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1

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

2

A Determination of Dewetting in a Biaxial Stress Field.  

Science.gov (United States)

An experimental investigation of dewetting in uniaxial and biaxial stress fields was conducted for infinitesimal strain levels. An optical technique was attempted with limited success, which demonstrated the need for more precise measurements at small str...

J. R. Juliano

1967-01-01

3

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.

Ali Ziaei Asl

2011-03-01

4

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 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 ...

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

2011-01-01

5

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

Energy Technology Data Exchange (ETDEWEB)

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

Oh, Chang-Young [Department of Mechanical Engineering, Korea University, Anam-Dong, Sungbuk-Ku, Seoul 136-701 (Korea, Republic of); Kim, Yun-Jae, E-mail: kimy0308@korea.ac.kr [Department of Mechanical Engineering, Korea University, Anam-Dong, Sungbuk-Ku, Seoul 136-701 (Korea, Republic of); Budden, Peter [EDF-Energy, Barnwood, Gloucester GL4 3RS (United Kingdom); Ainsworth, Robert A. [University of Manchester, Manchester M13 9PL (United Kingdom)

2011-10-15

6

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

International Nuclear Information System (INIS)

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

2011-10-01

7

Mean stress effects in biaxial fatigue of Inconel 718  

International Nuclear Information System (INIS)

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

1984-01-01

8

An apparatus for measuring bi-axial stresses  

International Nuclear Information System (INIS)

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

1975-01-01

9

Study on thermal fatigue endurance under biaxial stress state  

International Nuclear Information System (INIS)

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

1980-05-23

10

Structural behaviour of ETFE-foils under biaxial stresses  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The doctoral thesis investigates the material and load bearing behaviour of ETFE-foils under biaxial stresses. For this purpose bursting tests of circular ETFE-foils samples are done to analyse the influence of different strain velocities and preloading conditions on the material behaviour of ETFE-foils. For determining the 3D shapes and the material behaviour of ETFE-foils under increasing pressure an especially test stand with a special modular photogrammetric recording and image analysis s...

2009-01-01

11

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

International Nuclear Information System (INIS)

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

1993-01-01

12

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

2010-01-01

13

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

International Nuclear Information System (INIS)

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

1980-12-17

14

Creep modeling of textured zircaloy under biaxial stressing  

International Nuclear Information System (INIS)

Anisotropic biaxial creep behavior of textured Zircaloy tubing was modeled using a crystal-plastic uniform strain-rate upper-bound and a uniform stress lower-bound approach. Power-law steady-state creep is considered to occur on each crystallite glide system by fixing the slip rate to be proportional to the resolved shear stress raised to a power. Prismatic, basal, and pyramidal slip modes were considered. The crystallographic texture is characterized using the orientation distribution function determined from a set of three pole-figures. This method is contrasted with a Von-Mises-Hill phenomenological model in comparison with experimental data obtained at 673 deg K. The resulting creep-dissipative loci show the importance of the basal slip mode on creep in heavily cold-worked cladding, whereas prismatic slip is more important for the recrystallized materials. (author)

1984-01-01

15

Effects of biaxial loading and residual stresses on constraint  

Energy Technology Data Exchange (ETDEWEB)

Finite element analyses have been carried out to determine the elastic stress intensity factors, the plastic limit loads, failure assessment diagrams (FADs) and the T- and Q-stresses for each of three postulated defects. The effect of biaxial loading and residual stresses on the stress intensity factor and T and Q-stress solutions, and the effect of weld-base metal mismatch on the plastic limit load were assessed. Results have also been derived for the reduction in constraint with increasing plasticity up to the limit load. For assessments of a narrow mismatched weld of overmatching strength using standard Option 1 or 2 FADs, up to L{sub r}=1, this parameter should be determined using the lower strength base material yield strength. The decrease in constraint with increasing L{sub r} varies at different positions around the crack front of semi elliptical surface defects. Although constraint is maintained highest just under the free surface towards the ends of the crack, this is generally the region where the stress intensity factor is lowest for tension loading and thus assessments need to take account of both crack tip driving force and constraint.

Burdekin, F.M.; Xu, W.G

2003-11-01

16

Effects of biaxial loading and residual stresses on constraint  

International Nuclear Information System (INIS)

Finite element analyses have been carried out to determine the elastic stress intensity factors, the plastic limit loads, failure assessment diagrams (FADs) and the T- and Q-stresses for each of three postulated defects. The effect of biaxial loading and residual stresses on the stress intensity factor and T and Q-stress solutions, and the effect of weld-base metal mismatch on the plastic limit load were assessed. Results have also been derived for the reduction in constraint with increasing plasticity up to the limit load. For assessments of a narrow mismatched weld of overmatching strength using standard Option 1 or 2 FADs, up to Lr=1, this parameter should be determined using the lower strength base material yield strength. The decrease in constraint with increasing Lr varies at different positions around the crack front of semi elliptical surface defects. Although constraint is maintained highest just under the free surface towards the ends of the crack, this is generally the region where the stress intensity factor is lowest for tension loading and thus assessments need to take account of both crack tip driving force and constraint

2003-11-01

17

Creep, stress relaxation and biaxial ratchetting of type 304 stainless steel after cyclic preloading  

International Nuclear Information System (INIS)

A series of tests for creep, stress relaxation, and biaxial ratchetting of type 304 stainless steel after cyclic preloading were carried out to investigate their interaction. The interesting fact was pointed out that back stress in cyclic plasticity played an important role to describe creep, relaxation, and biaxial ratchetting following cyclic preloading. Then, the test results showed that the material behavior due to creep after cyclic preloading could be represented by the modified Bailey-Norton law with stress levels evaluated from the current center of the yield surface, i.e., back stress which was determined by the hybrid constitutive model for cyclic plasticity proposed by the authors. In addition, biaxial ratchetting of axial strain induced by cyclic shear straining after cyclic preloading was expressed by the shear stress amplitude, the number of cycle and the axial stress level from the current center

1994-04-01

18

Phonon deformation potentials of hexagonal GaN studied by biaxial stress modulation  

Directory of Open Access Journals (Sweden)

Full Text Available In this work, a biaxial stress modulation method, combining the microfabrication technique, finite element analysis and a weighted averaging process, was developed to study piezospectroscopic behavior of hexagonal GaN films, epitaxially grown by metalorganic chemical vapor deposition on c-sapphire and Si (111 substrates. Adjusting the size of patterned islands, various biaxial stress states could be obtained at the island centers, leading to abundant stress-Raman shift data. With the proposed stress modulation method, the Raman biaxial stress coefficients of E2H and A1 (LO phonons of GaN were determined to be 3.43 cm-1/GPa and 2.34 cm-1/GPa, respectively.

Jun-Yong Lu

2011-08-01

19

Acoustic Emission under Biaxial Stresses in Unflawed 21-6-9 and 304 Stainless Steel.  

Science.gov (United States)

Acoustic emission (AE) testing has been carried out with uniaxial and biaxial (2:1 stress ratio) stressing of smooth samples of 21-6-9 and 304 stainless steel (SS). Uniaxial testing was done with simple tensile and compression samples as well as with the ...

M. A. Hamstad E. M. Leon A. K. Mukherjee

1980-01-01

20

Martensitic transformation in Ni-Al - the effect of biaxial stress  

International Nuclear Information System (INIS)

Full text: Previous work on a Ni0.625Al0.375 crystal has shown that there are significant differences between the thermal expansion behaviour in three different directions. The current work focuses on the effect of an applied biaxial stress in one of these [100] directions. Measurements taken using a capacitance dilatometer show that the applied stress has a dramatic effect on the thermal expansion properties of the crystal. The most obvious effect in a single [100] direction can be seen upon cooling through the martensitic transformation temperature. The unstressed crystal exhibits negative strain at Ms (the martensite start temperature) while the biaxially stressed crystal undergoes a positive strain at Ms. The martensitic transformation has also been observed using optical microscopy. In the absence of the biaxial stress, the strain associated with the martensitic transformation is accommodated by extensive cracking of the crystal. When the biaxial stress is applied, the cracking is much less severe and the martensitic transformation more uniform in appearance

1998-02-03

 
 
 
 
21

Effect of biaxial stresses on iodine SCC behavior of zircaloy fuel cladding tubes  

International Nuclear Information System (INIS)

The experimental apparatus developed for the biaxial SCC test and the deformation properties obtained under predetermined stress are described. The conclusions are: (1) Fracture of Zircaloy-2 cladding tubes under argon environment occurs after passing through the maximum loading point. Under iodine environment, however, the maximum loading point and decreasing load are followed by fracture under uniaxial tension, but fracture occurs during increasing load under biaxial tension. (2) Fracture ductilities for all stress ratios under the iodine environment are lower than those under argon. (3) Over the range of stress ratios in which tangential stress is larger than axial stress, fracture ductility for the argon environment is sensitive to the stress ratio. Under the iodine environment, however, the effective fracture elongation varies from about 5 to 8%. (orig.)

1982-01-01

22

Numerical Validation of Analytical Biaxial True Stress--True Strain Curves from the Bulge Test  

Science.gov (United States)

The present investigation deals with the validation of the experimentally obtained biaxial true stress--true strain curves of the HCT 780 C sheet material from the bulge test with the help of the FEA. Furthermore the investigation handles the consideration of the bending influence via the blank curvature evaluation with an optical measurement system Gom ARAMIS.

Vucetic, M.; Bouguecha, A.; Peshekhodov, I.; Götze, T.; Huinink, T.; Friebe, H.; Möller, T.; Behrens, B.-A.

2011-08-01

23

Residual stresses in biaxially fatigued austenitic stainless steel sample of cruciform geometry  

Science.gov (United States)

A specifically designed cruciform-shaped austenitic stainless steel AISI 321 sample was subjected to ex-situ biaxial tension-compression cycling to establish ferromagnetic martensitic phase conversion under the action of plastic deformation. The time-of-flight neutron diffraction technique was employed for in-plane residual stress determination in this sample for both the austenitic and martensitic phases. The 2D data enabled determination of macro-, micro-, hydro- and deviatoric contributions to the total phase stresses.

Taran, Yu V.; Balagurov, A. M.; Schreiber, J.; Evans, A.; Venter, A. M.

2012-02-01

24

Residual stresses in biaxially fatigued austenitic stainless steel sample of cruciform geometry  

International Nuclear Information System (INIS)

A specifically designed cruciform-shaped austenitic stainless steel AISI 321 sample was subjected to ex-situ biaxial tension-compression cycling to establish ferromagnetic martensitic phase conversion under the action of plastic deformation. The time-of-flight neutron diffraction technique was employed for in-plane residual stress determination in this sample for both the austenitic and martensitic phases. The 2D data enabled determination of macro-, micro-, hydro- and deviatoric contributions to the total phase stresses.

2012-02-08

25

Residual stresses in biaxially fatigued austenitic stainless steel sample of cruciform geometry  

International Nuclear Information System (INIS)

A specifically designed cruciform-shaped austenitic steel AISI 321 sample was subjected to ex-situ biaxial tension-compression cycling to establish ferromagnetic martensitic phase conversion under the action of plastic deformation. The time-of-flight neutron diffraction technique was employed for in-plane residual stress determination in this sample for both the austenitic and martensitic phases. The 2D data enabled determination of the macro-, micro, hydro- and deviatoric contributions to the total phase stresses

2011-01-01

26

Optimization of magnetic properties of Co/Pd multilayers by applying a large persistent biaxial stress  

Science.gov (United States)

We report about optimization of the effective perpendicular magnetic anisotropy (Keff) of [Pd(0.98 nm)/Co(t nm)]30 multilayers by applying an in-plane biaxial tensile stress by loading the Ta substrate with hydrogen. The stress induced anisotropy enhances the Keff, which in turn increases the coercive field and the squareness of the perpendicular magnetization curves. A quantitative analysis of the data using a simple model yields magnetostriction constants for the [Pd(0.98 nm)/Co(t nm)]30 multilayers which are in good agreement with the literature values. We conclude that the Keff can be significantly enhanced by applying persistent in-plane biaxial tensile stress.

Mohanan, Senthilnathan; Herr, Ulrich

2007-11-01

27

Knockdown Factors for Buckling of Cylindrical and Spherical Shells Subject to Reduced Biaxial Membrane Stress  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Cylindrical shells under uniaxial compression and spherical shells under equi-biaxial compression display the most extreme buckling sensitivity to imperfections. In engineering practice, the reduction of load carrying capacity due to imperfections is usually addressed by use of a knockdown factor to lower the critical buckling stress estimated or computed without accounting for imperfections. For thin elastic cylindrical shells under uniaxial compression and spherical shells under equi-biaxia...

2010-01-01

28

Numerical analysis of interacting cracks in biaxial stress field  

International Nuclear Information System (INIS)

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

1999-09-06

29

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

International Nuclear Information System (INIS)

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

1978-06-29

30

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

Scientific Electronic Library Online (English)

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

José Marcio F., Calixto.

31

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

International Nuclear Information System (INIS)

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

2012-05-30

32

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

33

Effect of mono-tension and biaxial tension on microstructure and stress corrosion cracking of Alloy 690TT  

International Nuclear Information System (INIS)

The grain boundary misorientation and dislocation structure for Alloy 690TT under mono-tension and biaxial tension at room temperature was investigated by using electron backscatter diffraction technique (EBSD) and transmission electron microscopy (TEM). The strain amplitudes for mono-axial tension were X3%, X5%, X7% and X9% respectively, and biaxial tension followed X3%, X5%, Y3%, X7%, Y7%, X9%, and Y9% tensile strains. The results showed that the mono-tension could decrease the amount of ?3 twin boundaries, increased the amount of the low angle boundary and random grain boundary. The biaxial tension recovered some random boundaries partially back to ?3 boundaries. Tension strains in Y direction restricted the decease of ?3 boundaries. For the mono-tension specimen the dislocation had high energy pile-ups structure and for the biaxial tension specimen had low energy tangle structure. According to mechanochemical effect theory, the biaxial tension could retard stress corrosion cracking of Alloy 690TT.

2009-08-25

34

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

International Nuclear Information System (INIS)

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

1992-01-01

35

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

International Nuclear Information System (INIS)

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

2010-05-01

36

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

International Nuclear Information System (INIS)

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

1998-01-01

37

Analyses of Failure Mechanisms and Residual Stresses in Graphite/Polyimide Composites Subjected to Shear Dominated Biaxial Loads  

Science.gov (United States)

This research contributes to the understanding of macro- and micro-failure mechanisms in woven fabric polyimide matrix composites based on medium and high modulus graphite fibers tested under biaxial, shear dominated stress conditions over a temperature range of -50 C to 315 C. The goal of this research is also to provide a testing methodology for determining residual stress distributions in unidirectional, cross/ply and fabric graphite/polyimide composites using the concept of embedded metallic inclusions and X-ray diffraction (XRD) measurements.

Kumosa, M.; Predecki, P. K.; Armentrout, D.; Benedikt, B.; Rupnowski, P.; Gentz, M.; Kumosa, L.; Sutter, J. K.

2002-01-01

38

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

1993-08-16

39

Mechanical behavior of irradiated 20% cold-worked Type 316 stainless steel subjected to a biaxial stress state  

International Nuclear Information System (INIS)

The recently developed Controlled Biaxial Rate (CBSR) test system was used to perform constant temperature, constant diametral strain rate tests on fast reactor cladding. The CBSR test is analogous to conventional uniaxial tests; however, the CBSR stress state is more prototypic of in-reactor transient conditions. Results from CBSR testing of irradiated 20% cold worked Type 316 stainless steel cladding of Fast Flux Test Facility (FFTF) geometry are reported for specimens irradiated in the Experimental Breeder Reactor-II (EBR-II) at temperatures from 370 to 680_0C and fluences to 1.3 x 10_2_3 n/cm_2. Tests were performed at constant diametral strain rates between 10"-_5/s and 10"-_3/s at constant test temperature ranging from 400 to 700_0C

1983-04-11

40

The Equi-Biaxial Fatigue Characteristics of EPDM under True (Cauchy) Stress Control Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

ABSTRACT: Strain amplitude control is most often employed when carrying out fatigue testing of rubber components. Often the design engineer requires fatigue test data that is based on load amplitude control. This is analogous to engineering or nominal stress amplitude control. This usually makes it easy to maintain the load within the specified test limits during extended testing. Values of true stress and strain can be obtained from this approach, but the magnitudes of the maximum true stres...

2013-01-01

 
 
 
 
41

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

Science.gov (United States)

An instrumented and highly integrated biaxial stretching system was designed and constructed to obtain true stress, true strain, and optical behavior of polymeric films during biaxial stretching. With programmable drive motors, any form of temporally varying biaxial deformation profiles, including linear, exponential, logarithmic as well as cyclic, can be applied to a square-shaped films. This machine allows the investigation of mechano-optical behavior of films under profiles captured in industrial processes. To overcome the edge effects, the samples are painted with a dot pattern that is imaged using a high speed video capture system. This system accurately determines the locations of the each dot matrix in subsequent images acquired and calculates the true strains in both directions. The in-plane optical retardation is determined using spectral birefringence method that uses polarized white light and optical spectrometer in the optical train. This is carried out automatically at less than 10 nm in retardation resolution with the light beam passing through the symmetry center of the sample. Out of plane retardation is measured with an identical optical train tilted 45° to the plane of the film with its light beam going through the same spot on the sample as 0° beam. The true stress and birefringences are calculated with the determined instantaneous thickness of the film. With this system, the stress optical behavior of PET's is determined up to very large deformation levels at moderate to high deformation rates. Beyond the initial linear stress optical behavior, these films exhibit sudden positive deviation from linearity and this start of nonlinearity was directly associated with the stress induced crystallization. PMID:23277999

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

2012-12-01

42

Dynamic uniaxial and biaxial stress-strain relationships for austenitic stainless steels  

International Nuclear Information System (INIS)

Fast breeder containment structures could be subjected to explosive accidents and impact of missiles, which give rise to propagation and successive reflections of tension waves which deform the material at constant or changing strain rate, with load release and reloading eventually in compression, along multiaxial directions. Constitutive equations, required for calculation codes, should be able to describe the behaviour of the material under these different dynamic loading conditions. In order to provide an experimental basis to the formulation of the constitutive equations, we have developed a hydropneumatic machine and a Hopkinson bar with which we determined the stress-strain curves for austenic stainless steels (AISI 304L, AISI 316L) at constant strain rates ranging from 10"2s"-"1 to 10"3s"-"1, in uniaxial tension. From these tests we observed that the main effects of strain rate on the dynamic flow curves of these steels at room temperature are the substantial increase of the flow stress and the marked reduction of ductility with increasing strain rate. (orig.)

1979-08-21

43

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

44

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

Energy Technology Data Exchange (ETDEWEB)

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

Singh, Ranber; Bester, Gabriel [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Ding, Fei; Plumhof, Johannes; Zander, Tim; Rastelli, Armando; Schmidt, Oliver [Institute for Integrative Nanosciences, IFW Dresden, Dresden (Germany)

2010-07-01

45

Comparison of determination of biaxial true stress - true strain curves by the use of plane strain compression test and bulge test  

Science.gov (United States)

The true stress-strain curve of the common uniaxial tensile test delivers data only within the uniform elongation. Beyond the instability point, the flow curve is usually extrapolated by different the mathematical approaches. Due to the different mathematical approaches, the extrapolated flow curve shows different curve shapes. A more accurate extrapolation can be achieved with the help of a different test, which enables an experimental determination of true stress - true strain curves at higher strain values. In this paper the biaxial true stress - true strain curves determined with the aid of a newly developed plane strain compression test for thin sheets are presented and compared with the results of the bulge test for the same material.

Behrens, B.-A.; Hübner, S.; Bouguecha, A.; Grbic, N.; Vucetic, M.

