glass ceramics have been characterized in terms of their crystalline structure, biaxial flexural strength and antibacterial efficacy based on the identification of optimum sintering conditions. All three glass ceramics, namely, BT110, BT111, and BT112 were found to be fully crystalline, with BT111 and BT112 comprising of biocompatible crystalline phases. The biaxial flexural strengths of the three glass ceramics ranged from 70 to 149 MPa and were shown to be superior to those of clinically established ceramics in dry conditions and following incubation in simulated physiological conditions. The bacteriostatic effect for each glass ceramic was also established, where BT112 showed an inhibitory effect against three of the most common bacteria found at implantation sites, namely, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. The results of the evaluation suggest that the materials studied offer advantages over current clinical materials and indicate the potential suitability of the glass ceramics as therapeutic bone grafts.

Looney M; Shea HO; Gunn L; Crowley D; Boyd D

2013-05-01

385

How to prevent cut-out and cut-through in biaxial proximal femoral nails: is there anything beyond lag screw positioning and tip-apex distance?  

UK PubMed Central (United Kingdom)

PURPOSE: Hip perforation is a major complication in proximal femoral nailing. For biaxial nails, knowledge of their biomechanics is limited. Besides re-evaluation of accepted risk factors like the tip-apex distance (TAD), we analysed the influence of anti-rotational pin length. METHODS: We compared 22 hip perforation cases to 50 randomly chosen controls. TAD, lag-screw position, angle between lag-screw and femoral neck axis, lag-screw gliding capacity, displacement and anti-rotational pin length were investigated. RESULTS: Hip perforation was associated with a higher angle of deviation between lag-screw and femoral neck axis (p = 0.001), a lower telescoping capacity of the lag screw (p = 0.02), and higher TAD (p = 0.048). If the anti-rotational pin exceeded a line connecting the tip of the nail and the lag screw (NS line), hip perforation incidence was increased (p = 0.009). Inadequate pin length resulted in an odds ratio of 10.8 for hip perforation (p = 0.001). CONCLUSIONS: In biaxial nails anti-rotational element positioning is underestimated, however, crucial.

Zirngibl B; Biber R; Bail HJ

2013-07-01

386

The effect of core material, veneering porcelain, and fabrication technique on the biaxial flexural strength and weibull analysis of selected dental ceramics.  

UK PubMed Central (United Kingdom)