2013-12-01

46

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

47

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

48

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

49

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-A_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_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

1995-07-23

50

Biaxial creep of zircaloy cladding  

International Nuclear Information System (INIS)

Zircaloy is widely used as the tubing material to clad radioactive fuel in light water reactors. A knowledge of the creep characteristics of zircaloy fuel cladding under biaxial loading is essential in reliably predicting the dimensional changes of the tubing during service. The paper summarizes the various experimental techniques used in measuring in-situ the hoop and axial creep strains during thermal creep of zircaloy fuel cladding subjected to internal pressurization and axial loading simultaneously. The results described in the paper would relate to cold-worked stress-relieved tubing and the general creep equations developed from these correlations can be extended to materials with different crystallographic textures by properly accounting for the creep anisotropy. The temperature and stress dependencies of the steady-state creep-rate were described by Dorn equation: ?sub(theta)sup(s); ckT/Deb =A exp B(?sub(theta)/E), where D is the self-diffusion coefficient, E the elastic modulus, b Burgers vector and A and B are material constants which also depend on the stress state. Biaxial creep results as a function of the stress ratio (?_?/?_z) enabled an evaluation of creep locus based on the hypothesis of an invariant creep potential. The results were correlated with the Von-Mises-Hill phenomenological description with appropriate anisotrophy parameters (R and P). The effect of partial recrystallization on creep anisotropy is described using the literature data. The steady-state creep model-equations were extended to describe the creep transients using short-term anelastic deformation. The model equations were shown to predict the observed transients quite well; the model accurately predicted the negative creep following stress drops as well as short normal creep due to stress increases. (author)

1986-08-01

51

Effects of biaxial state of stress on grain size composition of mined coal in the Lublin coal basin  

Energy Technology Data Exchange (ETDEWEB)

Evaluates effects of mechanical properties of black coal seams mined in the Bogdanka mine in the Lublin black coal basin on coal comminution during longwall mining by shearer loaders. Effects of strata control systems, yield strength of powered supports, cutting depth and other factors on coal comminution are discussed. Samples of black coal from a number of coal seams with differing mechanical properties were cut under laboratory conditions modeling mining at depths close to 1,000 m with high rock strata stresses. Coal compression strength ranged from 6 to 26 MPa, coal workability coefficient from 0.79 to 1.18, coal compactness coefficient from 0.8 to 2.13. Recommendations for cutting schemes and strata control methods are made. 7 refs.

Jonak, J.; Paszkowski, Z. (Politechnika Lubelska (Poland). Katedra Mechanizacji Gornictwa)

1990-01-01

52

Planar Biaxial Behavior of Fibrin-Based Tissue-Engineered Heart Valve Leaflets  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To design more effective tissue-engineered heart valve replacements, the replacement tissue may need to mimic the biaxial stress–strain behavior of native heart valve tissue. This study characterized the planar biaxial properties of tissue-engineered valve leaflets and native aortic valve leaflets. Fibrin-based valve equivalent (VE) and porcine aortic valve (PAV) leaflets were subjected to incremental biaxial stress relaxation testing, during which fiber alignments were measured, over a ran...

Robinson, Paul S.; Tranquillo, Robert T.

2009-01-01

53

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

Science.gov (United States)

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

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

1986-01-01

54

Biaxial Yield Surface Investigation of Polymer-Matrix Composites  

Directory of Open Access Journals (Sweden)

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

Zhengjia He

2013-03-01

55

Biaxial fatigue of mild steel; data compilation and analysis  

International Nuclear Information System (INIS)

Design of pressure vessels, including components of nuclear reactors, where loading varies periodically during service, requires an estimate of fatigue life for conditions of biaxial stress. The ASME pressure vessel code, does this by the use of the maximum shear criterion, modified to include the strain dependence of fatigue behaviour. However, since the ASME code was developed a number of authors have reported biaxial fatigue data which are more accurately described by various other criteria. This study attempts to generate a relationship that describes a broad range of published biaxial fatigue data and to review the accuracy of the ASME code fatigue criterion. This paper describes a study of performed at the University of Waterloo which combined data from nine investigations of fatigue of mild steels at room temperature under fully-reversed, biaxial, stress or strain controlled, conditions. This assemblage of some 260 data points covers the fatigue life range from 10 to 107 cycles. Biaxial stress ratios, from equibiaxial (+1) to torsional (-1) are represented. By combining data a broad view of the effect of biaxiality on fatigue is obtained. Areas where data are scant or show inconsistencies become apparent and conclusions drawn have more general applicability than those based on a single investigation. (Auth.)

1975-09-01

56

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

57

Biaxial Creep Specimen Fabrication  

Energy Technology Data Exchange (ETDEWEB)

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.

JL Bump; RF Luther

2006-02-09

58

Biaxial vasoactivity of porcine coronary artery.  

Science.gov (United States)

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. PMID:22427520

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

2012-05-15

59

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

International Nuclear Information System (INIS)

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

1992-03-23

60

Low-cycle fatigue behaviour and microstructure of copper and alpha-brass under biaxial load paths  

International Nuclear Information System (INIS)

The low-cycle fatigue behaviour of copper and a-brass CuZn30 was investigated in uniaxial and biaxial tests. Planar biaxial fatigue tests were carried out using cruciform samples with proportional stain paths with and without phase shift between the two axes. Microcharacterisation was performed by electron microscopy as well as by high-resolution X-ray line profile analysis. The biaxial cyclic stress-strain curves show good agreement with the uniaxial ones using the von Mises equivalent strain hypothesis. The dislocation densities and microhardness values of the biaxial case, however, show significantly lower values compared to the uniaxial case at equivalent von Mises stresses.

2010-07-01

 
 
 
 
61

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

International Nuclear Information System (INIS)

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

2005-01-15

62

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

Energy Technology Data Exchange (ETDEWEB)

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

Genzel, Ch. [Hahn-Meitner-Institut Berlin c/o BESSY II, Albert-Einstein-Str. 15, 12489 Berlin (Germany)]. E-mail: genzel@hmi.de; Klaus, M. [Hahn-Meitner-Institut Berlin c/o BESSY II, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Denks, I. [Hahn-Meitner-Institut Berlin c/o BESSY II, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Wulz, H.G. [EADS Astrium GmbH, Future Programs and Missions, 88039 Friedrichshafen (Germany)

2005-01-15

63

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

2012-01-01

64

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

CERN Multimedia

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

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

2004-01-01

65

Biaxial fatigue of mild steel; data compilation and analysis  

International Nuclear Information System (INIS)

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

1975-09-05

66

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

67

Biaxiality of chiral liquid crystals  

International Nuclear Information System (INIS)

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

1993-01-01

68

Biaxial tension tests of HERF 304L stainless steel. [High Energy-release Rate Forged (HERF)  

Energy Technology Data Exchange (ETDEWEB)

High strength (100 ksi) High Energy-release Rate Forged (HERF) 304L stainless steel is being considered for future weapon components. The potential yield anisotropy of this HERF 304L stainless steel was investigated via biaxial loading experiments. Biaxial tensile tests with proportional loading were performed on thin-walled tubular specimens using internal pressure and axial load. Results of these tests revealed significant yield strength anisotropy in the forgings. As a consequence, traditional isotropic yield criteria, such as the von Mises or Tresca theories, were not representative of the forged strengths. Yield strengths in a biaxial stress state with a stress ratio sigma/sub theta//sigma/sub z/ = 2 were 20% less than that calculated by the von Mises criteria and the axial yield strength. A stress ratio of sigma/sub theta//sigma/sub z/ = 2 is similar to the anticipated service-induced stress state for the forged component.

Hughes, D.A.

1984-01-01

69

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

Directory of Open Access Journals (Sweden)

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

Shimizu I.

2010-06-01

70

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

Science.gov (United States)

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

Jackson, Wade C.; Ratcliffe, James G.

2013-01-01

71

High Temperature Slow Crack Growth of Si3N4 Specimens Subjected to Uniaxial and Biaxial Dynamic Fatigue Loading Conditions  

Science.gov (United States)

The slow crack growth of a hot-pressed silicon nitride was determined at 1300 C in air using dynamic fatigue testing under both uniaxial and biaxial stress states. Good agreement in fatigue parameter exists between the data obtained from uniaxial and biaxial loading conditions. A reasonable prediction of dynamic fatigue from one stress state to another was made using the recently developed CARES/LIFE computer code.

Choi, Sung R.; Nemeth, Noel N.; Salem, Jonathan A.; Powers, Lynn M.; Gyekenyesi, John P.

1995-01-01

72

Biaxial wheel/hub test facility. Proceedings  

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-07-01

73

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

74

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

75

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

1998-07-26

76

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

77

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

78

Inelastic Effects of Biaxial Excitation on Geometrically Asymmetric Plan Building with Biaxial Eccentricity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Seismic analysis is generally performed by creating a structural model which is excited with forces in two orthogonal directions separately i.e. they are subjected to uniaxial excitation. But an actual earthquake will have its effect in both the directions simultaneously. Limited research has been carried out on effect of such biaxial excitation on two way geometrically asymmetric plan having biaxial eccentricity. This paper deals with the inelastic effect of biaxial excitation on non-linear ...

2013-01-01

79

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-09-15

80

Biaxial mechanical modeling of the small intestine.  

Science.gov (United States)

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

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

2011-11-01

 
 
 
 
81

Failure properties of passive human aortic tissue. II--Biaxial tension tests.  

Science.gov (United States)

Descending mid-thoracic aortas were obtained from 16 autopsies and biaxial inflation tests performed on the tissue at dynamic (approximately 20 s-1) and quasi-static (approximately 0.01 s-1) strain rates. A bubble inflation technique was developed for this purpose. Extension histories of the specimens were recorded photographically and values of ultimate stresses and extension ratios in biaxial stretch have been calculated. Under conditions of uniform biaxial stretch the tissue consistently failed in a direction perpendicular to the long axis of the aorta and pressure values at failure were greater by a factor of two in the dynamic tests than those in the quasi-static tests. PMID:6833308

Mohan, D; Melvin, J W

1983-01-01

82

Biaxial tension on polymer in thermoforming range  

Directory of Open Access Journals (Sweden)

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

Billon N.

2010-06-01

83

Biaxial Loading Tests for steel containment vessel  

International Nuclear Information System (INIS)

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)

1999-07-01

84

Neutron diffraction investigation of an in-plane biaxial fatigued stainless steel sample of cruciform geometry  

Science.gov (United States)

Fatigue and fracture under multiaxial stresses are among the most important current research topics aimed at ensuring improved reliability of industrial components. An ex situ in-plane biaxial low cycle fatigued sample of cruciform geometry from austenitic stainless steel AISI 321 H was investigated on the FSD stress-diffractometer at the IBR-2 pulsed nuclear reactor by using the neutron strain scanner and the uniaxial stress rig. The phase composition of fatigued material was determined and the residual macrostresses and phase microstresses were measured. To the best of our knowledge, no neutron diffraction investigations of materials subjected to biaxial loading have been previously carried out. The first results of the neutron diffraction experiment are presented and discussed.

Taran, Yu V.; Balagurov, A. M.; Sheverev, S. G.; Schreiber, J.; Korsunsky, A. M.; Vorster, W. J. J.; Bomas, H.; Stoeberl, C.

2008-03-01

85

Neutron diffraction investigation of an in-plane biaxial fatigued stainless steel sample of cruciform geometry  

Energy Technology Data Exchange (ETDEWEB)

Fatigue and fracture under multiaxial stresses are among the most important current research topics aimed at ensuring improved reliability of industrial components. An ex situ in-plane biaxial low cycle fatigued sample of cruciform geometry from austenitic stainless steel AISI 321 H was investigated on the FSD stress-diffractometer at the IBR-2 pulsed nuclear reactor by using the neutron strain scanner and the uniaxial stress rig. The phase composition of fatigued material was determined and the residual macrostresses and phase microstresses were measured. To the best of our knowledge, no neutron diffraction investigations of materials subjected to biaxial loading have been previously carried out. The first results of the neutron diffraction experiment are presented and discussed.

Taran, Yu V; Balagurov, A M; Sheverev, S G [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Schreiber, J [Fraunhofer Institute for Nondestructive Testing (Dresden branch) (Germany); Korsunsky, A M; Vorster, W J J [Department of Engineering Science, University of Oxford (United Kingdom); Bomas, H; Stoeberl, C [Division of Material Science, Foundation Institute for Materials Science, Bremen (Germany)], E-mail: taran@nf.jinr.ru

2008-03-12

86

Neutron diffraction investigation of an in-plane biaxial fatigued stainless steel sample of cruciform geometry  

International Nuclear Information System (INIS)

Fatigue and fracture under multiaxial stresses are among the most important current research topics aimed at ensuring improved reliability of industrial components. An ex situ in-plane biaxial low cycle fatigued sample of cruciform geometry from austenitic stainless steel AISI 321 H was investigated on the FSD stress-diffractometer at the IBR-2 pulsed nuclear reactor by using the neutron strain scanner and the uniaxial stress rig. The phase composition of fatigued material was determined and the residual macrostresses and phase microstresses were measured. To the best of our knowledge, no neutron diffraction investigations of materials subjected to biaxial loading have been previously carried out. The first results of the neutron diffraction experiment are presented and discussed

2008-03-12

87

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

88

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

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

2012-01-01

89

Mean strain effect on crack initiation lives for notched specimens under biaxial nonproportional loading paths  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses the mean strain effect on the crack initiation lives for notched specimens under biaxial nonproportional loading paths. Elastic-plastic finite element method was used to evaluate the local stresses and strains. Several prediction models related to the mean stress/strain effect were employed to correlate the experimental results with reference fatigue data for smooth specimens. It is found that Fatemi-Socie model gives good prediction for the present research with the assistance of finite element method. The stress behavior in this deflection-controlled tests is discussed in this study, and the failure surfaces are also examined after tests.

Yip, M.C.; Jen, Y.M. [National Tsing Hua Univ., Hsinchu (Taiwan, Province of China). Dept. of Power Mechanical Engineering

1997-01-01

90

Biaxial seismic behaviour of reinforced concrete columns  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present work focuses on the assessment of the structural response of RC columns under bidirectional horizontal loads in three main streamlines. First, an experimental testing campaign was performed on rectangular columns, for different types of loading. Subsequently, the tested columns were simulated with different non-linear modelling strategies. Finally, a simplified hysteretic model is proposed for the representation of the non-linear response of RC members subjected to biaxial bending

Rodrigeus, Hugo; Humberto, Varum; Anto?nio, Are?de

2013-01-01

91

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

92

Macroscopic behaviour of a biaxial mixture of uniaxial nematics versus hydrodynamics of a biaxial nematic liquid crystal  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We discuss to what extent it is possible to distinguish macroscopically a truly biaxial nematic liquid crystal from a biaxial mixture of uniaxial aggregates in lyotropic systems. We propose for some cases simple experiments to resolve this question. The behaviour in an external magnetic field and the flow alignment in a shear flow experiment is discussed. We find that for small shear the flow alignment angle varies linearly with the shear rate S whereas for truly biaxial nematics it is indepe...

Pleiner, H.; Brand, H. R.

1985-01-01

93

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

94

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

Science.gov (United States)

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

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

2013-12-01

95

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

Science.gov (United States)

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

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

2014-04-01

96

Stretchable graphene: a close look at fundamental parameters through biaxial straining.  

Science.gov (United States)

Tunable biaxial stresses, both tensile and compressive, are applied to a single layer graphene by utilizing piezoelectric actuators. The Gruneisen parameters for the phonons responsible for the D, G, 2D and 2D' peaks are studied. The results show that the D peak is composed of two peaks, unambiguously revealing that the 2D peak frequency (omega(2D)) is not exactly twice that of the D peak (omega(D)). This finding is confirmed by varying the biaxial strain of the graphene, from which we observe that the shift of omega(2D)/2 and omega(D) are different. The employed technique allows a detailed study of the interplay between the graphene geometrical structures and its electronic properties. PMID:20695450

Ding, Fei; Ji, Hengxing; Chen, Yonghai; Herklotz, Andreas; Dörr, Kathrin; Mei, Yongfeng; Rastelli, Armando; Schmidt, Oliver G

2010-09-01

97

Effect of biaxial strain on the band gap of wurtzite Al x Ga1- x N  

Science.gov (United States)

First-principles calculations are applied to investigate the effect of biaxial strain on the band gap of wurtzite Al x Ga1- x N. The band gap and band gap bowing parameter increase with compressive strain and decrease with tensile strain. The strain-induced changes in the band gap of Al x Ga1- x N are linear in the strain range of about -1% to 1% while the linearity is invalid out of the range. The linear coefficient B( x), characterizing the relationship between the band gap and the biaxial stress, with a quadratic form is obtained. The value of the band gap bowing parameter decreases from 1.0 eV for -2% strain to 0.91 eV for unstrained and to 0.67 eV for 2% strain.

Liou, Bo-Ting; Kuo, Yen-Kuang

2012-03-01

98

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

Energy Technology Data Exchange (ETDEWEB)

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.

Hecker, S.S.

1976-01-01

99

Biaxial wheel/hub test facility. Proceedings  

Energy Technology Data Exchange (ETDEWEB)

This User Meeting 'Biaxial Wheel/Hub Test Facility' is held since 1993 and became already a tradition for all engineers, working on the field of design, testing and calculation of wheels and adjacent components. The main goal of the meeting is to exchange the experience in an efficient and reliable validation of the wheel hub assembly and to discuss new improvements or requirements. Therefore, two sections were prepared, which by twelve contributions deals with the experimental approval and numerical analysis. (1) The development of the Biaxial Wheel Test Rig was started before 1980 caused by the shortcomings of the existing simplified test rigs. On the prototype, shown on Fig. 1, different parameters like drum diameter, shape of side rings, tilt angle etc., were investigated and optimized. (2) Not only the test rig itself but also the software as generic load files is of great importance in order to duplicate the customer usage conditions in an accelerated test program. (orig.)

Fischer, G.; Grubisic, V. (eds.)

2001-07-01

100

Dopant Diffusion under Pressure and Stress  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Aziz, Michael

2003-01-01

 
 
 
 
101

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

102

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

103

Reflection of electromagnetic waves at a biaxial-isotropic interface  

Science.gov (United States)

The reflection of electromagnetic waves at a plane boundary between isotropic and biaxial media has been investigated using the kDB approach. The general case has been considered in which the principal dielectric axes of the biaxial medium are oriented at an arbitrary angle to the normal of the plane boundary. In general, two characteristic waves propagate in the biaxial medium, leading to coupling of vertical and horizontal polarizations in the reflected waves. Some special cases are illustrated. The results have applications to problems in remote sensing and integrated optics.

Njoku, E. G.

1983-01-01

104

Biaxially Oriented CdSe Nanorod  

DEFF Research Database (Denmark)

The shape, structure, and orientation of rubbing-aligned cadmium selenide (CdSe) nanorods on polymer coated glass substrates have been studied using transmission electron microscopy (TEM) and grazing incidence X-ray scattering combined with computer simulations. The nanorods are found to be of wurtzite structure and highly monodisperse, and have an essentially ellipsoidal shape with short axes of 8 nm and long axis of 22 nm. The nanorods exhibit preferred biaxial orientation with the hexagonal aâ??c-plane parallel to the sample surface and the c-axis oriented along the rubbing direction of the sample. Some tendency of smectic-A ordering is observed. A quantitative model incorporating atomic structure, rod shape, and preferred orientation was developed for numerically simulating the diffraction peak positions, widths, and intensities, giving good correlation with the experimental observations.

Breiby, Dag W.; Chin, Patrick T.K.

2009-01-01

105

A model for the biaxial post-yield behavior of extruded powder aluminum at elevated temperature  

Energy Technology Data Exchange (ETDEWEB)

A model has been developed which describes the post-yield behavior of extruded powder aluminum tested biaxially in tension and torsion at elevated temperature. Plots of shear stress versus shear strain for the powder aluminum loaded in simple torsion show that the shear stress increases linearly to the yield point, then remains relatively constant in a pure plastic type of behavior. For the tension-torsion tests, there is an initial linear region up to the yield point followed by a fairly linear decrease in shear stress. A similar linear decrease in axial stress with increasing axial strain is observed in uniaxial tension tests. The model for post-yield behavior of extruded powder aluminum gives a quantified description of the macroscopic material behavior in terms of changes in the laminar powder aluminum structure.

Woods, T.O.; Berghaus, D.G. (Georgia Inst. of Tech., Atlanta, GA (United States)); Peacock, H.B. (Westinghouse Savannah River Co., Aiken, SC (United States))

1990-01-01

106

A model for the biaxial post-yield behavior of extruded powder aluminum at elevated temperature  

Energy Technology Data Exchange (ETDEWEB)

A model has been developed which describes the post-yield behavior of extruded powder aluminum tested biaxially in tension and torsion at elevated temperature. Plots of shear stress versus shear strain for the powder aluminum loaded in simple torsion show that the shear stress increases linearly to the yield point, then remains relatively constant in a pure plastic type of behavior. For the tension-torsion tests, there is an initial linear region up to the yield point followed by a fairly linear decrease in shear stress. A similar linear decrease in axial stress with increasing axial strain is observed in uniaxial tension tests. The model for post-yield behavior of extruded powder aluminum gives a quantified description of the macroscopic material behavior in terms of changes in the laminar powder aluminum structure.

Woods, T.O.; Berghaus, D.G. [Georgia Inst. of Tech., Atlanta, GA (United States); Peacock, H.B. [Westinghouse Savannah River Co., Aiken, SC (United States)

1990-12-31

107

Instability of a square sheet under symmetric biaxial loading  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An early experiment found that a square rubber sheet under symmetric biaxial loading may not remain square. This curious result has been one of the most instructive examples in finite elasticity. Here thermodynamic considerations are used to analyze this instability.

Wladimir Augusto das Neves; Liu I-Shih

2000-01-01

108

Characteristics of cyclic crack resistance of aluminium alloys at combined modes of biaxial loading  

Energy Technology Data Exchange (ETDEWEB)

A complex quantative assessment of the effect of the stressed state type and of the angle of the initial crack orientation on the rate of its extension has been conducted for eight aluminium alloys AMr6, O1420T, 1163AT, D16YAT, 1163ATVMO, O1419, 1201AT, and V95AT1 at combined biaxial tension modes. A new dimensionless parameter of cyclic crack resistance has been introduced and substantiated. The existence of a common dependence of the crack growth rate on the proposed parameter for all studied aluminium alloys with different mechanical properties has been established. 15 refs.

Shlyannikov, V.N. [Kazanskij Fiziko-Tekhnicheskij Inst KNTs RAN, Kazan` (Russian Federation)

1994-03-01

109

Deformation modes of nanostructured thin film under controlled biaxial deformation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2013-01-01

110

52Cr Spinor Condensate: A Biaxial or Uniaxial Spin Nematic  

International Nuclear Information System (INIS)

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

2006-05-19

111

Stress state in perforated plates  

International Nuclear Information System (INIS)

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

1977-01-01

112

Bake hardening of hot rolled multiphase steels under biaxial pre-strained conditions  

Energy Technology Data Exchange (ETDEWEB)

Multiphase steels show a strong bake hardening effect being of importance for shaping of car body structural parts. The raised yield strength is exploited for improved crash resistance. Especially the automotive industry has a growing interest in using this effect. Normally the bake hardening effect is examined in tensile tests whereas under industrial conditions shaping of structural parts shows a wide spread of stress strain behaviour, from uniaxial conditions over plain strain to biaxial ones. So it is obvious that the bake hardening behaviour of a material cannot be described with results of the uniaxial tension test only. To give a first answer to this question, the dependence of the bake hardening effect on different biaxial prestrains was investigated for several hot rolled multiphase steels using various baking temperatures and holding times whereas the bake hardening effect under uniaxial prestrain had already been examined in [5]. Considering the choices to generate biaxial strain, a Marciniak forming tool with a diameter of 250 mm mounted on a 2500 kN hydraulic press was chosen. For control of plastic deformation and adjustment the non-contact measuring system ARGUS, was used. To reduce the quantity of experiments ''design of experiments'' and statistical methods were applied for a martensitic steel, a dual phase steel, a complex phase steel, a ferrite-bainite steel, and a retained austenite steel known as TRIP, all in hot rolled condition. As a result, a formula for yield stress, tensile strength and residual deformability was developed. Furthermore, a method was found to predict easily whether a steel under investigation is qualified for additional experiments in regard to bake hardening or more exactly its response to different baking temperatures and holding times. (orig.)

Palkowski, H.; Anke, T. [Inst. fuer Metallurgie, Werkstoffumformung, Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany)

2006-09-15

113

Biaxial alignment in sputter deposited thin films  

Energy Technology Data Exchange (ETDEWEB)

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

Mahieu, S. [Ghent University, Department of Solid State Sciences, Krijgslaan 281/S1 9000 Ghent (Belgium)]. E-mail: stijn.mahieu@ugent.be; Ghekiere, P. [Ghent University, Department of Solid State Sciences, Krijgslaan 281/S1 9000 Ghent (Belgium); Depla, D. [Ghent University, Department of Solid State Sciences, Krijgslaan 281/S1 9000 Ghent (Belgium); Gryse, R. de [Ghent University, Department of Solid State Sciences, Krijgslaan 281/S1 9000 Ghent (Belgium)

2006-12-05

114

Residual stresses of water-jet peened austenitic stainless steel  

International Nuclear Information System (INIS)

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

2013-07-01

115

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

Science.gov (United States)

Biaxial tensile tests of a commercial pure titanium sheet (JIS ?1) were performed using a servo-controlled multiaxial tube expansion testing machine developed by one of the authors [Kuwabara, T. and Sugawara, F., Multiaxial tube expansion test method for measurement of sheet metal deformation behavior under biaxial tension for a large strain range, Int. J. Plasticity, 45 (2013), 103-118]. Tubular specimens with an inner diameter of 54 mm were fabricated by roller bending and TIG welding the as-received test material with a thickness of 0.5 mm. Several linear stress paths in the first quadrant of the stress space were applied to the tubular specimens to measure the contours of plastic work and the directions of the plastic strain rates for an equivalent plastic strain range of 0.05 ? ?0p ? 0.30. It was found that the shapes of the work contours significantly changed with an increase in ?0p and that the Yld2000-2d yield function could reproduce the differential work hardening behavior of the test material by changing the material parameters and the exponent as functions of ?0p.

Sumita, Takeshi; Kuwabara, Toshihiko

2013-12-01

116

Analysis of inclined crack extension in orthotropic solids under biaxial loading  

International Nuclear Information System (INIS)

The objective of this work is to develop the capability to analyze accurately the mixed-mode propagation of a crack in composite structures with elastic orthotropic material stiffness properties and anisotropic material strength characteristics. In order to develop the capability to fully analyze fracture growth and failure in anisotropic structures, we examined the fundamental problem of mixed mode fracture by carrying out the analysis on orthotropic materials with an inclined crack subject to biaxial loading. Our goal here is to include an additional term in the asymptotic expansion of the crack tip stress field and to show that the direction of crack initiation can be significantly affected by that term. We employ the normal stress ratio theory to predict the direction of crack extension. It is shown that the angle of crack extension can be altered by horizontal loads and the use of second order term in the series expansion is important for the accurate determination of crack growth direction

2002-06-01

117

Biaxial strain in graphene adhered to shallow depressions.  

Science.gov (United States)

Measurements on graphene exfoliated over a substrate prepatterned with shallow depressions demonstrate that graphene does not remain free-standing but instead adheres to the substrate despite the induced biaxial strain. The strain is homogeneous over the depression bottom as determined by Raman measurements. We find higher Raman shifts and Gruneisen parameters of the phonons underlying the G and 2D bands under biaxial strain than previously reported. Interference modeling is used to determine the vertical position of the graphene and to calculate the optimum dielectric substrate stack for maximum Raman signal. PMID:19928908

Metzger, Constanze; Rémi, Sebastian; Liu, Mengkun; Kusminskiy, Silvia V; Castro Neto, Antonio H; Swan, Anna K; Goldberg, Bennett B

2010-01-01

118

A shear stabilized biaxial texture in a lamellar block copolymer  

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-12-31

119

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

Science.gov (United States)

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

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

2014-05-01

120

Differential passive and active biaxial mechanical behaviors of muscular and elastic arteries: basilar versus common carotid.  

Science.gov (United States)

Cerebrovascular disease continues to be responsible for significant morbidity and mortality. There is, therefore, a pressing need to understand better the biomechanics of both intracranial arteries and the extracranial arteries that feed these vessels. We used a validated four-fiber family constitutive relation to model passive biaxial stress-stretch behaviors of basilar and common carotid arteries and we developed a new relation to model their active biaxial responses. These data and constitutive relations allow the first full comparison of circumferential and axial biomechanical behaviors between a muscular (basilar) and an elastic (carotid) artery from the same species. Our active model describes the responses by both types of vessels to four doses of the vasoconstrictor endothelin-1 (10(-10)M, 10(-9)M, 10(-8)M, and 10(-7)M) and predicts levels of smooth muscle cell activation associated with basal tone under specific in vitro testing conditions. These results advance our understanding of the biomechanics of intracranial and extracranial arteries, which is needed to understand better their differential responses to similar perturbations in hemodynamic loading. PMID:21599100

Wagner, H P; Humphrey, J D

2011-05-01

 
 
 
 
121

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

122

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. PMID:22236530

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

2012-03-15

123

Effect of strain on deformation in biaxial expension of zirconium  

International Nuclear Information System (INIS)

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

124

Soft elasticity in biaxial smectic and smectic-C elastomers  

CERN Document Server

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

Stenull, O; Stenull, Olaf

2006-01-01

125

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

126

Instability of a square sheet under symmetric biaxial loading  

Directory of Open Access Journals (Sweden)

Full Text Available An early experiment found that a square rubber sheet under symmetric biaxial loading may not remain square. This curious result has been one of the most instructive examples in finite elasticity. Here thermodynamic considerations are used to analyze this instability.

Wladimir Augusto das Neves

2000-01-01

127

Instability of a square sheet under symmetric biaxial loading  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english An early experiment found that a square rubber sheet under symmetric biaxial loading may not remain square. This curious result has been one of the most instructive examples in finite elasticity. Here thermodynamic considerations are used to analyze this instability. [...

Wladimir Augusto das, Neves; Liu, I-Shih.

128

A normalisation procedure for biaxial bias extension tests  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2008-01-01

129

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

2010-03-01

130

Biaxial testing of canine annulus fibrosus tissue under changing salt concentrations  

Scientific Electronic Library Online (English)

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

Huyghe, Jacques M..

131

A structural constitutive model for chemically treated planar tissues under biaxial loading  

Science.gov (United States)

Chemically treated, biologically derived soft collagenous tissues are used extensively in medical devices. To enable prosthesis design through computational methods, physically realistic constitutive models are required. In the present study, a structural approach was utilized that incorporated experimentally measured angular distribution of collagen fibers. Using biaxial mechanical data from our previous study (Annals of Biomedical Engineering, vol. 26(5), pp. 892-902, 1998), the effective fiber and matrix stress-strain responses were predicted. The agreement with the experimental data supported the assumption that the mechanical effects of chemical treatment are equivalent to the addition of an isotropic elastic matrix. An important utility of this model is its ability to separate the effects of chemical treatment on the fibers and matrix. Applications of this approach include utilization in the design of novel chemical treatments that produce specific mechanical responses, the study of fatigue damage, and finite element implementation for tissue engineering scaffold design.

Sacks, Michael S.

132

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

Science.gov (United States)

We report on a systematic study of the stress transferred from an electromechanical piezo-stack into GaAs wafers under a wide variety of experimental conditions. We show that the strains in the semiconductor lattice, which were monitored in situ by means of X-ray diffraction, are strongly dependent on both the wafer thickness and on the selection of the glue which is used to bond the wafer to the piezoelectric actuator. We have identified an optimal set of parameters that reproducibly transfers the largest distortions at room temperature. We have studied strains produced not only by the frequently used uniaxial piezostressors but also by the biaxial ones which replicate the routinely performed experiments using substrate-induced strains but with the advantage of a continuously tunable lattice distortion. The time evolution of the strain response and the sample tilting and/or bending are also analyzed and discussed.

Butkovi?ová, D.; Marti, X.; Saidl, V.; Schmoranzerová-Rozkotová, E.; Wadley, P.; Holý, V.; N?mec, P.

2013-10-01

133

Biaxial fatigue properties of thin-walled composite tubes  

Science.gov (United States)

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

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

1984-01-01

134

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-12-31

135

Biaxial Tensile Testing and Constitutive Modeling of Human Supraspinatus Tendon  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The heterogeneous composition, collagen fiber organization and mechanical properties of the supraspinatus tendon (SST) offer an opportunity for studying the structure-function relationships of fibrous musculoskeletal connective tissues. The objective of this study was to evaluate the contribution of collagen fiber organization to the planar tensile mechanics of the human SST. This was accomplished by fitting biaxial tensile data with a structural constitutive model that incorporates a sample-...

Szczesny, S. E.; Peloquin, J. M.; Cortes, D. H.; Kadlowec, J.; Soslowsky, L. J.; Elliott, D. M.

2012-01-01

136

Mechanic and electromechanic effects in biaxially stretched liquid crystal elastomers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2013-01-01

137

Hypoelastic Soft Tissues: Part II: In-Plane Biaxial Experiments  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In Part I, a novel hypoelastic framework for soft-tissues was presented. One of the hallmarks of this new theory is that the well-known exponential behavior of soft-tissues arises consistently and spontaneously from the integration of a rate based formulation. In Part II, we examine the application of this framework to the problem of biaxial kinematics, which are common in experimental soft-tissue characterization. We confine our attention to an isotropic formulation in order to highlight the...

Freed, Alan D.; Einstein, Daniel R.; Sacks, Michael S.

2010-01-01

138

Modelization of ratcheting in biaxial experiments  

International Nuclear Information System (INIS)

A new unified viscoplastic constitutive equation has been developed in order to interpret ratcheting experiments on mechanical structures of fast reactors. The model is based essentially on a generalized Armstrong Frederick equation for the kinematic variable; the coefficients of the dynamic recovery term in this equation is a function of both instantaneous and accumulated inelastic strain which is allowed to vary in an appropriate manner in order to reproduce the experimental ratcheting rate. The validity of the model is verified by comparing predictions with experimental results for austenitic stainless steel (17-12 SPH) tubular specimens subjected to cyclic torsional loading under constant tensile stress at 600"0C

1989-01-01

139

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Shimizu I.; Tada N.

2010-01-01

140

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

Energy Technology Data Exchange (ETDEWEB)

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

Dake, Yi [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Sridhar, Idapalapati, E-mail: msridhar@ntu.edu.sg [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Xiao Zhongmin [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Kumar, Shashi Bhushan [Det Norske Veritas Pte Ltd, 10 Science Park Drive, Singapore 118224 (Singapore)

2012-04-15

 
 
 
 
141

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

International Nuclear Information System (INIS)

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

1978-01-01

142

Biaxial strain effects on the electronic band structure of wurtzite InxGa1-xN alloys using first-principles calculations  

Science.gov (United States)

Numerical simulation based on first-principles calculations is applied to study the energy band structural characteristics and the band-gap properties of wurtzite InGaN. The results show that the direct band gap, the band gap bowing parameter, the width of valence band, and the width of top valence band increase with compressive strain and decrease with tensile strain. The biaxial strain effect on the indirect band gap is little. In general, there is a larger band gap bowing parameter and larger strain-induced band gap bowing variation in Ga-rich alloys. In addition, the direct band gap, the indirect band gap, the width of valence band, and the width of top valence band decrease with increase of indium composition. Wurtzite InGaN remains the characteristic of a direct band gap material under biaxial stress.

Liou, Bo-Ting; Wu, Bang-Yenn; Kuo, Yen-Kuang

2012-02-01

143

Effect of biaxial strain on the band gap of wurtzite Al{sub x}Ga{sub 1-x}N  

Energy Technology Data Exchange (ETDEWEB)

First-principles calculations are applied to investigate the effect of biaxial strain on the band gap of wurtzite Al{sub x}Ga{sub 1-x} N. The band gap and band gap bowing parameter increase with compressive strain and decrease with tensile strain. The strain-induced changes in the band gap of Al{sub x}Ga{sub 1-x} N are linear in the strain range of about -1% to 1% while the linearity is invalid out of the range. The linear coefficient B(x), characterizing the relationship between the band gap and the biaxial stress, with a quadratic form is obtained. The value of the band gap bowing parameter decreases from 1.0 eV for -2% strain to 0.91 eV for unstrained and to 0.67 eV for 2% strain. (orig.)

Liou, Bo-Ting [Hsiuping University of Science and Technology, Department of Mechanical Engineering, Taichung (China); Kuo, Yen-Kuang [National Changhua University of Education, Department of Physics, Changhua (China)

2012-03-15

144

Effect of crack depth and biaxial loading on the fracture toughness of 15Kh2MFA steel. Evaluation of the 1st series of experiments on cross-shaped and other samples  

International Nuclear Information System (INIS)

Numerical analysis indicated that the fracture toughness of specimens with shallow cracks was 53% to 93% higher than that of specimens with deep cracks and that the fracture toughness of specimens with shallow cracks subjected to a biaxial stress was 18% to 26% lower than that of similar specimens subjected to uniaxial stress. The results of the experiments were also compared to those performed on rotating disks or on standard test specimens. (author)

1997-01-01

145

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

146

Hole doped Dirac states in silicene by biaxial tensile strain  

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

Kaloni, T. P.

2013-03-11

147

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

2013-07-01

148

Biaxially symmetric solutions to 4D higher-spin gravity  

CERN Document Server

We review some aspects of biaxially symmetric solutions to Vasiliev's equations in four dimensional spacetime with negative cosmological constant. The solutions, which activate bosonic fields of all spins, are constructed using gauge functions, projectors and deformed oscillators. The deformation parameters, which are formally gauge invariant, are related to generalized electric and magnetic charges in asymptotic weak-field regions. Alternatively, the solutions can be characterized in a dual fashion using zero-form charges which are higher-spin Casimir invariants built from combinations of curvatures and all their derivatives that are constant on shell and well-defined everywhere.

Iazeolla, Carlo

2012-01-01

149

Determination of principal stresses by Barkhausen effect  

International Nuclear Information System (INIS)

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

150

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. PMID:22428362

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

2012-03-01

151

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

Science.gov (United States)

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

Cheng, Ron-Bin; Hsu, Su-Yuen

2012-01-01

152

Elastic-plastic buckling analysis of rectangular plates subjected to biaxial loads  

Energy Technology Data Exchange (ETDEWEB)

In order to calculate the buckling load of a rectangular plate, the analytical approach is used in this study. The plate is assumed to be simply supported on four edges and loaded by uniform stresses along the edges. If the plate is slender, the buckling is elastic. However, if the plate is sturdy, it buckles in the palstic range. Then, the instantaneous moduli in the constitutive equations depend on the external loading. In this study, the elastic and plastic buckling equations are derived for rectangular plates under biaxial loading, and the corresponding interaction curves are presented. The influences of aspect ratios, load ratios and hardening factors on the buckling stresses are investigated for rectangular plates. From the plastic buckling analysis, the optimal combination of loads is given for the buckling strength. (orig.) [German] Um die Beullast einer Rechteckplatte zu berechnen, wird in dieser Arbeit eine analytische Methode angewandt. Die allseits gelenkig gelagerte Platte wird mit Laengsspannungen belastet. Wenn die Platte duenn ist, findet die Beulung im elastischen Bereich statt. Fuer dicke Platten jedoch findet die Beulung im plastischen Bereich statt. Dann haengen die Werkstofftensoren in den Stoffgleichungen von aeusseren Belastungen ab. In dieser Arbeit werden die elastischen und plastischen Stabilitaetsgleichungen fuer die Rechteckplatten unter zwei axialen Belastungen hergeleitet und die Beziehungen zwischen den beiden Belastungen diskutiert. Die Einfluesse von Seitenverhaeltnis, Spannungsverhaeltnis und Werkstoffverfestigung auf die kritische Beullast werden untersucht. Es wird auch gezeigt, dass die plastische Beulberechnung die optimale Kombination von aeusseren Belastungen fuer die Beulfestigkeit ergibt. (orig.)

Betten, J. [RWTH Aachen (Germany); Shin, C.H. [Korean Register of Shipping, Taejon (Korea). Research and Development Center

2000-03-01

153

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

International Nuclear Information System (INIS)

When a mechanical part is subjected to a repeated mechanical stress, it may be damaged after a number of cycles by several cracks initiation and propagation of a main crack. This is the phenomenon of fatigue damage. The thesis deals specifically with possible damage to some components of nuclear plants due to thermal fatigue. Unlike conventional mechanical fatigue damage where a main crack breaks the part, the thermal fatigue damage usually results in the appearance of a surface crack network. Two aspects are discussed in the thesis. The first is the experimental study of fatigue multiple cracking stage also called multi-cracking. Two mechanical test campaigns with multi-cracking detection by digital image correlation were conducted. These campaigns involve uniaxial and equi-biaxial mechanical loads in tension/compression without mean stress. This work allows to monitor and to observe the evolution of different networks of cracks through mechanical solicitations. The second is the numerical simulation of the phenomenon of fatigue damage. Several types of model are used (stochastic, probabilistic, cohesive finite elements). The experimental results have led to identify a multiple crack initiation law in fatigue which is faced with the numerical results. This comparison shows the relevance of the use of an analytical probabilistic model to find statistical results on the density of cracks that can be initiated with thermal and mechanical fatigue loadings. (author)

2012-01-01

154

Stress  

Science.gov (United States)

This project collects resources for studying mental health and stress issues with middle schoolers. Teens and stress Science NetLinks: The Laughing Brain 2: A Good Laugh Dealing with anger Stress-o-meter Look at each of the above sites. Choose one and read the content. Write a one-paragraph summary. Play interactive games and take quizzes. Keep a log of what you do. Tell which site you liked best and why. Watch the following video for positive things teens do to reduce the stress ...

Deaton, Mrs.

2011-06-10

155

PLASTIC DEFORMATION AND FRACTURE OF STEELS UNDER DYNAMIC BIAXIAL LOADING  

Energy Technology Data Exchange (ETDEWEB)

Dynamic equi-biaxial bulging of thin AerMet 100 alloy plates was studied. The plates were deformed using a gas-gun driven flyer plate test set-up at impact velocities between 1.0 and 2.0 km/sec. The results indicate that in addition to biaxial stretching (and thinning) of the plate, internal cavitation (spallation fracture) results from the complex wave interactions within the plate. No outward evidence of damage was observed at the lower velocities, in the range of 1.0-1.2 km/sec. Fine scale cracking of the plates was observed at impact velocity above approximately 1.4 km/sec. Complete specimen fracture, in the form of multiple petals and pie-shaped fragments, was observed at impact velocity above 1.6 km/sec. Hydrodynamic computer code simulations were performed, prior to and in conjunction with the experiments, to aid in experiment design and interpretation of the experimental data.