PURPOSE: The objective of this study was to compare the effect of veneering porcelain (monolithic or bilayer specimens) and core fabrication technique (heat-pressed or CAD/CAM) on the biaxial flexural strength and Weibull modulus of leucite-reinforced and lithium-disilicate glass ceramics. In addition, the effect of veneering technique (heat-pressed or powder/liquid layering) for zirconia ceramics on the biaxial flexural strength and Weibull modulus was studied. MATERIALS AND METHODS: Five ceramic core materials (IPS Empress Esthetic, IPS Empress CAD, IPS e.max Press, IPS e.max CAD, IPS e.max ZirCAD) and three corresponding veneering porcelains (IPS Empress Esthetic Veneer, IPS e.max Ceram, IPS e.max ZirPress) were selected for this study. Each core material group contained three subgroups based on the core material thickness and the presence of corresponding veneering porcelain as follows: 1.5 mm core material only (subgroup 1.5C), 0.8 mm core material only (subgroup 0.8C), and 1.5 mm core/veneer group: 0.8 mm core with 0.7 mm corresponding veneering porcelain with a powder/liquid layering technique (subgroup 0.8C-0.7VL). The ZirCAD group had one additional 1.5 mm core/veneer subgroup with 0.7 mm heat-pressed veneering porcelain (subgroup 0.8C-0.7VP). The biaxial flexural strengths were compared for each subgroup (n = 10) according to ISO standard 6872:2008 with ANOVA and Tukey's post hoc multiple comparison test (p? 0.05). The reliability of strength was analyzed with the Weibull distribution. RESULTS: For all core materials, the 1.5 mm core/veneer subgroups (0.8C-0.7VL, 0.8C-0.7VP) had significantly lower mean biaxial flexural strengths (p < 0.0001) than the other two subgroups (subgroups 1.5C and 0.8C). For the ZirCAD group, the 0.8C-0.7VL subgroup had significantly lower flexural strength (p= 0.004) than subgroup 0.8C-0.7VP. Nonetheless, both veneered ZirCAD groups showed greater flexural strength than the monolithic Empress and e.max groups, regardless of core thickness and fabrication techniques. Comparing fabrication techniques, Empress Esthetic/CAD, e.max Press/CAD had similar biaxial flexural strength (p= 0.28 for Empress pair; p= 0.87 for e.max pair); however, e.max CAD/Press groups had significantly higher flexural strength (p < 0.0001) than Empress Esthetic/CAD groups. Monolithic core specimens presented with higher Weibull modulus with all selected core materials. For the ZirCAD group, although the bilayer 0.8C-0.7VL subgroup exhibited significantly lower flexural strength, it had highest Weibull modulus than the 0.8C-0.7VP subgroup. CONCLUSIONS: The present study suggests that veneering porcelain onto a ceramic core material diminishes the flexural strength and the reliability of the bilayer specimens. Leucite-reinforced glass-ceramic cores have lower flexural strength than lithium-disilicate ones, while fabrication techniques (heat-pressed or CAD/CAM) and specimen thicknesses do not affect the flexural strength of all glass ceramics. Compared with the heat-pressed veneering technique, the powder/liquid veneering technique exhibited lower flexural strength but increased reliability with a higher Weibull modulus for zirconia bilayer specimens. Zirconia-veneered ceramics exhibited greater flexural strength than monolithic leucite-reinforced and lithium-disilicate ceramics regardless of zirconia veneering techniques (heat-pressed or powder/liquid technique).

Lin WS; Ercoli C; Feng C; Morton D

2012-07-01

387

Effect of furnace type and ceramming heat treatment conditions on the biaxial flexural strength of a canasite glass-ceramic.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To assess the effect of different heat treatment conditions when using two different furnace types on the biaxial flexural strength (BFS) of a fluorcanasite castable glass-ceramic. METHODS: Two furnace types, one a programmable furnace (PF), the other a dental laboratory burnout furnace (DLF), were used with various ceramming times to determine their effect on the BFS of a fluorcanasite castable glass-ceramic. The glass-ceramic material was cast to produce discs of 12 mm diameter and 2 mm thickness using the lost wax casting process (n = 80). After casting, both furnace types were used to ceram the discs. Half the discs were not de-vested from the casting ring before ceramming but cerammed in situ (DLF) and half were de-vested before ceramming (PF). All the discs were given a nucleation heat treatment at 520 degrees C for 1 h and then cerammed at 860 degrees C using four heat soak times (0.5, 1, 2 and 3 h). The DLF furnace had a rate of climb of 13 degrees C/min and the PF furnace had a rate of climb of 5 degrees C/min to 520 degrees C and 3 degrees C/min to 860 degrees C. After ceramming the discs were de-vested and the BFS determined using a Lloyd 2000R tester. RESULTS: The maximum BFS values seen for both furnace types were almost identical (280 MPa), but were achieved at different heat soak times (1 h DLF, and 2 h PF). The only significant differences in BFS values for the two furnaces were between the 0.5 and 2 h heat soak times (p < or = 0.05). Individual differences were seen between results obtained from each furnace type/heat soak times evaluated (p < or = 0.05). SIGNIFICANCE: Already available dental laboratory burnout furnaces can be used to ceram fluorcanasite glass-ceramic castings to the same BFS values as more expensive and slower specialist programmable furnaces.

Johnson A; Shareef MY; van Noort R; Walsh JM

2000-07-01

388

Photosynthesis, stress and stress factors  

Energy Technology Data Exchange (ETDEWEB)

It has been known for many years that the photosynthesis apparatus of plants reacts extremely sensitively to the effects of stress. In this connection, the question as to the way in which stress factors can influence the process of photosynthesis is of interest. The following possibilities are discussed: 1. Immediate influence of the stress factors of the reaction to light. 2. Immediate influence of the stress factor on dark reaction. 3. Indirect effect of the stress factor on the photosynthesis through the sealing of the stomata.