Syn, C; Moreno, J; Goto, D M; Belak, J; Grady, D

2004-07-08

156

Energy Storage and Dissipation in Random Copolymers during Biaxial Loading  

Science.gov (United States)

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

Cho, Hansohl; Boyce, Mary

2012-02-01

157

Resonant biaxial 7-mm MEMS mirror for omnidirectional scanning  

Science.gov (United States)

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

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

2013-03-01

158

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

Directory of Open Access Journals (Sweden)

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

Zehui Jiang

2012-11-01

159

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

160

Characteristics of Plane Wave Propagation in Biaxially Anisotropic Gyrotropic Media  

International Nuclear Information System (INIS)

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

2012-03-01

 
 
 
 
161

Failure Locus of 3D Four-Directional Braided Composites Under Biaxial Loading  

Science.gov (United States)

The failure locus of 3D braided four-directional composites under complex loadings, such as tension-shear, compression-shear and tension-tension, can be obtained by micromechanical computation model. A finite element model of representative volume cell (RVC) of the braided composites, explicitly taking into account the braid yarn and matrix, is chosen to analyze the mechanical response. The failure mechanisms of the braided composites observed in experiment can be reproduced by the numerical computation in which the mesoscopic damage models of the braid yarn and matrix are developed. Several failure points of the braided composites under the biaxial loadings can be obtained when different stress ratios are imposed upon the RVC. In comparison with the Tsai-Wu and Tsai-Hahn criteria, the numerical failure loci of the braided composites except the tension-tension results are in good agreement with those results. It can be pointed out that the failure loci of the braided composites can be obtained by the numerical fitting of a large number of the failure points which are calculated by the numerical model.

Wang, Baolai; Fang, Guodong; Liang, Jun; Wang, Zhenqing

2012-06-01

162

Experimental Investigation of the Strain Rate Dependent Behaviour of 2D Biaxially and Triaxially Reinforced Braided Composites  

Science.gov (United States)

The performance of 2D biaxially and triaxially reinforced braided carbon fibre composites under dynamic loading is evaluated in the presented study. The accurate manufacturing of tensile specimen made of braided sleeves is explained particularly with regard to efficiency and reproducibility. In order to determine reliable strain rate dependent properties, the high-speed testing procedure is discussed. Using five materials, the parameter identification is described and relevant material data is provided. The measured stiffnesses and strengths are used to predict the non-linear stress-strain behaviour with an earlier proposed phenomenological damage model for textile composites. The gained orthotropic property-profile provides the input parameters for a numerical analysis of braided composite components using the calibrated model.

Böhm, R.; Hornig, A.; Luft, J.; Becker, M.; Koch, I.; Grüber, B.; Hufenbach, W.

2013-08-01

163

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

Science.gov (United States)

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

Abe, T.; Takarada, W.; Kikutani, T.

2014-05-01

164

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

DEFF Research Database (Denmark)

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

Larsen, Arne Nylandsted; Zangenberg, Nikolaj

2005-01-01

165

Superplastic deformation of an Al-Li-Cu-Zr alloy under uniaxial and biaxial tension  

International Nuclear Information System (INIS)

This paper reports that the superplasticity of an Al-Li-Cu-Zr alloy has been studied under uniaxial tension and biaxial bulging conditions using hydrostatic pressure. An optimum tensile elongation of 850% at a strain rate of 3/10-4/sec was obtained at 758 K. The maximum true thickness stain was 1.22 for a biaxially deformed specimen under the same conditions. It was shown that strain rate dependent flow hardening was related to necking refile. It was observed that cavity growth during superplastic deformation depended on the type of loading. Under biaxial bulging conditions, the cavities grew by forming cavity fissure networks along the grain boundaries. It was found that, by the superimposition of hydrostatic pressure, cavitation was retarded and the superplastic ductility was increased in both tensile and biaxial deformation

1990-04-16

166

Frequency doubling with laser beams transformed by conical refraction in a biaxial crystal  

International Nuclear Information System (INIS)

The second-harmonic generation with laser beams transformed by internal conical refraction in a biaxial crystal was studied in a cascaded two-crystal arrangement, where the biaxial crystal transformed the input Gaussian beam and another nonlinear crystal was used for frequency doubling of the produced conical refraction pattern. Several specific second-harmonic beam profiles obtained for various positions of the nonlinear crystal along the beam propagation direction are considered and discussed

2011-05-01

167

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

International Nuclear Information System (INIS)

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

2011-07-19

168

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

Science.gov (United States)

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

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

2014-07-01

169

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2011-01-01

170

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

International Nuclear Information System (INIS)

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

2006-04-01

171

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

Energy Technology Data Exchange (ETDEWEB)

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

Abdalla, Hany F., E-mail: hany_f@aucegypt.ed [Mechanical Engineering Department, American University in Cairo (Egypt); Megahed, Mohammad M., E-mail: mmegahed47@yahoo.co [Dept. of Mechanical Design and Production, Faculty of Engineering, Cairo University (Egypt); Younan, Maher Y.A., E-mail: myounan@aucegypt.ed [Mechanical Engineering Department, American University in Cairo (Egypt)

2011-03-15

172

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

International Nuclear Information System (INIS)

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

2011-03-01

173

Biaxial mechanical properties of muscle-derived cell seeded small intestinal submucosa for bladder wall reconstitution.  

Science.gov (United States)

Bladder wall replacement remains a challenging problem for urological surgery due to leakage, infection, stone formation, and extensive time needed for tissue regeneration. To explore the feasibility of producing a more functional biomaterial for bladder reconstitution, we incorporated muscle-derived cells (MDC) into small intestinal submucosa (SIS) scaffolds. MDC were harvested from mice hindleg muscle, transfected with a plasmid encoding for beta-galactosidase, and placed into single-layer SIS cell culture inserts. Twenty-five MDC and/or SIS specimens were incubated at 37 degrees C for either 10 or 20 days. After harvesting, mechanical properties were characterized using biaxial testing, and the areal strain under 1 MPa peak stress used to quantify tissue compliance. Histological results indicated that MDC migrated throughout the SIS after 20 days. The mean (+/-SE) areal strain of the 0 day control group was 0.182 +/- 0.027 (n=5). After 10 days incubation, the mean (+/-SE) areal strain in MDC/SIS was 0.247 +/- 0.014 (n=5) compared to 10 day control SIS 0.200 +/- 0.024 (n=6). After 20 days incubation, the mean areal strain of MDC/SIS was 0.255 +/- 0.019 (n=5) compared to control SIS 0.170 +/- 0.025 (n=5). Both 10 and 20 days seeded groups were significantly different (p=0.027) than that of incubated SIS alone, but were not different from each other. These results suggest that MDC growth was supported by SIS and that initial remodeling of the SIS ECM had occurred within the first 10 days of incubation, but may have slowed once the MDC had grown to confluence within the SIS. PMID:15275818

Lu, Shing-Hwa; Sacks, Michael S; Chung, Steve Y; Gloeckner, D Claire; Pruchnic, Ryan; Huard, Johnny; de Groat, William C; Chancellor, Michael B

2005-02-01

174

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2005-01-01

175

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

International Nuclear Information System (INIS)

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

2006-05-15

176

Deuterium NMR investigation of the biaxial nematic phase in an organosiloxane tetrapode.  

Science.gov (United States)

Deuterium NMR is used to examine the molecular order exhibited by an organosiloxane tetrapode giving the first experimental evidence, using a bulk sample, for the existence of a biaxial nematic phase in this type of compounds. The temperature dependence of the averaged quadrupolar coupling constant and asymmetry parameter was determined in the compound's nematic phase. Two distinct regimes could be identified, one with a vanishing asymmetry parameter corresponding to a uniaxial nematic phase and another with a significant temperature dependent asymmetry parameter, corresponding to a biaxial nematic phase. The high values obtained for the asymmetry parameter at the lower end of the nematic range are well above experimental error and constitute a definite proof of the biaxial nature of the nematic phase exhibited by the studied compound for those temperatures. PMID:15783524

Figueirinhas, J L; Cruz, C; Filip, D; Feio, G; Ribeiro, A C; Frère, Y; Meyer, T; Mehl, G H

2005-03-18

177

The mechanical behavior of extruded powder aluminum subjected to biaxial loadings at elevated temperature  

Energy Technology Data Exchange (ETDEWEB)

The goal of this investigation is to develop a description of the biaxial behavior of extruded powder aluminum at elevated temperature. Specimens made of extruded 101 ALCOA (Aluminum Company of America) powder aluminum and specimens made from 1100 commercial aluminum rod are tested biaxially in tension-torsion and compression-torsion loadings at the extrusion temperature. The powder aluminum is examined microscopically and stereological methods are used to give a quantified description of the material behavior in terms of changes in the laminar powder material structure. A model for the biaxial (tension-torsion) behavior of extruded powder aluminum is developed. This description is consistent with a previous analysis of behavior in pure tension.

Woods, T.O.; Berghaus, D.G. [Georgia Inst. of Tech., Atlanta, GA (United States); Peacock, H.B. [Westinghouse Savannah River Co., Aiken, SC (United States)

1990-12-31

178

The mechanical behavior of extruded powder aluminum subjected to biaxial loadings at elevated temperature  

Energy Technology Data Exchange (ETDEWEB)

The goal of this investigation is to develop a description of the biaxial behavior of extruded powder aluminum at elevated temperature. Specimens made of extruded 101 ALCOA (Aluminum Company of America) powder aluminum and specimens made from 1100 commercial aluminum rod are tested biaxially in tension-torsion and compression-torsion loadings at the extrusion temperature. The powder aluminum is examined microscopically and stereological methods are used to give a quantified description of the material behavior in terms of changes in the laminar powder material structure. A model for the biaxial (tension-torsion) behavior of extruded powder aluminum is developed. This description is consistent with a previous analysis of behavior in pure tension. (author).

Woods, T.O.; Berghaus, D.G. (Georgia Institute of Technology, Atlanta, Georgia (USA)); Peacock, H.B. (Westinghouse Savannah River Company, Savannah River Laboratory, Aiken, South Carolina (USA))

1990-01-01

179

The mechanical behavior of extruded powder aluminum subjected to biaxial loadings at elevated temperature  

Energy Technology Data Exchange (ETDEWEB)

The goal of this investigation is to develop a description of the biaxial behavior of extruded powder aluminum at elevated temperature. Specimens made of extruded 101 ALCOA (Aluminum Company of America) powder aluminum and specimens made from 1100 commercial aluminum rod are tested biaxially in tension-torsion and compression-torsion loadings at the extrusion temperature. The powder aluminum is examined microscopically and stereological methods are used to give a quantified description of the material behavior in terms of changes in the laminar powder material structure. A model for the biaxial (tension-torsion) behavior of extruded powder aluminum is developed. This description is consistent with a previous analysis of behavior in pure tension.

Woods, T.O.; Berghaus, D.G. (Georgia Inst. of Tech., Atlanta, GA (United States)); Peacock, H.B. (Westinghouse Savannah River Co., Aiken, SC (United States))

1990-01-01

180

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

CERN Document Server

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

 
 
 
 
181

Phase Shift of Polarized Light after Transmission through a Biaxial Anisotropic Thin Film  

International Nuclear Information System (INIS)

Based on the theoretical analysis of biaxial birefringent thin films with characteristic matrix method, we investigate the phase shift on transmission of a tilted columnar biaxial film at normal and oblique incidence over 300–1200 nm for s- and p-polarized waves. Compared with the simplified calculation method, the interference effects of the birefringent thin film are considered to yield more accurate results. The quarter wavelength phase shift calculated with the characteristic matrix method is consistent with that monitored with in situ measurement by two-angle ellipsometry, which validates our complied program for the calculation of the phase shift of the biaxial anisotropic thin film. Furthermore, the characteristic matrix method can be easily used to obtain continuous adjustable phase retardation at oblique incidence, whereas the simplified calculation method is valid for the case of normal incidence. A greater generality and superiority of the characteristic matrix method is presented

2013-01-01

182

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

International Nuclear Information System (INIS)

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

2013-01-01

183

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

International Nuclear Information System (INIS)

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

2011-09-02

184

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.

Garima Joshi

2012-11-01

185

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

186

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

Energy Technology Data Exchange (ETDEWEB)

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

Nie, H.-Y. [Surface Science Western, Room G-1, Western Science Centre, University of Western Ontario, London, Ont., N6A 5B7 (Canada)]. E-mail: hnie@uwo.ca; Walzak, M.J. [Surface Science Western, Room G-1, Western Science Centre, University of Western Ontario, London, Ont., N6A 5B7 (Canada); McIntyre, N.S. [Surface Science Western, Room G-1, Western Science Centre, University of Western Ontario, London, Ont., N6A 5B7 (Canada)

2006-12-15

187

Effect of T-stress on dislocation emission in iron  

Energy Technology Data Exchange (ETDEWEB)

We compare continuum predictions for dislocation emission from a crack tip loaded under mode I, biaxial conditions with atomistic results for bcc iron. The simulations validate the continuum prediction that, as the T-stress increases, so does the threshold for dislocation nucleation; hence, the propensity for brittle response increases.

Beltz, Glenn E.; Machova, Anna

2004-02-15

188

Effect of T-stress on dislocation emission in iron  

International Nuclear Information System (INIS)

We compare continuum predictions for dislocation emission from a crack tip loaded under mode I, biaxial conditions with atomistic results for bcc iron. The simulations validate the continuum prediction that, as the T-stress increases, so does the threshold for dislocation nucleation; hence, the propensity for brittle response increases

2004-02-01

189

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

International Nuclear Information System (INIS)

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

2010-01-01

190

MEANING OF THE BIAXIAL FLEXURE TESTS OF DISCS FOR STRENGTH MEASUREMENTS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The biaxial flexure of discs is a test widely performed for the strength rneasurement of ceramics. However its use requires some care and it leads to results strongly dependent on the experimental conditions. Some of the main parameters of this test are emphasized on the basis of strain gage measurements and tests performed on silica soda lime glass.

1986-01-01

191

Biaxial nematic order and phase behavior studies in an organosiloxane tetrapode using complementary deuterium NMR experiments.  

Science.gov (United States)

The biaxial nematic phase was recently observed in different thermotropic liquid crystals, namely bent-core compounds, side-chain polymers, bent-core dimers, and organosiloxane tetrapodes. In this work, a series of experiments with a nematic organosiloxane tetrapode where nuclear magnetic resonance (NMR) spectra are collected while the sample is continuously rotating around an axis perpendicular to the magnetic field, are discussed in conjunction with the analysis of a deuterium NMR experiment on the same system reported earlier. The sample used is a mixture of a deuterated probe with the tetrapode. The mixture exhibits a nematic range between -40 degrees C and 37 degrees C. The results of the two independent, but complementary deuterium NMR experiments confirm the existence of a biaxial nematic phase for temperatures below 0 degrees C with high values of the asymmetry parameter at low temperatures. The presence of slow movements of the tetrapode mesogenic units in the low-temperature regime could also be detected through the analysis of the NMR spectra. Simulations indicate that these movements are mainly slow molecular reorientations of the mesogenic units associated with the presence of collective modes in the nematic phases of this compound. In the case of tetrapodes, recent investigations attribute the origin of biaxiality to the hindering of reorientations of the laterally attached mesogenic units which constitute the tetrapode. This study relates the molecular movements with the nematic biaxial ordering of the system. PMID:19113138

Cruz, C; Figueirinhas, J L; Filip, D; Feio, G; Ribeiro, A C; Frère, Y; Meyer, T; Mehl, G H

2008-11-01

192

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

Science.gov (United States)

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

Mackay, Tom G.

2014-01-01

193

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

1994-06-19

194

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

195

The influence of the stress state on Ksub(Ic)  

International Nuclear Information System (INIS)

To get a first impression of the influence of stress states of higher multi-axiality than plane strain on Ksub(c) a specimen has been created, in which a bi-axial nominal stress state arises by uniaxial tension. This is attained by tension superimposed by transverse bending stress. The stress distribution without crack was analysed by photoelasticity as well as by finite element method. The results were identical. The stress distribution in the fracture (crack) plane was somewhat inhomogeneous, of course. But the ratio of the stress parallel to the tension axis to that perpendicular to it was max. 1:0.3 with a mean value 1:0.15. Specimens of this type were machined from a rolled sheet of the steel 22 NiMoCr 37, with specimen thickness of about 50 mm. For comparison single-edge notched specimens of the same cross section were prepared from the same material. Fatigue cracks were made following ASTM Recommendations. The fracture mechanics tests were carried out at a temperature of -1000C. Although valid Ksub(Ic)-values following the rigorous intention of the linear elastic fracture mechanics (ASTM Recommendations) were not obtained, the differences between the results of the two types of specimens and stress states were significant. The Ksub(Q)-values of the bi-axial stressed specimen were about 25% lower than that of the single-edge notched specimen. The deviation of the load-displacement trace from the linear elastic behavior was greater for the single-edge notched specimens than for the bi-axial stressed specimens. The consequences of these results for the assessment of flaws in pressure vessels are evident considering that bi-axial nominal stress states occur in pressure vessels

1977-08-19

196

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.

2008-01-01

197

Detection of phase biaxiality in liquid crystals by use of the quadrupole shift in 131Xe NMR spectra.  

Science.gov (United States)

An experimental method to unambiguously distinguish between uniaxial and biaxial liquid crystal phases is introduced. The method is based on the second order quadrupole shift (SOQS) observable in 131Xe NMR spectra of xenon dissolved in liquid crystals. It is shown that besides revealing the biaxiality, the 131Xe SOQS offers a novel method to determine the tilt angle in smectic C phases. As an example, the 131Xe SOQS in a ferroelectric liquid crystal is reported. It yields up a biaxial phase in between isotropic and smectic C phases. PMID:21231771

Jokisaari, Jukka P; Kantola, Anu M; Lounila, Juhani A; Ingman, L Petri

2011-01-01

198

Influence of the mesogenic shape on the molecular dynamics and phase-biaxiality of liquid crystal main-chain polymers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ever since the first theoretical phase diagram that was published by Straley in 1974, extensive theoretical efforts have been made on predicting the molecular shape and properties of mesogens that can form a biaxial-nematic phase. The theories suggest that mesogens, whose form is board-like rather than rod-like, are more likely to form biaxial phases. In this study we show that the onset of phase-biaxiality for nematic main-chain polymers can indeed, without significantly changing the glass t...

Broemmel, Felicitas; Zou, Peng; Finkelmann, Heino; Hoffmann, Anke

2013-01-01

199

Effect of seed layer on biaxial texturing of pulsed laser deposited YSZ films on electrodeposited Ir/Ni-W tapes  

International Nuclear Information System (INIS)

Pulsed laser deposition (PLD) of biaxially textured Y2O3 stabilized ZrO2 (YSZ) layers on electrodeposited Ir/Ni-W tape is reported. Biaxial texturing is obtained by deposition of an YSZ seed layer at 800 deg. C in 10-6 Torr vacuum. X-ray diffraction (XRD) studies of ?-2? and pole figures confirmed in-plane, out-of-plane biaxial texturing with ?? = 8o and ?? = 7.9o. Atomic force microscopy (AFM) revealed a surface with roughness of about 3 nm

2006-09-01

200

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

International Nuclear Information System (INIS)

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

2012-05-01

 
 
 
 
201

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

International Nuclear Information System (INIS)

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

2009-04-01

202

Fatigue biaxiale à grand nombre de cycles : étude expérimentale et modèle d'endommagement à deux échelles probabiliste  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Les structures industrielles sont soumises à des sollicitations complexes dont certaines biaxiales. Afin d'étudier de manière expérimentale l'influence de la biaxialité du chargement sur la durée de vie, des essais de fatigue biaxiale à grand nombre de cycles sont menés sur matériaux acier inoxydable austénitique 304L CLI, et alliage de titane. Une géométrie d'éprouvette en croix, affinée en son centre a été dimensionnée pour cette étude. Une vingtaine d'essais en efforts im...

2009-01-01

203

Determination technique of beginning of corrosion crack formation under conditions of influence of biaxial tensile stresses  

International Nuclear Information System (INIS)

A cell for investigation of corrosion cracking of high-strength steels under the action of external polarization is developed. It is shown that anode current spike at the application of tensile to the specimen made of high-strength steel is a criterion of corrosion crack formation that can be used during studying of kinetics of corrosion cracking processes

1982-01-01

204

Anisotropic swelling observed during stress-free reirradiation of AISI 304 tubes previously irradiated under stress  

Science.gov (United States)

A 'history effects' experiment was conducted in EBR-II that involved the reirradiation of AISI 304 cladding and capsule tubes. It is shown that when irradiated tubes had not previously experienced stress, subsequent irradiation led to additional swelling strains that were isotropically distributed. However, when tubes previously irradiated under a 2:1 biaxial stress were reirradiated without stress the additional swelling strains were not isotropically distributed. The tubes obviously retained a memory of the previous stress state that appears to be attempting to distribute strains in the directions dictated by the previous stress state. It is clear, however, that the memory of that stress state is fading as the anisotropic dislocation microstructure developed during irradiation under stress is replaced by an isotropic dislocation microstructure during subsequent exposure in the absence of stress. It is also shown that once the transient regime of swelling nears completion, further changes in stress state or irradiation temperature have no influence on the swelling rate thereafter.

Garner, F. A.; Flinn, J. E.; Hall, M. M.

2009-04-01

205

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

206

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

1996-03-10

207

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

Science.gov (United States)

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

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

208

YBCO coated conductor using biaxially textured Ni-0.1%Mn substrate  

International Nuclear Information System (INIS)

A new biaxially textured tape of Ni-0.1%Mn was used as a substrate for YBCO coated conductor through the RABiTS approach. Multi-layer CeO2/YSZ/Y2O3 buffer layers and YBCO film were deposited on the substrate by pulsed laser deposition. The deposition conditions of the buffer layers and the YBCO film were studied and compared. Biaxial textures have been obtained for buffer layers on Ni-0.1%Mn substrates. The YBCO films were deposited at two different deposition rates, corresponding to two different laser repetition rates, 10 and 200 Hz, respectively. The relationship between the J c and the thickness of YBCO film was studied. AFM was used to examine the surface morphology and roughness of the YBCO films. The best J c of YBCO films on these metal substrates was 2.3 x 106 A/cm2 at 77 K, 0 T

2006-02-01

209

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

International Nuclear Information System (INIS)

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

2013-01-01

210

Biaxially aligned buffer layers of cerium oxide, yttria stabilized zirconia, and their bilayers  

Energy Technology Data Exchange (ETDEWEB)

Biaxially aligned cerium oxide (CeO{sub 2}) and yttria stabilized zirconia (YSZ) films were deposited on Ni-based metal (Hastelloy C276) substrates held at room temperature using ion beam assisted (IBAD) magnetron deposition with the ion beam directed at 55{degree} to the normal of the film plane. In addition, we achieved, room-temperature epitaxial growth of CeO{sub 2} by bias sputtering to form biaxially aligned CeO{sub 2}/YSZ bilayers. The crystalline structure and in-plane orientation of films was investigated by x-ray diffraction techniques. Both the IBAD CeO{sub 2} and YSZ films, and the CeO{sub 2}/YSZ bilayers have a (111) pole in the ion beam direction. {copyright} {ital 1997 American Institute of Physics.}

Gnanarajan, S.; Katsaros, A.; Savvides, N. [CSIRO Telecommunications and Industrial Physics, Lindfield NSW 2070 (Australia)

1997-05-01

211

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

CERN Document Server

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

Martelli, Dario

2011-01-01

212

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.

2013-06-01

213

Nucleation of epitaxial yttria-stabilized zirconia on biaxially textured (001) Ni for deposited conductors  

International Nuclear Information System (INIS)

The nucleation of (001)-oriented yttria-stabilized zirconia (YSZ) directly on the (001) Ni surface is realized via nucleation on an oxygen-terminated nickel surface using pulsed-laser deposition. Under conditions where the nickel surface is either oxygen free or substantially covered with NiO, a mixed orientation of YSZ occurs. The epitaxial YSZ layer grown on a biaxially textured Ni(001) surface was used as a single buffer layer for a high temperature superconducting coated conductor architecture, yielding superconducting YBa2Cu3O7 films with high critical current densities, Jc. This architecture eliminates the necessity for a multilayer buffer architecture, since high Jc superconducting films are achieved with no intermediate buffer layer between the (001) YSZ and the biaxially textured metal. (c) 2000 American Institute of Physics

2000-04-24

214

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Rheological and fracture properties of optimally mixed flour doughs from three wheat cultivars which perform differently in cereal products were studied in uniaxial and biaxial extension. Doughs were also tested in small angle sinusoidal oscillation. In accordance with previously published results the linear region was found to be very small. The rheological properties at small deformations hardly depended on the cultivar. A higher water content of the dough resulted in a lower value for the ...

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

2004-01-01

215

Large-deformation properties of wheat dough in uni- and biaxial extension. Part II. Gluten dough  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Glutens were isolated from flour of three European wheat cultivars which perform differently in cereal products. The rheological and fracture properties of gluten-water doughs were determined in uniaxial and biaxial extension at large deformations and small angle sinusoidal oscillation tests and compared with the mechanical properties of the parental flour doughs. At 25 °C the linear region was in the same range as that of flour dough, while at a higher temperature (45 °C) the linear region...

Sliwinski, E. L.; Hoef, M.; Kolster, P.; Vliet, T.

2004-01-01

216

Nonlinear susceptibility and dynamic hysteresis loops of magnetic nanoparticles with biaxial anisotropy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The nonlinear ac susceptibility and dynamic magnetic hysteresis (DMH) of a single domain ferromagnetic particle with biaxial anisotropy subjected to both external ac and dc fields of arbitrary strength and orientation are treated via Brown's continuous diffusions model [W. F. Brown, Jr., Phys. Rev. 130, 1677 (1963)] of magnetization orientations. The DMH loops and nonlinear ac susceptibility strongly depend on the dc and ac field strengths, the polar angle between the easy axis of the pa...

Ouari, Bachir; Titov, Serguey V.; El Mrabti, Halim; Kalmykov, Yuri P.

2013-01-01

217

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

2013-10-01

218

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% 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). PMID:22551761

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

2012-06-13

219

Confocal fluorescence microscope with dual-axis architecture and biaxial postobjective scanning  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a novel confocal microscope that has dual-axis architecture and biaxial postobjective scanning for the collection of fluorescence images from biological specimens. This design uses two low-numerical-aperture lenses to achieve high axial resolution and long working distance, and the scanning mirror located distal to the lenses rotates along the orthogonal axes to produce arc-surface images over a large field of view (FOV). With fiber optic coupling, this microscope can potentially b...

Wang, Thomas D.; Contag, Christopher H.; Mandella, Michael J.; Chan, Ning Y.; Kino, Gordon S.

2004-01-01

220

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

 
 
 
 
221

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Objetivo: O objetivo deste estudo foi avaliar a resistência flexural e o módulo de flexão de dois sistemas adesivos, através de ensaio de resistência flexural biaxial. Metodologia: Os adesivos (Pentron Clinical Technologies) estudados foram: Bond 1 (B1) e NanoBond (NB). Treze discos de cada adesivo foram preparados com dimensões aproximadas de 6,1 mm de diâmetro e 0,6 mm de espessura. Os discos de adesivos foram confeccionados utilizando-se moldes de teflon e fotopolimerizados com apar...

Liberti, Michele Santana Et Al

2009-01-01

222

Biaxial alignment in off-normally deposited films using highly ionized fluxes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The influence of highly ionized fluxes on the biaxial alignment in thin films has been investigated by studying the relation between the effect of ionization degrees and different process conditions, including magnetron position, working pressure and substrate bias voltage. In this thesis work, SEM and XRD techniques were employed to study the morphology and crystallographic properties of Cr films grown by High Power Impulse Magnetron Sputtering (HiPIMS) and Direct Current Magnetron Sputterin...

2013-01-01

223

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

Science.gov (United States)

We use graphene bubbles to study the Raman spectrum of graphene under biaxial (e.g., isotropic) strain. Our Gruneisen parameters are in excellent agreement with the theoretical values. Discrepancy in the previously reported values is attributed to the interaction of graphene with the substrate. Bilayer balloons (intentionally pressurized membranes) have been used to avoid the effect of the substrate and to study the dependence of strain on the interlayer interactions. PMID:22149458

Zabel, Jakob; Nair, Rahul R; Ott, Anna; Georgiou, Thanasis; Geim, Andre K; Novoselov, Kostya S; Casiraghi, Cinzia

2012-02-01

224

TIME DEPENDENT BIAXIAL MECHANICAL BEHAVIOR OF THE AORTIC HEART VALVE LEAFLET  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2007-01-01

225

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 thi [...] s study was to compare the biaxial flexural strength of three core ceramic materials. MATERIAL AND METHODS: Three groups of 10 disc-shaped specimens (16 mm diameter x 1.2 mm thickness - in accordance with ISO-6872, 1995) were made from the following ceramic materials: Turkom-Cera Fused Alumina [(Turkom-Ceramic (M) Sdn Bhd, Puchong, Selangor, Malaysia)], In-Ceram (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany) and Vitadur-N (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany), which were sintered according to the manufacturer's recommendations. The specimens were subjected to biaxial flexural strength test in an universal testing machine at a crosshead speed of 0.5 mm/min. The definitive fracture load was recorded for each specimen and the biaxial flexural strength was calculated from an equation in accordance with ISO-6872. RESULTS: The mean biaxial flexural strength values were: Turkom-Cera: 506.8±87.01 MPa, In-Ceram: 347.4±28.83 MPa and Vitadur-N: 128.7±12.72 MPa. The results were analyzed by the Levene's test and Dunnett's T3 post-hoc test (SPSS software V11.5.0 for Windows, SPSS, Chicago, IL, USA ) at a preset significance level of 5% because of unequal group variances (P

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

226

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 becaus...

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

2013-01-01

227

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2008-01-01

228

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 Correlation technique is used to measure strain during loading and detect crack initiation early. A special optical assembly and a stroboscopic sampling method are set up in this purpose. Several t...

2010-01-01

229

Presentation of the new biaxial wheel test rig at BORBET  

Energy Technology Data Exchange (ETDEWEB)

The test rig offers the following advantages: (a) Simulation of different types of loads in the development phase, such as Eurocycle test cycles, arbitrary test courses, figure eight driving and circular courses. (b) Short testing times: 10 000 km in four days correspond to 300 000 km in normal operations. (c) Realistic deformation of all wheel and hub areas under operational loads. (d) Little material consumption. (e) Performance of stress analyses. (f) Complete replacement of previous test procedures and drive tests. (g) Easy handling and adaptation of the load program. (h) More ecnomic, more reliable, and more environmentally friendly strength test taking into account the safety aspects. (orig./AKF)

Voellmecke, F.J. [BORBET GmbH, Hallenberg-Hesborn (Germany)

2000-07-01

230

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

Science.gov (United States)

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

Liu, Dahai; Yu, Haiping; Li, Chunfeng

2011-03-01

231

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

International Nuclear Information System (INIS)

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

2011-10-01

232

Directional differences in the biaxial material properties of fascia lata and the implications for fascia function.  

Science.gov (United States)

Fascia is a highly organized collagenous tissue that is ubiquitous in the body, but whose function is not well understood. Because fascia has a sheet-like structure attaching to muscles and bones at multiple sites, it is exposed to different states of multi- or biaxial strain. In order to measure how biaxial strain affects fascia material behavior, planar biaxial tests with strain control were performed on longitudinal and transversely oriented samples of goat fascia lata (FL). Cruciform samples were cycled to multiple strain levels while the perpendicular direction was held at a constant strain. Structural differences among FL layers were examined using histology and SEM. Results show that FL stiffness, hysteresis, and strain energy density are greater in the longitudinal vs. transverse direction. Increased stiffness in the longitudinal layer is likely due to its greater thickness and greater average fibril diameter compared to the transverse layer(s). Perpendicular strain did not affect FL material behavior. Differential loading in the longitudinal vs. transverse directions may lead to structural changes, enhancing the ability of the longitudinal FL to transmit force, store energy, or stabilize the limb during locomotion. The relative compliance of the transverse fibers may allow expansion of underlying muscles when they contract. PMID:24647722

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

2014-06-01

233

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

International Nuclear Information System (INIS)

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

1998-01-01

234

Biaxially aligned template films fabricated by inclined-substrate deposition for YBCO-coated conductor applications.  

Energy Technology Data Exchange (ETDEWEB)

Inclined substrate deposition (ISD) has the potential for rapid production of high-quality biaxially textured buffer layers, which are important for YBCO-coated conductor applications. We have grown biaxially textured MgO films by ISD at deposition rates of 20-100 {angstrom}/sec. Columnar grains with a roof-tile surface structure were observed in the ISD-MgO films. X-ray pole figure analysis revealed that the (002) planes of the ISD-MgO films are tilted at an angle from the substrate normal. A small {phi}-scan full-width at half maximum (FWHM) of {approx}9{sup o} was observed on MgO films deposited at an inclination angle of 55{sup o}. In-plane texture in the ISD MgO films developed in the first 0.5 {micro}m from the interface, then stabilized with further increases in film thickness. YBCO films deposited by pulsed laser deposition on ISD-MgO buffered Hastelloy C276 substrates were biaxially aligned with the c-axis parallel to the substrate normal. T{sub c} of 91 K with a sharp transition and transport J{sub c} of 5.5 x 10{sup 5} A/cm{sup 2} at 77 K in self-field were measured on a YBCO film that was 0.46-{micro}m thick, 4-mm wide, 10-mm long.

Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Erck, R. A.; Dorris, S. E.; Miller, D. J.; Balachandran, U.

2002-08-12

235

3D shape identification of parallelepiped flaw by means of biaxial MFLT using neural network  

International Nuclear Information System (INIS)

In this paper, we attempt to evaluate the three-dimensional shape of a parallelepiped flaw and identify its location, i.e. the horizontal position and the located surface, by means of biaxial Magnetic Flux Leakage Testing (MFLT), employing a Neural Network (NN). The specimen is a magnetic material (SS400) subjected to a magnetic field, and the magnetic flux in the specimen leaks near the flaw. We measure the biaxial Magnetic Flux Leakage (MFL), i.e, the tangential and the normal components of the MFL, along a line parallel to the specimen's surface. We then approximate the measured biaxial MFL distributions by means of elementary functions with a small number of coefficients. The approximation coefficients are extracted as Characteristic Quantities (CQs) of the MFL distribution. The horizontal position of the flaw along the measurement line is characterized by some of these CQs. NN is used to infer the cross section of the flaw, i.e, the width, depth, and located surface of the CQs. By repeating a similar process along several measurement lines parallel to the specimen's surface, we can identify the three-dimensional shape of the flaw, including its location. The NN, trained with several known flaws, was found to be able to evaluate the three-dimensional shape and location of a parallelepiped flaw with a high level of accuracy. (author)

2010-03-01

236

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

International Nuclear Information System (INIS)

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

2003-05-15

237

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

Science.gov (United States)

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

Lu, Xiancong; Chen, Lixiang

2012-05-21

238

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

239

Stresses in sulfuric acid anodized coatings on aluminum  

Science.gov (United States)

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

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

1993-01-01

240

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

Science.gov (United States)

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 -150 MPa 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 100 MPa. 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. PMID:23917041

Tung, Patrick K M; Mudie, Stephen; Daniels, John E

2013-12-01

 
 
 
 
241

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

International Nuclear Information System (INIS)

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

1985-01-01

242

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

International Nuclear Information System (INIS)

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

1986-01-01

243

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

244

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

245

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

International Nuclear Information System (INIS)

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

2009-01-01

246

Plasma Surface Functionalization of Biaxially Oriented Polypropylene Films with Trimethyl Borate  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. ...

Nursel Dilsiz; Hande Yavuz; Süleyman Çörekçi; Mehmet Çakmak

2011-01-01

247

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

CERN Document Server

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

Galatola, P

2001-01-01

248

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

International Nuclear Information System (INIS)

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

1983-03-01

249

Biaxiality of Liquid Crystal Formed by Bent-Core Molecules with a Transverse Dipole Moment Deviating from their Angular Bisector  

International Nuclear Information System (INIS)

Monte Carlo simulations are performed to study the phase diagram of liquid crystals formed by bent-core molecules with a strong transverse dipole moment deviating from their angular bisector. The results show that the strong dipolar interaction, after suppressing uniaxial phases, encourages biaxiality, which leads to a Landau point or even to a Landau line in the phase diagram, inducing a more stable biaxial nematic phase. It is also found that a deviation of dipole moment from the angular bisector also suppresses uniaxiality in the small bend-angle regime

2013-10-01

250

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

Energy Technology Data Exchange (ETDEWEB)

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

Martelli, Dario, E-mail: dario.martelli@kcl.ac.uk [Department of Mathematics, King' s College, London, The Strand, London WC2R 2LS (United Kingdom); Sparks, James [Mathematical Institute, University of Oxford, 24-29 St Giles' , Oxford OX1 3LB (United Kingdom)

2013-01-01

251

YBCO coated conductor using biaxially textured clad composite Ni-Mn/Ni-Cr substrate  

International Nuclear Information System (INIS)

A new biaxially textured composite tape of Ni-4.5% Mn/Ni-1.5% Cr was used as a substrate for a YBCO coated conductor through the RABiTS approach. Multi-layer CeO2/YSZ/Y2O3 buffer layers and YBCO film were deposited on the substrate by pulsed laser deposition. The deposition conditions of the buffer layers and the YBCO were studied and compared. Good biaxial textures have been obtained for buffer layers on composite Ni-4.5% Mn/Ni-1.5% Cr substrates. Scanning electron microscopy on sample cross-sections was used to examine the interface and diffusion of oxygen. The uniform formation of an Ni-Mn-O layer between NiO and the Ni-4.5% Mn layer was observed, and the Ni-Mn-O layer restricted the further growth of NiO layer, which was thin and not continuous, within the coated conductor during YBCO deposition at higher temperature and higher oxygen pressure. The Jc of YBCO films on these metal substrates was 1.5 x 106 A cm-2 at 77 K, 0 T

2005-10-01

252

Robust control for a biaxial servo with time delay system based on adaptive tuning technique.  

Science.gov (United States)

A robust control method for synchronizing a biaxial servo system motion is proposed in this paper. A new network based cross-coupled control and adaptive tuning techniques are used together to cancel out the skew error. The conventional fixed gain PID cross-coupled controller (CCC) is replaced with the adaptive cross-coupled controller (ACCC) in the proposed control scheme to maintain biaxial servo system synchronization motion. Adaptive-tuning PID (APID) position and velocity controllers provide the necessary control actions to maintain synchronization while following a variable command trajectory. A delay-time compensator (DTC) with an adaptive controller was augmented to set the time delay element, effectively moving it outside the closed loop, enhancing the stability of the robust controlled system. This scheme provides strong robustness with respect to uncertain dynamics and disturbances. The simulation and experimental results reveal that the proposed control structure adapts to a wide range of operating conditions and provides promising results under parameter variations and load changes. PMID:19345940

Chen, Tien-Chi; Yu, Chih-Hsien

2009-07-01

253

Disclination Loops, Shear Flow, and the Phase Ordering of Uniaxial and Biaxial Nematics.  

Science.gov (United States)

We have extended to bulk nematic systems our previous work(M. Zapotocky, P. Goldbart, N. Goldenfeld, Phys. Rev. E51) (1995) 1216. on phase ordering kinetics in uniaxial and biaxial nematic films. Contrary to some expectations, we do not observe any influence of the non-crossing feature(V. Poénaru and G. Toulouse, J. Phys. (Paris) 8) (1977) 887. of non-abelian disclination lines in biaxial systems on the rate of phase ordering. We attribute this to the absence of entangled disclination loop configurations at late times after the quench, as observed in three-dimensional visualizations of our simulations. We have found that disclination-loop entanglement is also absent in the case of uniaxial nematics. We discuss the degree of generality of and reasons for this striking property of randomly generated defect configurations. Our simulations in the presence of externally imposed shear indicate that if the flow is started after a period of phase ordering without shear flow, the total disclination length in the system first increases (as the defects are stretched by the flow) but then proceeds to decrease, at a rate faster than before the onset of shear flow.

Zapotocky, Martin; Goldbart, Paul M.; Goldenfeld, Nigel

1996-03-01

254

Inclined-substrate deposition of biaxially aligned template films for YBCO-coated conductors  

Science.gov (United States)

Inclined-substrate deposition (ISD) of magnesium oxide (MgO) produces biaxially textured template films at high deposition rates. This process is promising for the fabrication of the second-generation superconducting wires. Biaxially aligned MgO films (?1.5 ?m thick) were deposited on polished Hastelloy C276 (HC) substrates by ISD at deposition rates of 20-100 Å/s. Buffer films were subsequently deposited on these template films, and YBCO films were deposited epitaxially on the substrates by pulsed laser deposition. X-ray pole figure analysis and ?- and ?-scans were used for texture characterization. Good in- and out-of-plane textures were observed, with MgO(0 0 2) ?-scan full-width at half maximum (FWHM) of 9.2° and ?-scan FWHM of 5.4°, respectively. Tc of 90 K with a sharp transition, and Jc?2×10 5 A/cm 2, were obtained on a 0.5 ?m thick, 0.5 cm wide, and 1 cm long YBa 2Cu 3O 7- ? (YBCO) film at 77 K in self-field.