Huber, W.

1985-01-01

389

Method of Dimensioning Stress-Strain State of Steel Concrete Plate  

Directory of Open Access Journals (Sweden)

Full Text Available The steel-concrete constructions experience an increased development this last time. The main advantages are that they ensure the economy of materials, energy and labour. The steel-concrete elements allow a rational use of the concrete in the tensile zone, ensure a reduction of the weight of the building, its cost and also reduce the formwork. The calculations carried out by the authors make it possible to establish the dependence between the constraints and the deformations in the principal directions under a biaxial state of stresses, to obtain the expressions of the principal moments, determine the parameters of the deformations of the concrete Eb, Ebi, ?b, ?bi, obtained through the reduction of the tensile and compressive stresses of the concrete in an isotropic conventional homogeneous state. The expressions of the constraints in the plate are gotten and compared between the theoretical values and the experimental convergence of the results with a variation of less than 8%.

Emmanuel Yamb; Christian A. Bock Hyeng

2013-01-01

390

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

International Nuclear Information System (INIS)

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

2004-02-01

391

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

DEFF Research Database (Denmark)

A filament stretching rheometer was used for measuring the startup of uni-axial elongational flow followed by reversed bi-axial flow, both with a constant elongational strain rate. A narrow molecular mass distribution linear polyisoprene with a molecular weight of 483 kg/mole was subjected to the flow in the non-linear flow regime. This has allowed highly elastic measurements within the limit of pure orientational stress, as the time of the flow was considerably smaller than the Rouse time. A Doi-Edwards [J. Chem. Soc., Faraday Trans. 2 74, 1818-1832 (1978)] type of constitutive model with the assumption of pure configurational stress was accurately able to predict the startup as well as the reversed flow behavior. This confirms that this commonly used theoretical picture for the flow of polymeric liquids is a correct physical principle to apply. c 2010 The Society of Rheology. [DOI: 10.1122/1.3496378

Rasmussen, Henrik K.; Bejenariu, Anca Gabriela

2010-01-01

392

Operator stress  

Energy Technology Data Exchange (ETDEWEB)

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)

Patterson, B.K. [Human Factors Practical, Lepreau, NB (Canada); Bradley, M. [University of New Brunswick, Saint John, NB (Canada); Artiss, W.G. [Human Factors Practical, Lepreau, NB (Canada)

1998-07-01

393

Experimental Study of the Biaxial Cyclic Behavior of Thin-Wall Tubes of NiTi Shape Memory Alloys  

Science.gov (United States)

Combined torsion-tension cycling experiments were performed on thin-wall tubes (with thickness/radius ratio of 1:20, similar to that found for stents) of nearly equiatomic NiTi shape memory alloys (SMAs). Experiments were controlled by axial displacement and torsional angle with step loading involving torsional loading to a maximum strain, followed by tensile loading, and reverse-order unloading. The superelasticity of the material is confirmed by pure torsion and tension experiments at the test temperature. The evolution of equivalent stress-strain curves as well as the separated tensile and torsional stress-strain curves during cycling is analyzed. Results show that the equivalent stress increases greatly with a small amount of applied axial strain, and the equivalent stress-strain curves have negative slopes in the phase transformation region. The shear stress drops when the torsional strain is maintained at its maximum value and the tensile strain is increased. The shear stress increases with decreasing tensile strain, but it cannot recover to the original value after the complete unloading of the tensile strain. Attention is also paid to dissipated energy density and characteristic stress evolutions during cycling.

Wang, X. M.; Zhou, Q. T.; Liu, H.; Deng, C. H.; Yue, Z. F.