Ma, B.; Li, M.; Fisher, B. L.; Koritala, R. E.; Balachandran, U.

2002-10-01

255

Inclined-substrate deposition of biaxially aligned template films for YBCO-coated conductors.  

Energy Technology Data Exchange (ETDEWEB)

Inclined-substrate deposition (ISD) of magnesium oxide (MgO) produces biaxially textured template films at high deposition rates. This process is promising for the fabrication of the second-generation superconducting wires. Biaxially aligned MgO films ({approx}1.5 {mu}m thick) were deposited on polished Hastelloy C276 (HC) substrates by ISD at deposition rates of 20-100 {angstrom}/s. Buffer films were subsequently deposited on these template films, and YBCO films were deposited epitaxially on the substrates by pulsed laser deposition. X-ray pole figure analysis and {psi}- and {omega}-scans were used for texture characterization. Good in- and out-of-plane textures were observed, with MgO(0 0 2) {phi}-scan full-width at half maximum (FWHM) of 9.2{sup o} and {omega}-scan FWHM of 5.4{sup o}, respectively. T{sub c} of 90 K with a sharp transition, and J{sub c} {approx} 2 x 10{sup 5} A/cm{sup 2}, were obtained on a 0.5 {mu}m thick, 0.5 cm wide, and 1 cm long YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) film at 77 K in self-field.

Ma, B.; Li, M.; Fisher, B. L.; Koritala, R. E.; Balachandran, U. (Energy Technology)

2002-10-15

256

Experimental study of internal conical refraction in a biaxial crystal with Laguerre–Gauss light beams  

Science.gov (United States)

The effect of internal conical refraction (CR) in a biaxial crystal was studied using Laguerre–Gauss light beams {{LG}}_{0}^{\\ell } with \\ell =1 and 2, while the lowest-order {{LG}}_{0}^{0} beam was used as a reference. The transition from ordinary double refraction to CR was examined. It has been shown that double refraction of an {{LG}}_{0}^{\\ell } beam forms two focal spots containing \\ell dark stripes. These stripes evolve into \\ell +1 dark rings over an annular focal image when CR is established, and it results in a fine-structure of \\ell +2 bright focal rings with different intensities. In a sharp contrast to the lowest-order reference, the multiring focal structure has a distinct asymmetry with respect to the focal image plane. It has been shown that bright off-axis ‘hot spot’ can be formed on the far-field profiles of outgoing light beams when the biaxial crystal is slightly tilted, and a small angle between the propagation axis of the beam and the optic axis of the crystal arises. These off-axis light structures emerge as either a charge-one optical vortex or a zero-charge spot with annihilated vorticity. Polarization selection reveals {{J}_{1}} or {{J}_{0}} Bessel-like profiles of the corresponding ‘hot spots’, and a complex pattern of forked fringes in the dark region near the beam core.

Peet, V.

2014-07-01

257

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

LENUS (Irish Health Repository)

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

2011-05-01

258

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2007-01-01

259

Modelling stress-dependent permeability in fractured rock including effects of propagating and bending fractures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The influence of in-situ stresses on flow processes in fractured rock is investigated using a novel modelling approach. The combined finite-discrete element method (FEMDEM) is used to model the deformation of a fractured rock mass. The fracture wall displacements and aperture changes are modelled in response to uniaxial and biaxial stress states. The resultant changes in flow properties of the rock mass are investigated using the Complex Systems Modelling Platform (CSMP++). CSMP++ is used to ...

Latham, J. P.; Xiang, J.; Belayneh, M.; Nick, H. M.; Tsang, C. F.; Blunt, M. J.

2013-01-01

260

Fatigue Assessment of Components Subjected to Non-Proportional Stress Histories  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2013-01-01

 
 
 
 
261

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

2000-01-23

262

Role of Molecular Structure on X-ray Diffraction in Thermotropic Uniaxial and Biaxial Nematic Liquid Crystal Phases  

Energy Technology Data Exchange (ETDEWEB)

X-ray diffraction is one of the most definitive methods to determine the structure of condensed matter phases, and it has been applied to unequivocally infer the structures of conventional calamitic and lyotropic liquid crystals. With the advent of bent-core and tetrapodic mesogens and the discovery of the biaxial nematic phase in them, the experimental results require more careful interpretation and analysis. Here, we present ab-initio calculations of X-ray diffraction patterns in the isotropic, uniaxial nematic, and biaxial nematic phases of bent-core mesogens. A simple Meier-Saupe-like molecular distribution function is employed to describe both aligned and unaligned mesophases. The distribution function is decomposed into two, polar and azimuthal, distribution functions to calculate the effect of the evolution of uniaxial and biaxial nematic orientational order. The calculations provide satisfactory semiquantitative interpretations of experimental results. The calculations presented here should provide a pathway to more refined and quantitative analysis of X-ray diffraction data from the biaxial nematic phase.

Acharya, Bharat R.; Kang, Shin-Woong; Prasad, Veena; Kumar, Satyendra; (Kent); (Platypus)

2009-08-27

263

Role of Molecular Structure on X-ray Diffraction in Uniaxial and Biaxial Phases of Thermotropic Liquid Crystals  

Energy Technology Data Exchange (ETDEWEB)

X-ray diffraction is one of the most definitive methods to determine the structure of condensed matter phases, and it has been applied to unequivocally infer the structures of conventional calamitic and lyotropic liquid crystals. With the advent of bent-core and tetrapodic mesogens and the discovery of the biaxial nematic phase in them, the experimental results require more careful interpretation and analysis. Here, we present ab-initio calculations of X-ray diffraction patterns in the isotropic, uniaxial nematic, and biaxial nematic phases of bent-core mesogens. A simple Meier-Saupe-like molecular distribution function is employed to describe both aligned and unaligned mesophases. The distribution function is decomposed into two, polar and azimuthal, distribution functions to calculate the effect of the evolution of uniaxial and biaxial nematic orientational order. The calculations provide satisfactory semiquantitative interpretations of experimental results. The calculations presented here should provide a pathway to more refined and quantitative analysis of X-ray diffraction data from the biaxial nematic phase.

Acharya, Bharat R.; Kang, Shin-Woong; Prasad, Veena; Kumar, Satyendra; (Kent); (CLCR); (Platypus)

2009-04-29

264

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

International Nuclear Information System (INIS)

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

2007-01-01

265

Orientation-dependent stress relaxation in hetero-epitaxial 3C-SiC films  

Science.gov (United States)

Residual stresses in epitaxial 3C-SiC films on silicon, for chosen growth conditions, appear determined by their growth orientation. Stress evaluation locally with Raman spectroscopy, and across a 150 mm wafer with curvature measurements, indicate that thin films can be grown on Si(100) with residual tensile stresses as low as 150 MPa. However, films on Si(111) retain a considerably higher stress, around 900 MPa, with only minor decrease versus film thickness. Stacking faults are indeed geometrically a less efficient relief mechanism for the biaxial strain of SiC films grown on Si(111) with orientation. Residual stresses can be tuned by the epitaxial process temperatures.

Iacopi, Francesca; Walker, Glenn; Wang, Li; Malesys, Laura; Ma, Shujun; Cunning, Benjamin V.; Iacopi, Alan

2013-01-01

266

Polarized-cathodoluminescence study of stress for GaAs grown selectively on patterned Si(100)  

Science.gov (United States)

The spatial variation of stress tensor in selective-area metalorganic chemical-vapor-deposition-grown GaAs on Si substrate by using a linearly polarized cathodoluminescence (CL) technique has been examined. The polarized CL technique enables a precise determination of the energy positions for the strain-split j = 3/2 valence-band excitonic contributions to the luminescence by a simultaneous deconvolution of two CL spectra that are each taken under different polarization detection conditions; this procedure enables a mapping of the stress tensor. The biaxial in-plane stress (sigma(sub parallel) = sigma(sub perpendicular); where sigma(sub parallel) and sigma(sub perpendicular) are parallel and perpendicular, respectively, to a (110)-oriented mesa edge) is found to decrease from approximately 2.2 to 0.5 kbar as the square pattern size is decreased from 1 mm to 10 micron. Patterns having smaller dimension are found to have an increased luminescence efficiency, indicating a reduction in thermal stress induced dislocation density. The stress decay in the vicinity of edges and corners is found to be modeled well with a bimetal thin-film model, showing an approximately exponential decay in stress. A residual tensile stress (comprised of nonzero sigma(sub perpendicular, shear and peeling stress terms) of 0.5-1.0 kbar is found to exist at the edges and corners of the square GaAs mesas; this result agrees qualitatively with an elastic finite-element analysis. The CL results show that the decay length of stress relief near a pattern edge essentially increases with increasing mesa size. The maximum biaxial stress and residual stress near the mesa edges and corners is found to increase with increasing pattern size. Polarized CL imaging is observed to be sensitive to local deviations from biaxial stress and can be used to map the boundaries of stress contours near mesa edges and defects.

Tang, Y.; Rich, D. H.; Lingunis, E. H.; Haegel, N. M.

1994-09-01

267

Electronic structure and optical properties of CuAlO2 under biaxial strain  

International Nuclear Information System (INIS)

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

2012-06-13

268

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

Directory of Open Access Journals (Sweden)

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

Bolis C.

2012-08-01

269

Biaxial flexure testing of calcium phosphate bioceramics for use in tissue engineering.  

Science.gov (United States)

This study analyzes data from 206 CaP specimens (68 HA, 70 BCP, and 68 beta-TCP) fractured via biaxial flexure testing. Specimens were divided into four groups: (a) Group I, dry; (b) Group II, wet (day 0, immersion time approximately 5-10 s); (c) Group III, after immersion in media for 21 days (day 21); and (d) Group IV, after culturing osteoblasts (OBs) on the surface for 21 days (day 21 with cells). X-ray diffraction verified the presence of minor second phases in HA and beta-TCP while BCP was a biphasic mixture of HA and beta-TCP with minor phases present. The statistical significance (p thermal expansion anisotropy, likely leads to the observed rapid strength decline upon exposure to media found in Groups II, III and IV. PMID:15558613

Meganck, Jeffrey A; Baumann, Melissa J; Case, Eldon D; McCabe, Laura R; Allar, Jaclyn N

2005-01-01

270

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

International Nuclear Information System (INIS)

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

1999-01-01

271

Biaxially aligned YBa 2Cu 3O 7-x thin film tapes  

Science.gov (United States)

We report the formation of biaxially oriented films of yttorium-stabilized ZrO 2 (YSZ) on a polycrystalline, Ni-based alloy (Hastelloy c276) by Ion-Beam-Assisted Deposition (IBAD), and the subsequent a-b plane aligned YBa 2Cu 3O 7-x (YBCO) films deposited by laser ablation. Jc of 6.0×10 4 A/cm 2 (77 K, O T) and 1.4×10 4 A/cm 2 (77 K, 0.6 T) were obtained. A new method to prevent intergranular-weak-links has been developed for application of oxide superconducting thin films, for tape-shaped cables, magnets, magnetic shields, microwave devices, etc.

Iijima, Yasuhiro; Tanabe, Nobuo; Ikeno, Yoshimitsu; Kohno, Osamu

1991-12-01

272

Biaxially aligned YBa2Cu3O7-x thin film tapes  

International Nuclear Information System (INIS)

We report the formation of biaxially oriented films of yttorium-stabilized ZrO2 (YSZ) on a polycrystalline, Ni-based alloy (Hastelloy c276) by Ion-Beam-Assisted Deposition (IBAD), and the subsequent a-b plane aligned YBa2Cu3O7-x (YBCO) films deposited by laser ablation. Jc of 6.0x104A/cm2 (77K, 0 T) and 1.4x104A/cm2 (77K, 0.6 T) were obtained. A new method to prevent intergranular-weak-links has been developed for application of oxide superconducting thin films, for tape-shaped cables, magnets, magnetic shields, microwave devices, etc. (orig.)

1991-12-01

273

Biaxially aligned YBa sub 2 Cu sub 3 O sub 7-x thin film tapes  

Energy Technology Data Exchange (ETDEWEB)

We report the formation of biaxially oriented films of yttorium-stabilized ZrO{sub 2} (YSZ) on a polycrystalline, Ni-based alloy (Hastelloy c276) by Ion-Beam-Assisted Deposition (IBAD), and the subsequent a-b plane aligned YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) films deposited by laser ablation. Jc of 6.0x10{sup 4}A/cm{sup 2} (77K, 0 T) and 1.4x10{sup 4}A/cm{sup 2} (77K, 0.6 T) were obtained. A new method to prevent intergranular-weak-links has been developed for application of oxide superconducting thin films, for tape-shaped cables, magnets, magnetic shields, microwave devices, etc. (orig.).

Iijima, Yasuhiro; Tanabe, Nobuo; Kohno, Osamu (Materials Research Lab., Fujikura Ltd., Tokyo (Japan)); Ikeno, Yoshimitsu (Super-GM, Osaka (Japan))

1991-12-01

274

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

Science.gov (United States)

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

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

1990-01-01

275

DIC-aided biaxial fatigue tests of a 304L steel  

Directory of Open Access Journals (Sweden)

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

Le-Roux J.C.

2010-06-01

276

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

277

Stress at the initial stage of growth for Lennard–Jones films  

Directory of Open Access Journals (Sweden)

Full Text Available

Molecular dynamics simulation was used to study the influence of a relative size of adsorbed and substrate atoms on the stress of growing films. Atoms in the system interact via the Lennard–Jones potential. The simulations were performed at a fixed value of systems temperature. The relative size of deposited atoms was changed in the range from 0.7 to 1.2, relatively to the size of substrate atoms. Proposed modeling allows to explain the behaviour of mean biaxial stress for systems with different sizes of adsorbed atoms and a substrate. For considered systems, significant changes in mean biaxial stress have only first three monolayers.

Tomasz Zientarski

2009-01-01

278

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

Science.gov (United States)

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

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

2003-01-01

279

Nuclear magnetic resonance spectroscopic investigations of phase biaxiality in the nematic glass of a shape-persistent V-shaped mesogen.  

Science.gov (United States)

Deuterium and carbon-13 NMR spectroscopy were used to study both the high temperature uniaxial nematic and the low temperature biaxial nematic glass of a shape-persistent V-shaped mesogen. It was found that biaxial ordering determined in the domains of the latter has symmetry lower than D(2h) and is compatible with C(2h) symmetry or lower. In particular, elements of the ordering matrix including biaxial phase order parameters were determined from (2)H NMR at two temperatures, one just below the glass transition, and the other deep inside the biaxial glass, which allowed for the characterization of the dominant molecular motions at these temperatures. (13)C NMR magic angle spinning sideband patterns, collected both in the high temperature nematic phase and in the nematic glass, clearly show the difference between them in terms of the phase symmetry. PMID:21054053

Figueirinhas, João L; Feio, Gabriel; Cruz, Carlos; Lehmann, Matthias; Köhn, Christiane; Dong, Ronald Y

2010-11-01

280

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

 
 
 
 
281

Incremental stress-strain law for graphite under multiaxial loadings  

International Nuclear Information System (INIS)

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

1981-01-01

282

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have developed on the DIFFABS-SOLEIL beamline a biaxial tensile machine working in synchrotron environment for in-situ diffraction characterization of thin polycrystalline films mechanical response. The machine has been designed to test compliant substrates coated by the studied films under controlled applied strain field. Technological challenges comprise the sample design including fixation of the substrate ends, the related generation of a uniform strain field in the studied (central) v...

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

2010-01-01

283

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 smal...

2013-01-01

284

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

International Nuclear Information System (INIS)

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

2006-06-01

285

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

Energy Technology Data Exchange (ETDEWEB)

Reel-to-reel MOCVD process for continuous growth of electrically conducting buffer layers on biaxially textured Ni5W tapes has been developed. The new buffer layer architechture is presented: 200 nm (La, Ba){sub 2}CuO{sub 4}/40 nm (La, Ba)MnO{sub 3}/Ni5W. Constituting layers with high structural quality have been grown on moving tapes (in plane FWHM {<=} 6{sup 0} and out of plane FWHM {<=} 3{sup 0})

Stadel, O [Institut fuer Oberflaechentechnik (IOT), TU Braunschweig, Bienroder Weg 53, 38108 Braunschweig (Germany); Samoilenkov, S V [Institut fuer Oberflaechentechnik (IOT), TU Braunschweig, Bienroder Weg 53, 38108 Braunschweig (Germany); Muydinov, R Yu [Institut fuer Oberflaechentechnik (IOT), TU Braunschweig, Bienroder Weg 53, 38108 Braunschweig (Germany); Schmidt, J [Institut fuer Oberflaechentechnik (IOT), TU Braunschweig, Bienroder Weg 53, 38108 Braunschweig (Germany); Keune, H [Institut fuer Oberflaechentechnik (IOT), TU Braunschweig, Bienroder Weg 53, 38108 Braunschweig (Germany); Wahl, G [Institut fuer Oberflaechentechnik (IOT), TU Braunschweig, Bienroder Weg 53, 38108 Braunschweig (Germany); Gorbenko, O Yu [Chemistry Department, Moscow State University, 119899 Moscow (Russian Federation); Korsakov, I E [Chemistry Department, Moscow State University, 119899 Moscow (Russian Federation); Melnikov, O V [Chemistry Department, Moscow State University, 119899 Moscow (Russian Federation); Kaul, A R [Chemistry Department, Moscow State University, 119899 Moscow (Russian Federation)

2006-06-01

286

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 wi...

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

287

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.

Garima Joshi

2013-01-01

288

Influence of surface treatments on surface roughness, phase transformation, and biaxial flexural strength of Y-TZP ceramics.  

Science.gov (United States)

The aim of this study was to evaluate the influence of surface grinding and sandblasting on surface roughness, phase chances, and biaxial flexural strength of yttria-stabilized tetragonal zirconia (Y-TZP) materials. Thirty disk specimens of Cercon (C), DentaCAD (DC), Zirkonzahn (ZZ) were fabricated. The specimens were divided into three groups according to surface treatment (control, ground, and sandblasted). Surface roughness was measured, and X-ray diffraction analysis was performed. Finally, biaxial flexural strength was determined. The data was analyzed by two-way ANOVA. Weibull statistics was used to analyze the variability of strength. The effects of surface treatments on surface roughness values were different for each material. X-ray diffraction analysis revealed that control groups of C and ZZ were composed of tetragonal zirconia. Relative amount of monoclinic zirconia (SD) was 7.366 (0.716)% in the DC control group. In all materials, transformation occurred after treatments. Grinding decreased and sandblasting increased the strength of control groups in all materials. Ground C and DC specimens had higher Weibull modulus than control groups while lower m was found for ground ZZ. Sandblasting, resulted in lower m compared with grinding for all materials although increased strength. The roughness and crystalline phase of Y-TZP materials were influenced by surface treatments. Biaxial flexural strength of materials decreased after grinding and increased after sandblasting. The low m of sandblasted groups may indicate further weakening of the materials, resulting in unexpected failures. PMID:19637376

Karakoca, Seçil; Yilmaz, Handan

2009-11-01

289

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

International Nuclear Information System (INIS)

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

1985-01-01

290

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 ...

291

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 ...

292

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

International Nuclear Information System (INIS)

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

2011-07-01

293

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-07-15

294

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

295

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

Science.gov (United States)

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

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

2014-06-01

296

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-01-01

297

Optical emission of biaxial ZnO?ZnS nanoribbon heterostructures  

Energy Technology Data Exchange (ETDEWEB)

The electronic structure and optical properties of biaxial ZnO-ZnS heterostructure nanoribbons (NRs) have been investigated using x-ray absorption near-edge structures (XANES) and x-ray excited optical luminescence (XEOL). The XANES were recorded in total electron yield and wavelength-selected photoluminescence yield across the K- and L{sub 3,2}-edges of zinc and sulfur and the K-edge of oxygen. The XEOL from the NRs exhibit a very weak band-gap emission at 392 nm and two intense defect emissions at 491 and 531 nm. The synchrotron x-ray pulse (- 100 ps, 153 ns repetition rate) was used to track the optical decay dynamics from ZnO-ZnS NR, which can be described by two lifetimes (7.6 and 55 ns). Comparison with similar measurements for ZnO and ZnS nanowires reveals that the luminescence from ZnO-ZnS NRs was dominated by the ZnO component of the NR as the ZnS component contributes little. The implication of this observation is discussed.

Murphy, M.W.; Zhou, X.T.; Ko, J.Y.P.; Zhou, J.G.; Heigl, F.; Sham, T.K.; (UWO)

2009-03-25

298

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

Directory of Open Access Journals (Sweden)

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

Liberti, Michele Santana et al.

2009-01-01

299

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.

Amigó, V.

2010-12-01

300

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

International Nuclear Information System (INIS)

Pebble beds of Tritium breeding ceramic material are investigated within the framework of developing solid breeder blankets for future nuclear fusion power plants. For the thermo-mechanical characterisation of such pebble beds, bed compression experiments are the standard tools. New bi-axial compression experiments on 20 and 30 mm high pebble beds show pebble flow effects much more pronounced than in previous 10 mm beds. Owing to the greater bed height, conditions are reached where the bed fails in cross direction and unhindered flow of the pebbles occurs. The paper presents measurements for the orthosilicate and metatitanate breeder materials that are envisaged to be used in a solid breeder blanket. The data are compared with calculations made with a Drucker-Prager soil model within the finite-element code ABAQUS, calibrated with data from other experiments. It is investigated empirically whether internal bed friction angles can be determined from pebble beds of the considered heights, which would simplify, and broaden the data base for, the calibration of the Drucker-Prager pebble bed models

2002-11-01

 
 
 
 
301

Critical behavior at transitions from uniaxial to biaxial phases in a smectic liquid-crystal mixture.  

Science.gov (United States)

We report results of calorimetric and optical investigations of binary mixtures of rodlike and bent-shaped molecules. We find that the observed critical heat anomaly associated with the smectic-A2 to biaxial smectic-A2b transition is well described with a Fisher-renormalized form of the usual scaling expression. The effect of renormalization is large in this system in part because of the moderately steep slope of the phase boundary (dT(c)/ dX?100 K, where X is the mole fraction of the bent-core molecules) and in part because of the proximity to the tricritical point. The magnitude of heat anomaly at the smectic-A2-smectic-A2b transition showed a drastic decrease as X becomes smaller. Moreover, the nematic-smectic-A2 transitions investigated turned out to be always first order and the transition enthalpy showed only weak dependence on the concentration X. The results imply that the energy fluctuations around the smectic-A2-smectic-A2b transition are very sensitive to the underlying ordering of the smectic-A2 background. PMID:20866637

Sasaki, Y; Ema, K; Le, K V; Takezoe, H; Dhara, S; Sadashiva, B K

2010-07-01

302

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

303

Residual stresses in weld-clad reactor pressure vessel steel  

International Nuclear Information System (INIS)

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

1975-09-01

304

Residual stress and fracture of laminated ceramic membranes  

International Nuclear Information System (INIS)

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

1999-02-05

305

Polymerization shrinkage and stress development in amorphous calcium phosphate/urethane dimethacrylate polymeric composites  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study explores how substituting a new high molecular mass oligomeric poly(ethylene glycol) extended urethane dimethacrylate (PEG-U) for 2-hydroxyethyl methacrylate (HEMA) in photo-activated urethane dimethacrylate (UDMA) resins affects degree of vinyl conversion (DC), polymerization shrinkage (PS), stress development (PSSD) and biaxial flexure strength (BFS) of their amorphous calcium phosphate (ACP) composites. The composites were prepared from four types of resins (UDMA, PEG-U, UDMA/HE...

Antonucci, J. M.; Regnault, W. F.; Skrtic, D.

2010-01-01

306

Biaxial Cyclic Hardening of Annealed Copper Cylinders Evaluated by Deformation Plasticity Theories.  

Science.gov (United States)

Hollow and solid circular cylinders of annealed OFHC copper were subjected to cyclic proportional strain histories. The stress-strain histories for different strain paths were correlated on the basis of Tresca and Mises effective stresses and strains, and...

H. S. Lamba O. M. Sidebottom

1976-01-01

307

Non-destructive measurement of residual stresses in U-0.8 wt.% Ti by neutron diffraction  

International Nuclear Information System (INIS)

The macroscopic residual stress distribution in ?-quenched and stress levelled U-0.8wt% Ti alloy tubes was studied using neutron diffraction techniques. Residual strains were evaluated from the difference in d-spacings measured in the tubes and in small reference samples machined from each tube. Residual stresses were calculated with the isotropic bulk value of the elastic constraints for polycrystalline ?-U. Quenching from the ? field resulted in a nearly equi-biaxial stress state at every point across the wall thickness of the tube. The magnitude of the radial stress was very small compared with that of the axial and hoop stresses which were compressive at the surfaces and tensile in the interior. Stress levelling relieved almost completely the hoop residual stress without affecting the radial stress. The axial residual stress becomes tensile through the wall thickness and remains constant at about 20% of its magnitude in the as-quenched condition

1989-12-02

308

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 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). Metade dos espécimes for...

2012-01-01

309

Influences of wear material, fault roughness and loading rate on stick-slip behavior revealed by large-scale biaxial friction experiments  

Science.gov (United States)

We investigated the stick-slip events during large-scale biaxial friction experiments. We used a pair of large square-column rock samples, whose contact area was 1.5 m x 0.5 m (for detailed features of the apparatus, please refer to Fukuyama et al., 2012 in this meeting). The experiments were carried out with the loading rates from 0.0125 mm/s to 1 m/s under the constant normal stress between 0.13 and 1.3 MPa. The maximum displacement was 0.4 m. The experiments were repeatedly carried out under various mechanical conditions, and the total amount of displacement attained to 77 m. The sliding surfaces were flattened within 24 ?m undulation before the series of experiments. With the experiments proceeding, the sliding surfaces were evolved and generated wear materials. To investigate the effect of wear material on friction behavior, we sometimes kept and sometimes removed the wear material on the sliding surfaces. We observed a variation of stress drops even under the same mechanical condition, which could be caused by the change in the state of sliding surface, i.e. wear material and roughness on the surface since the machine characteristics remained the same during the experiments. Unfortunately, since we could not make direct measurements of the amount of wear material and fault roughness, we introduced a parameter W related to the amount of wear material and defined as the accumulation of product of normal stress (N) and displacement (D). This is derived from the theoretical examination that the thickness of gouge layer is proportional to N and D (Scholz, 1987, Geology). We defined another parameter R related to fault roughness. Since ND is thought to be the shear damage during each experiment, its total accumulation can be equal to R whereas W is reset to 0 after removing the wear material. We found that the stress drop is negatively proportional to both R and W independent of loading rate, and the amount of stress drop can be expressed as a multivariate function of R and W. This finding is consistent with the previous study by Anthony and Marone (2005, JGR), who reported that stress drops decrease with increasing thickness of gouge layer and surface roughness. In particular, the correlation at loading rate of 100 mm/s is so high (the coefficient of determination by multi-regression attains to 0.87). This indicates that the stick-slip behavior is dominantly controlled by wear material and fault roughness at this loading rate. In contrast, as to the dependence of stress drop on the loading rate, we observed an opposite relation to that by previous studies whose loading range was between 0.1 ?m/s and 3 mm/s (Mair et al., 2002, JGR; Anthony and Marone, 2005, JGR); the stress drop increased with the increase of loading rate from 0.1 mm/s to 100 mm/s in the present experiments. This positive correlation comes from the decreases in residual coefficient of friction with the loading rate because the peak coefficients of friction are almost constant at these loading rates. This discrepancy may come from the differences in the loading rate and the velocity weakening process of rock friction (e.g. Di Toro et al., 2011, Nature), though there remain other possibilities such as the machine stiffness.

Yamashita, F.; Fukuyama, E.; Mizoguchi, K.; Togo, T.

2012-12-01

310

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-06-07

311

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

Energy Technology Data Exchange (ETDEWEB)

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

2013-10-15

312

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

313

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

International Nuclear Information System (INIS)

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

2013-10-15

314

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

International Nuclear Information System (INIS)

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

2011-06-07

315

Estimation of step-by-step induced stress in a sequential process integration of nano-scale SOS MOSFETs with high-k gate dielectrics  

Science.gov (United States)

The current work proposes a novel technique to incorporate process-induced uni-axial stress for significant mobility boosting in high-performance metal-oxide-semiconductor field-effect-transistors. It has been shown that two existing standard techniques, namely, silicon-on-sapphire and high-k gate dielectrics can be combined to develop such technology. Sapphire has very high elastic constant and thermal expansion coefficient, thereby capable of inducing a significant amount of stress which is observed to be biaxial in nature. However, with the incorporation of different materials during process integration, such biaxial stress is gradually changed to uni-axial nature. The high-k gate dielectric plays the key role in converting the biaxial stress to uni-axial. Several high-k gate dielectrics have been studied and titanium oxide (TiO2) is observed to maximize the induced stress and also effective to convert it to uni-axial. A final average longitudinal channel stress of 0.73 GPa has been obtained.

Chatterjee, Sulagna; Nag Chowdhury, Basudev; Das, Anindita; Chattopadhyay, Sanatan

2013-12-01

316

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-03-15

317

High nematic ordering in a bent-core smectogen showing a biaxial nematic phase: A 13C NMR study  

Science.gov (United States)

Carbon-13 NMR spectroscopy has been used to probe the orientational ordering of a bent-core liquid crystal A131. Both the carbon chemical shift tensors in a rotating solid sample and chemical shifts from the aligned mesophases were determined. These results allow us to probe the local order parameters of the five phenyl rings in the liquid crystalline molecule. It is found that the conformation and ordering of the bent-shaped core significantly change between the uniaxial and biaxial nematic phases, with the highest local nematic order not associated to the central ring in this azo substituted bent-core mesogen.

Dong, Ronald Y.; Kumar, Satyendra; Prasad, Veena; Zhang, Jing

2007-11-01

318

Interplay of point defects, biaxial strain, and thermal conductivity in homoepitaxial SrTiO3 thin films  

International Nuclear Information System (INIS)

Separating out effects of point defects and lattice strain on thermal conductivity is essential for improvement of thermoelectric properties of SrTiO3. We study relations between defects generated during deposition, induced lattice strain, and their impact on thermal conductivity ? in homoepitaxial SrTiO3 films prepared by ion-beam sputtering. Lowering the deposition temperature gives rise to lattice expansion by enhancement of point defect density which increases the hardness of the films. Due to a fully coherent substrate-film interface, the lattice misfit induces a large biaxial strain. However, we can show that the temperature dependence of ? is mainly sensitive on the defect concentration.

2012-02-06

319

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Adding heat to glass ionomers during setting might improve mechanical properties. The aim was to compare the biaxial flexural strength (BFS) between and within four glass ionomers, by time of exposure to a high-intensity LED light-curing unit. Materials and methods. Samples of Fuji 9 Gold Label, Ketac Molar Easymix, ChemFil Rock, and the EQUIA system were divided into three treatment groups (n = 30): without heating (Group 1), heated with LED lamp of 1400?mW/cm2 for 30?s while setting (Gr...

2013-01-01

320

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 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...

2010-01-01

 
 
 
 
321

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

International Nuclear Information System (INIS)

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

2013-01-23

322

Controlled biaxial strain-rate test results from unirradiated 20% CW 316 stainless steel cladding at constant temperature  

International Nuclear Information System (INIS)

Constant temperature controlled biaxial strain-rate (CBSR) tests were performed on unirradiated 20% CW 316 stainless steel reactor cladding. Tests were made at hoop strain-rates of 1.2 x 10-5/s, 1.2 x 10-4/s, 6 x 10-4/s, and 1.2 x 10-3/s. For each of these strain rates, tests were performed at 4250C, 5400C, and 6500C. The data from these tests are examined and compared with previously reported tensile data. A simple relationship between tensile and CBSR tests is developed, allowing easy correlation of the CBSR results

1979-02-21

323

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

324

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 SciELO Venezuela | Language: Spanish 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 experimentales en el Laboratorio de Mecánica Estructural de la Universidad Centroccidental Lisandro Alvarado. El modelo fue calibrado mediante simulaciones numéricas de estos ensayos, encontrándose una buena concordancia entre las pruebas experimentales y las simulaciones numéricas. Abstract in english This paper presents a general formulation for the analysis of steel hollow structural beams prone to local buckling subjected to biaxial bending. The model has been developed within the framework of Lumped Damage Mechanics. In this approach, the models are based on methods of Continuum Damage Mechan [...] ics and the concept of plastic hinge. The model was implemented in a commercial finite element program. In order to calibrate the model, a set of experimental tests were carried out in the Structural Mechanics Laboratory at Universidad Centroccidental Lisandro Alvarado. The model was evaluated by the numerical simulation of these tests, obtaining a good agreement between the experimental tests and the numerical simulations.

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

325

Creep strength variation with applied stress on stress-relieved and recrystallized Zry-4 cladding  

Energy Technology Data Exchange (ETDEWEB)

The bi-axial tube creep test was carried out using the stress-relieved and fully recrystallized low tin Zry-4 materials under the the temperature range of 360-400 .deg. C and applied hoop stress of 90-150MPa. The diametral creep strength of Rx tube was better than the SR tube at the 90 and 120MPa stress conditions, while the trend was reversed when the stress was applied at 150MPa. The stress exponents of SR and Rx tubes showed stress and temperature dependency and these values were 3-5 and 4.5-7, respectively. The creep activation energies of SR and Rx tubes also showed stress dependency, and these were determined as 45-65kcal/mole and 50-70kcal/mole, respectively. The deformed structure of SR tube was maintained in the crept specimens, and well developed dislocation cells and networks were observed both in the SR and Rx materials. To explain the stress dependency of SR and Rx tubes, the concept of obstacle density distribution with obstacle strength was proposed. As a result, the obstacle density of SR tube would be decreased slowly, whilst that of Rx tube decreased rapidly with obstacle strength increase.

Nam, C.; Choi, B. K.; Jeong, Y. W.; Jeong, Y. H. [KAERI, Taejon (Korea, Republic of)

2001-05-01

326

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

International Nuclear Information System (INIS)

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

2006-11-01

327

Anomalous Behavior in the Crossover between the Negative and Positive Biaxial Nematic Mesophases in a Lyotropic Liquid Crystal.  

Science.gov (United States)

A novel quaternary lyotropic liquid-crystalline mixture of dodecyltrimethylammonium bromide (DDTMABr)/sodium bromide/1-dodecanol/water, presenting the biaxial nematic phase (NB ) in addition to two uniaxial discotic (ND ) and calamitic (NC ) nematic ones, was synthesized. The partial phase diagram of this new mixture was constructed as a function of the DDTMABr molar-fraction concentration. The phase transitions from uniaxial to biaxial nematic phases were studied by means of the temperature dependence of the optical birefringence. In a particular region of the phase diagram, anomalous behavior was observed in the crossover from ${N_{\\rm{B}}^ - }$ to ${N_{\\rm{B}}^ + :}$ the contrast of the conoscopic fringes, which allows the birefringence measurements, almost vanishes, and the sample loses its alignment. This behavior, which was not observed before in lyotropics, was interpreted as a decrease in the mean diamagnetic susceptibility anisotropy (??) of the sample, which was related to the shape anisotropy of the micelles. Small-angle X-ray scattering measurements were performed to evaluate the micellar shape anisotropy; these revealed that this mixture presented a smaller shape anisotropy than those of other lyotropic micellar systems presenting the NB phase. PMID:24692308

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

2014-05-19

328

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

329

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

Energy Technology Data Exchange (ETDEWEB)

A unique, three-dimensional (3D), biaxially textured, MgO, nanofence comprised of single crystal MgO nanobelt segments or links was synthesized via epitaxial growth on (100) SrTiO{sub 3} substrates. Individual single crystal MgO nanobelt segments comprising the nanofence have a square cross-section with dimensions in the range of 10-20 nm and with lengths in the range from 100 nm up to 1 {mu}m. X-ray diffraction shows that the 3D MgO nanofence has an epitaxial relation with (100) SrTiO{sub 3} substrates with a cube-on-cube, {l_brace}100{r_brace}(100) orientation and with values of the full width at half-maximum of the (200) {omega}-scan and the (110) {psi}-scan at 4.5{sup 0} and 5.5{sup 0}, respectively. Such a biaxially textured oxide nanofence with single crystal segments can be used as a 3D nanotemplated substrate for epitaxial growth of wide-ranging, 3D, electronic, magnetic and electromagnetic nanodevices.

Wee, Sung Hun; Goyal, Amit; More, Karren L; Specht, Eliot [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)], E-mail: goyala@ornl.gov

2009-05-27

330

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

Energy Technology Data Exchange (ETDEWEB)

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

Deng Ruopeng; Muralt, Paul; Gall, Daniel [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Ceramics Laboratory, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2012-09-15

331

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-08-15

332

Stress Management  

Science.gov (United States)

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

333

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

334

Biaxial flexural strength and phase transformation of Ce-TZP/Al2O3 and Y-TZP core materials after thermocycling and mechanical loading  

Science.gov (United States)

PURPOSE The purpose of the present study was to evaluate the effect of thermocycling and mechanical loading on the biaxial flexural strength and the phase transformation of one Ce-TZP/Al2O3 and two Y-TZP core materials. MATERIALS AND METHODS Thirty disc-shaped specimens were obtained from each material. The specimens were randomly divided into three groups (control, thermocycled, and mechanically loaded). Thermocycling was subjected in distilled water for 10000 cycles. Mechanical loading was subjected with 200 N loads at a frequency of 2 Hz for 100000 times. The mean biaxial flexural strength and phase transformation of the specimens were tested. The Weibull modulus, characteristic strength, 10%, 5% and 1% probabilities of failure were calculated using the biaxial flexural strength data. RESULTS The characteristic strengths of Ce-TZP/Al2O3 specimens were significantly higher in all groups compared with the other tested materials (P<.001). Statistical results of X-ray diffraction showed that thermocycling and mechanical loading did not affect the monoclinic phase content of the materials. According to Raman spectroscopy results, at the same point and the same material, mechanical loading significantly affected the phase fraction of all materials (P<.05). CONCLUSION It was concluded that thermocycling and mechanical loading did not show negative effect on the mean biaxial strength of the tested materials.

Bankoglu Gungor, Merve; Ayd?n, Cemal; Karakoca Nemli, Secil; Turhan Bal, Bilge; T?ras, Tulay

2014-01-01

335

Elasto-plastic behaviour of a thin cylinder under thermal stress cycling  

Energy Technology Data Exchange (ETDEWEB)

A simple biaxial model is chosen to represent the stress state of a thin cylinder and the elasto-plastic behaviour under thermal stress cycling is studied to determine: 1. shakedown limits, 2. plastic cycling limits, 3. magnitude of cyclic strains and ratchet strains, 4. strain ratios in various regimes. The studies have been carried out for two material models: elastic-perfectly plastic and Prager-hardening. Results are given in the form of graphs and compared with the results of uniaxial models.

Govindarajan, S. (Reactor Research Centre, Kalpakkam (India). Fast Reactor Group); Sundararajan, V. (Indian Inst. of Tech., Kanpur. Dept. of Mechanical Engineering and Nuclear Centre)

1983-04-01

336

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

CERN Multimedia

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

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

2000-01-01

337

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

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

338

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

Science.gov (United States)

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

Owerre, S. A.; Paranjape, M. B.

2014-05-01

339

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

Science.gov (United States)

The complex dielectric function of biaxially strained Ge1-xSnx (0 ? x ? 0.17) alloys grown on Ge (100) has been determined by spectroscopic ellipsometry from 1.2 to 4.7 eV. The effect of substitutional Sn incorporation and the epitaxial strain on the energy transitions E1, E1 + ?1, E0', and E2 of GeSn alloys is investigated. Our results indicate that the strained GeSn alloys show Ge-like electronic bandstructure with all the transitions shifted downward due to the alloying of Sn. The strain dependence of E1 and E1 + ?1 transitions is explained using the deformation potential theory, and values of -5.4 ± 0.4 eV and 3.8 ± 0.5 eV are obtained for the hydrostatic and shear deformation potentials, respectively.

Richard D'Costa, Vijay; Wang, Wei; Zhou, Qian; Soon Tok, Eng; Yeo, Yee-Chia

2014-01-01

340

Interplay of point defects, biaxial strain, and thermal conductivity in homoepitaxial SrTiO{sub 3} thin films  

Energy Technology Data Exchange (ETDEWEB)

Separating out effects of point defects and lattice strain on thermal conductivity is essential for improvement of thermoelectric properties of SrTiO{sub 3}. We study relations between defects generated during deposition, induced lattice strain, and their impact on thermal conductivity {kappa} in homoepitaxial SrTiO{sub 3} films prepared by ion-beam sputtering. Lowering the deposition temperature gives rise to lattice expansion by enhancement of point defect density which increases the hardness of the films. Due to a fully coherent substrate-film interface, the lattice misfit induces a large biaxial strain. However, we can show that the temperature dependence of {kappa} is mainly sensitive on the defect concentration.

Wiedigen, S.; Kramer, T.; Knorr, I.; Nee, N.; Hoffmann, J.; Volkert, C. A.; Jooss, Ch. [University of Goettingen, Institute of Materials Physics, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany); Feuchter, M.; Kamlah, M. [Karlsruhe Institute of Technology, Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

2012-02-06

 
 
 
 
341

Growth of Strongly Biaxially Aligned MgB2 Thin Films on Sapphire by Post-annealing of Amorphous Precursors  

CERN Document Server

MgB2 thin films were cold-grown on sapphire substrates by pulsed laser deposition (PLD), followed by post-annealing in mixed, reducing gas, Mg-rich, Zr gettered, environments. The films had Tcs in the range 29 K to 34 K, Jcs (20K, H=0) in the range 30 kA/cm2 to 300 kA/cm2, and irreversibility fields at 20 K of 4 T to 6.2 T. An inverse correlation was found between Tc and irreversibility field. The films had grain sizes of 0.1-1 micron and a strong biaxial alignment was observed in the 950C annealed film.