2012-11-01

394

[Stress fractures  

UK PubMed Central (United Kingdom)

Stress fractures are common overuse injuries, ranging between 1.1% and 3.7% of all athletic injuries. Causes are many and usually involve repetitive submaximal stress. There is a wide research evidence showing that training errors cause stress fractures in as many as 22% to 75% of cases. Intrinsic factors such as hormonal imbalance may also contribute to the onset of stress fractures, especially in women. During medical examination, it is essential always to bear in mind the possibility of stress fracture. Clinical diagnosis is therefore the basic procedure, followed by other diagnostic methods in the following order: radiology, scintigraphy, and MRI. Most stress fractures are uncomplicated and can be managed through rest and restriction from precipitating activities for 4-6 weeks. A subset of stress fractures can present a high risk for progression to complete fracture, delayed union, or nonunion. Specific sites for this type of stress fracture are the femoral neck, the anterior cortex of the tibia, the tarsal navicular, the fifth metatarsal (Jones fracture), and the great toe sesamoids. Therefore, high-risk stress fractures require aggressive treatment, and in some cases even surgical intervention is appropriate.

Bojani? I; Pe?ina HI; Pe?ina M

2001-12-01

395

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.)

2006-01-01

396

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)

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.

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

2012-09-01

397

Air-particle abrasion on zirconia ceramic using different protocols: effects on biaxial flexural strength after cyclic loading, phase transformation and surface topography.  

UK PubMed Central (United Kingdom)

This study evaluated the effect of different air-particle abrasion protocols on the biaxial flexural strength and structural stability of zirconia ceramics. Zirconia ceramic specimens (ISO 6872) (Lava, 3M ESPE) were obtained (N=336). The specimens (N=118, n=20 per group) were randomly assigned to one of the air-abrasion protocols: Gr1: Control (as-sintered); Gr2: 50 µm Al2O3 (2.5 bar); Gr3: 50 µm Al2O3 (3.5 bar); Gr4: 110 µm Al2O3(2.5 bar); Gr5: 110 µm Al2O3 (3.5 bar); Gr6: 30 µm SiO2 (2.5 bar) (CoJet); Gr7: 30 µm SiO2(3.5 bar); Gr8: 110 µm SiO2 (2.5 bar) (Rocatec Plus); and Gr9: 110 µm SiO2 (3.5 bar) (duration: 20 s, distance: 10 mm). While half of the specimens were tested immediately, the other half was subjected to cyclic loading in water (100,000 cycles; 50 N, 4 Hz, 37 °°C) prior to biaxial flexural strength test (ISO 6872). Phase transformation (t?m), relative amount of transformed monoclinic zirconia (FM), transformed zone depth (TZD) and surface roughness were measured. Particle type (p=0.2746), pressure (p=0.5084) and cyclic loading (p=0.1610) did not influence the flexural strength. Except for the air-abraded group with 110 µm Al2O3 at 3.5 bar, all air-abrasion protocols increased the biaxial flexural strength (MPa) (Controlnon-aged: 1,030 ± 153, Controlaged: 1,138 ± 138; Experimentalnon-aged: 1,307 ± 184-1,554 ± 124; Experimentalaged: 1,308 ± 118-1,451 ± 135) in both non-aged and aged conditions, respectively. Surface roughness (Ra) was the highest with 110 µm Al2O3(0.84 µm. FM values ranged from 0% to 27.21%, higher value for the Rocatec Plus (110 µm SiO2) and 110 µm Al2O3 groups at 3.5 bar pressure. TZD ranged between 0 and 1.43 µm, with the highest values for Rocatec Plus and 110 µm Al2O3 groups at 3.5 bar pressure.

Souza RO; Valandro LF; Melo RM; Machado JP; Bottino MA; Ozcan M

2013-10-01

398

Managing Stress  

Medline Plus

Full Text Available X-Plain Managing Stress Reference Summary Introduction Stress is a physical and emotional reaction that everyone experiences as ... 1995-2010, The Patient Education Institute, Inc. www.X-Plain.com hp060103 Last reviewed: 07/14/2010 1 ...

399

Oxidative stress  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Burton, Graham J.; Jauniaux, Eric

400

Managing Stress  

Medline Plus

Full Text Available ... life. These reactions can have positive or negative effects. Stress has positive effects when it makes us deal constructively with daily problems and meet the challenges. Stress has negative effects when it becomes continuous. Such negative effects can ...

 
 
 
 
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