Berenov, A V; Qi, X; Bugoslavsky, Y; Cohen, L F; Jo, M H; Stelmashenko, N A; Tsaneva, V N; Kambara, M; Babu, N H; Cardwell, D A; Blamire, M G; MacManus-Driscoll, J L

2001-01-01

342

Study of the growth of biaxially textured CeO{sub 2} films during ion-beam-assisted deposition  

Energy Technology Data Exchange (ETDEWEB)

Biaxially textured CeO{sub 2} films were deposited on Hastelloy C276 substrates at room temperature using ion-beam-assisted e-beam evaporation with the ion beam directed at 55 deg. to the normal of the film plane. The crystalline structure and in-plane orientation of films were investigated by x-ray diffraction 2{theta}-scan and {phi}-scan. The orientation of the films was studied as a function of ion-to-atom ratio and film thickness. The ion-to-atom ratio was varied by independently adjusting the deposition rate and the ion current density. Under optimum condition, (200) textured CeO{sub 2} films have been successfully grown on Hastelloy C276.

Kim, Chang Su [Department of Metallurgical Engineering, Yonsei University, Seodaemoon Ku, Shinchon Dong 134, Seoul 120-749 (Korea, Republic of); Jo, Sung Jin [Department of Metallurgical Engineering, Yonsei University, Seodaemoon Ku, Shinchon Dong 134, Seoul 120-749 (Korea, Republic of); Jeong, Soon Moon [Department of Metallurgical Engineering, Yonsei University, Seodaemoon Ku, Shinchon Dong 134, Seoul 120-749 (Korea, Republic of); Kim, Woo Jin [Department of Metallurgical Engineering, Yonsei University, Seodaemoon Ku, Shinchon Dong 134, Seoul 120-749 (Korea, Republic of); Baik, Hong Koo [Department of Metallurgical Engineering, Yonsei University, Seodaemoon Ku, Shinchon Dong 134, Seoul 120-749 (Korea, Republic of); Lee, Se Jong [Department of Materials Science and Engineering, Kyungsung University, Busan 608-736 (Korea, Republic of); Song, Kie Moon [Department of Applied Physics, Konkuk University, Chungju 380-701 (Korea, Republic of)

2005-03-01

343

Study of the growth of biaxially textured CeO2 films during ion-beam-assisted deposition  

Science.gov (United States)

Biaxially textured CeO2 films were deposited on Hastelloy C276 substrates at room temperature using ion-beam-assisted e-beam evaporation with the ion beam directed at 55° to the normal of the film plane. The crystalline structure and in-plane orientation of films were investigated by x-ray diffraction 2?-scan and phgr-scan. The orientation of the films was studied as a function of ion-to-atom ratio and film thickness. The ion-to-atom ratio was varied by independently adjusting the deposition rate and the ion current density. Under optimum condition, (200) textured CeO2 films have been successfully grown on Hastelloy C276.

Kim, Chang Su; Jo, Sung Jin; Jeong, Soon Moon; Kim, Woo Jin; Baik, Hong Koo; Lee, Se Jong; Song, Kie Moon

2005-03-01

344

Study of the growth of biaxially textured CeO2 films during ion-beam-assisted deposition  

International Nuclear Information System (INIS)

Biaxially textured CeO2 films were deposited on Hastelloy C276 substrates at room temperature using ion-beam-assisted e-beam evaporation with the ion beam directed at 55 deg. to the normal of the film plane. The crystalline structure and in-plane orientation of films were investigated by x-ray diffraction 2?-scan and ?-scan. The orientation of the films was studied as a function of ion-to-atom ratio and film thickness. The ion-to-atom ratio was varied by independently adjusting the deposition rate and the ion current density. Under optimum condition, (200) textured CeO2 films have been successfully grown on Hastelloy C276

2005-03-01

345

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.

2010-02-01

346

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

347

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

Science.gov (United States)

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

Lu, Xiancong; Chen, Lixiang

2013-04-01

348

Managing Stress  

Medline Plus

Full Text Available ... stopping or perceived as non-stopping, the body never gets a chance to relax. This causes constant ... bad stress” or “chronic stress.” Risks of Stress Never-ending stress can lead to a variety of ...

349

Manage Stress  

Science.gov (United States)

... Conditions and Diseases > Heart Health > Manage Stress Manage Stress The Basics Take Action! Ver en español Content ... on: May 27, 2014 The Basics Not all stress is bad. Stress can help protect you in ...

350

Performance characterization of a single bi-axial scanning MEMS mirror-based head-worn display  

Science.gov (United States)

The NomadTM Personal Display System is a head-worn display (HWD) with a see-through, high-resolution, high-luminance display capability. It is based on a single bi-axial scanning MEMS mirror. In the Nomad HWD system, a red laser diode emits a beam of light that is scanned bi-axially by a single MEMS mirror. A diffractive beam diffuser and an ocular expand the beam to form a 12mm exit pupil for comfortable viewing. The Nomad display has an SVGA (800x600) resolution, 60Hz frame rate, 23-degree horizontal field of view (FOV) and 3:4 vertical to horizontal aspect ratio, a luminance of 800~900 foot-Lamberts, see-through capability, 30mm eye-relief distance, and 1-foot to infinity focusing adjustment. We have characterized the performance parameters, such as field of view, distortion, contrast ratio (4x4 black and white checker board), modulation depth, exit pupil size, eye relief distance, maximum luminance, dynamic range ratio (full-on-to-full-off ratio), dimming ratio, and luminance uniformity at image plane. The Class-1 eye-safety requirements per IEC 60825-1 Amendment 2 (CDRH Laser Notice No. 50) are analyzed and verified by experiments. The paper describes all of the testing methods and set-ups as well as the representative test results. The test results demonstrate that the Nomad display is an eye-safe display product with good image quality and good user ergonomics.

Liang, Minhua

2002-06-01

351

Nucleation and growth of stress relief patterns in sputtered molybdenum films  

International Nuclear Information System (INIS)

Stress relief patterns in sputtered molybdenum films were studied by Nomarski differential interference contrast microscope. As a result of the very large biaxial compressive stress in the film plane, ranging from E/16 to E/130 (where E is Young's modulus), the films were partially buckled and detached from the substrate, exhibiting one of two modes of stress relief pattern, wrinkled spots or wavy ridges. The former mode is a nucleation pattern and the latter a growth pattern. The transition between the two can be interpreted in terms of the stress intensity factor K_I at the head of the gap formed due to stress between the film and the substrate. K_I can be regarded as measure of the bond strength between the film and the substrate. (author)

1986-01-01

352

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

International Nuclear Information System (INIS)

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

2012-05-14

353

Effect of biaxial loading and geometry on prediction of low-cycle fatigue life  

International Nuclear Information System (INIS)

Data to predict failure by low-cycle fatigue are mainly based on uniaxial constant amplitude tests on solid specimens, although in practically all cases the state of stress of a reactor component is multiaxial. The effect of multiaxiality has been investigated on thin-walled tubular specimens. For the uniaxial loading condition a comparison has been made with tests on solid specimens. The investigated materials were 18Cr-11Ni steel (type AISI 304) at 200C and 5500C and Nb-stabilized 2 1/4Cr1Mo steel at 5000C. The thin-walled tubular specimens have been loaded by combinations of cyclic axial load and cyclic torsion, with which a range of principal stress ratios between -1 2/sigma1 2/?epsilon1 <= -0.5 could be achieved. (orig.)

1979-08-21

354

Swelling effects in dynamic equi-biaxial testing of EPDM elastomers by the bubble inflation method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The thesis describes the effect of oil swelling on the fatigue life of EPDM under conditions of multi-axial fatigue using bubble inflation. The motivation for the research is outlines, along with a review of previous research conducted on the topic. Initial test results are presented and the evolution of the procedure for the final set of tests is described. One principal requirement identified when carrying out the fatigue tests was the need for constant stress control. Following development...

2008-01-01

355

Biaxial Thermal Creep of V-4Cr-4Ti AT 700C and 800C  

Energy Technology Data Exchange (ETDEWEB)

A study of the thermal creep properties of V-4Cr-4Ti 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 uniaxial yield strength. Specimens were heated to 700 and 800C in an ultra-high vacuum furnace and periodically removed to measure the change in OD with a high-precision laser profilometer. The secondary creep rate was found to be power-law dependent on the applied stress with a stress exponent of 3.7 at 700C and 2.7 at 800C. The average activation energy for creep of V-4Cr-4Ti was 299 kJ/mole, which is quite close to the activation energy for self-diffusion in pure vanadium in this temperature regime. The predominant mechanism of creep deformation for the conditions employed in this study is most likely climb assisted dislocation motion.

Kurtz, Richard J.; Hamilton, Margaret L.

2000-09-01

356

Anisotropy of tensile stresses and cracking in nonbasal plane AlxGa1-xN/GaN heterostructures  

International Nuclear Information System (INIS)

AlxGa1-xN films grown on nonpolar m (1100) and (1122) semipolar orientations of freestanding GaN substrates were investigated over a range of stress states (x?0.17). Cracking on the (0001) plane was observed beyond a critical thickness in the (1100) oriented films, while no cracking was observed for (1122) films. Theoretical analysis of tensile stresses in AlxGa1-xN for the relevant planes revealed that anisotropy of in-plane biaxial stress for the nonpolar (1100) planes results in the highest normal stresses on the c-planes, consistent with experimental observations. Shear stresses are significant in the semipolar case, suggesting that misfit dislocation formation provides an alternative mechanism for stress relief.

2010-01-25

357

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-01-01

358

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

Science.gov (United States)

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

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

2012-03-01

359

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

CERN Document Server

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

360

Influence of the glass-fiber/matrix interface quality on the monoaxial and biaxial mechanical behavior of composite plates and tubes  

Science.gov (United States)

The behavior of composite samples differing in interface quality was investigated under the following types of loading: monoaxial tension with monitoring of acoustic emission spectra; interlaminar shear; crack initiation and crack growth in mode I; viscoelasticity in bending; and biaxial monotonic tension and cylic loading with increasing amplitude and dynamic fatigue. In general, the results demonstrate a strong influence of the fiber/matrix interface on the mechanical behavior of the composites.

Krawczak, Patricia; Pabiot, Jose

 
 
 
 
361

Stress distribution in GaN nanopillars using confocal Raman mapping technique  

Science.gov (United States)

In this Letter, high-resolution confocal Raman mapping of stress distribution in etched and re-grown GaN nanopillar structures is investigated. Results of the E2(high) phonon line mapping of the top surfaces of individual nanopillars reveal differences in stress between both the center and edge of the nanopillar top surfaces and between the etched and re-grown GaN nanopillar structures. In-plane biaxial compressive stress with the values of 0.36-0.42 GPa and 0.49-0.54 GPa is observed at the center of etched and re-grown GaN nanopillars, respectively. The in-plane biaxial compressive stress decreases from center to edge in re-grown GaN nanopillar due to the tilted facets. Also, the A1(LO) phonon frequency increases from center to edges, or tilted facets, due to the tilt of the c-axis of re-grown GaN nanopillar.

Nagarajan, S.; Svensk, O.; Lehtola, L.; Lipsanen, H.; Sopanen, M.

2014-04-01

362

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

Science.gov (United States)

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

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

1972-01-01

363

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 ...

364

Handling Stress  

Science.gov (United States)

... Breastfeeding This information in Spanish ( en español ) Handling stress Did you know? Breastfeeding can help mothers relax ... stress. Return to top More information on Handling stress Explore other publications and websites Breastfeeding FAQs: Sleep — ...

365

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 ...

366

Managing Stress  

Medline Plus

Full Text Available ... stress they may experience: • Headaches • Tense muscles • Shaky hands • Fatigue • Insomnia • Heartburn Stressed people may also feel: • ... Stress can cause muscle knots in the back, hands, and different muscle groups. A massage therapist can ...

367

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)

2011-07-01

368

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

CERN Document Server

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

369

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

Energy Technology Data Exchange (ETDEWEB)

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

Cardelli, E. [Department of Industrial Engineering, University of Perugia, I-06125 Perugia (Italy); Center for Electric and Magnetic Applied Research (Italy); Faba, A., E-mail: faba@unipg.it [Department of Industrial Engineering, University of Perugia, I-06125 Perugia (Italy); Center for Electric and Magnetic Applied Research (Italy)

2014-02-15

370

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

International Nuclear Information System (INIS)

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

2014-02-15

371

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

Science.gov (United States)

In this contribution, we present the application potentiality of biaxial Q-shearing of (27)Al 3QMAS NMR spectra in the analysis of structural defects of aluminium units in aluminosilicates. This study demonstrates that the combination of various shearing transformations of the recorded (27)Al 3QMAS NMR spectra enables an understanding of the broadening processes of the correlation signals of disordered framework aluminosilicates, for which a wide distribution of (27)Al MAS NMR chemical shifts and quadrupolar parameters (i.e., second-order quadrupolar splitting and quadrupole-induced chemical shifts) can be expected. By combining the suitably selected shearing transformation procedures, the mechanisms of the formation of local defects in aluminosilicate frameworks, including Al/Si substitution effects in the next-nearest neighbouring T-sites, variations in bond angles, and/or variations in the physicochemical nature of charge-balancing counter-ions, can be identified. The proposed procedure has been extensively tested on a range of model aluminosilicate materials (kyanite, ?-alumina, metakaolin, analcime, chabazite, natrolite, phillipsite, mordenite, zeolite A, and zeolite Y). PMID:24333044

Kobera, Libor; Brus, Jiri; Klein, Petr; Dedecek, Jiri; Urbanova, Martina

2014-01-01

372

Fabrication of High Current YBa_2Cu_3O_7_-_y Coated Conductors Using Rolling-Assisted Biaxially Textured Substrates  

International Nuclear Information System (INIS)

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

1998-06-01

373

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

2013-01-01

374

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

CERN Document Server

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

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

2014-01-01

375

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

International Nuclear Information System (INIS)

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

2003-01-01

376

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

2011-05-15

377

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

CERN Document Server

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

Martins, P; Brida, S; Barbier, D

2008-01-01

378

Determination of Stress-Strain Curves of Sheet Metals by Hydraulic Bulge Test  

Science.gov (United States)

The paper is focused on the determination of the biaxial stress-strain curves by hydraulic bulging tests with circular die using a new methodology. This methodology is based on a modified version of Kruglov's formula for the calculation of the polar thickness that takes into account the non-uniformity of the strain distribution on the dome surface. In order to validate the methodology, the authors have performed both stepwise and continuous bulging experiments using the optical measurement system ARAMIS. The comparison with experimental data shows an improved accuracy of the modified Kruglov's formula.

L?z?rescu, Lucian; Com?a, Dan Sorin; Banabic, Dorel

2011-05-01

379

Study of Structure and Intrinsic Stresses of Ge Thin Films on GaAs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of film growth rate on the structure and intrinsic stresses of thin (~100 nm) Ge films grown on GaAs(100) substrates was investigate by High Resolution X-Ray Diffraction (HRXRD). The Ge films were deposited onto GaAs using thermal evaporation of Ge in the vacuum. It was shown that pseudomorphic films with good structural quality can be obtained by this growth technique. We found out that the films have biaxial deformations due to coherent interface and Poisson ratio. The films are...

Mitin V.F.; Kholevchuk V.V.; Kladko V.P.; Kuchuk A.V.; Lytvyn P.M.; Matveeva L.A.

2013-01-01

380

On the determination of Poisson’s ratio of stressed monolayer and bilayer submicron thick films  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, the bulge test is used to determine the mechanical properties of very thin dielectric membranes. Commonly, this experimental method permits to determine the residual stress (s0) and biaxial Young’s modulus (E/(1-u)). Associating square and rectangular membranes with different length to width ratios, the Poisson’s ratio (u) can also be determined. LPCVD Si3N4 monolayer and Si3N4/SiO2 bilayer membranes, with thicknesses down to 100 nm, have been characterized giving results i...

Martins, P.; Malhaire, C.; Brida, S.; Barbier, D.

2008-01-01

 
 
 
 
381

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, ...

382

Effects of stress on swelling in reactor fuel cladding  

International Nuclear Information System (INIS)

The purpose of this report is to describe the effect of stress on swelling in both annealed and 20% cold worked 316 stainless steel. An effect of stress on swelling in irradiated metals has been postulated for some time. Low fluence data confirmed that indeed a tensile stress can increase swelling in irradiated annealed 316 stainless steel and that the maximum swelling occurs at an intermediate stress level which is approximately equal to the proportional elastic limit of the material. The specimens discussed above were examined by transmission electron microscopy and an effect of stress on the microstructure of the annealed and 20% cold worked 316 specimens has been observed. However, as yet, copious swelling had not occurred in the 20% cold worked material. Specimens of 20% cold worked 316 fabricated from the same heat of material as those described above have now been irradiated to sufficiently high neutron fluences that swelling has occurred in both the annealed and cold worked conditions. The specimens were 2.5 cm long, biaxially pressurized tubes, with an OD of 0.58 cm and ID of 0.51 cm. Stress levels ranged from 0 to approximately 400 MPa. Specimens were irradiated in EBR-II to maximum fluences approximately 53 dpa. Swelling in the specimens was evaluated by pre- and post-irradiation immersion density measurements

1977-08-19

383

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-02-15

384

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

International Nuclear Information System (INIS)

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

2014-02-15

385

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

Science.gov (United States)

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

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

2014-02-01

386

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

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

387

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

International Nuclear Information System (INIS)

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

2012-12-15

388

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

2012-04-01

389

Tailoring the optical properties of epitaxially grown biaxial ZnO/Ge, and coaxial ZnO/Ge/Zno and Ge/ZnO/Ge heterostructures  

Energy Technology Data Exchange (ETDEWEB)

Heterostructures of epitaxially grown biaxial ZnO/Ge, and coaxial ZnO/Ge/ZnO and Ge/ZnO/Ge heterostructured nanowires with ideal epitaxial interfaces between the semiconductor ZnO sublayer and the Ge sublayer have been fabricated via a two-stage chemical vapor-solid process. Structural characterization by high-resolution transmission electron microscopy and electron diffraction indicates that both the ZnO and Ge sublayers in the heterostructures are single crystalline. A good epitaxial relationship of (100){sub ZnO} parallel (2 anti 20){sub Ge} exists at the interface between ZnO and Ge in the ZnO/Ge biaxial heterostructure. There is also an epitaxial relationship of (0 anti 10){sub ZnO} parallel (020){sub Ge} at the interface between the ZnO and Ge substructures in the coaxial ZnO/Ge/ZnO heterostructures, and a good epitaxial relationship of (0 anti 10){sub ZnO} parallel (0 anti 20){sub Ge} at the interface between ZnO and Ge in the Ge/ZnO/Ge coaxial heterostructure. Structural models for the crystallographic relationship between the wurtzite-ZnO and diamond-like cubic-Ge subcomponents in the heterostructures are given. The optical properties for the synthesized heterostructures are studied by spatially resolved cathodoluminescence spectra at low temperature (20 K). Excitingly, the unique biaxial and coaxial heterostructures display unique new luminescence properties. It is concluded that the ideal epitaxial interface between ZnO and Ge in the prepared heterostructures induces new optical properties. The group II-VI Ge-based nanometer-scale heterostructures and their interesting optical properties may inspire great interest in exploring related epitaxial heterostructures and their potential applications in lasers, gas sensors, solar energy conversion, and nanodevices in the future. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

Yin, L.W. [School of Materials Science and Engineering, Shandong University, Jinan 250061 (China); Advanced Materials Laboratory, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044 (Japan); Li, M.S. [School of Materials Science and Engineering, Shandong University, Jinan 250061 (China); Bando, Y.; Golberg, D.; Yuan, X.L.; Sekiguchi, T. [Advanced Materials Laboratory, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044 (Japan)

2007-01-22

390

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 ...

391

Managing Stress  

Medline Plus

Full Text Available ... when it makes us deal constructively with daily problems and meet the challenges. Stress has negative effects ... to high blood pressure, which can cause heart problems including heart attacks. Stress can also lead to ...

392

Managing Stress  

Medline Plus

Full Text Available ... attacks. Stress can also lead to migraine headaches, back pain and ulcers. Several studies have associated stress with ... healthcare professional or a recommendation for any particular treatment plan. Like any printed material, it may become ...

393

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. ...

394

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 ...

395

Managing Stress  

Medline Plus

Full Text Available ... 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 ...

396

Managing Stress  

Medline Plus

Full Text Available ... in control, you are setting yourself up for failure and more stress. Reward yourself. Treat yourself as ... stress can lead to serious diseases such as heart disease and depression. It may also lead to ...

397

An effective uniaxial tensile stress-strain relationship for prestressed concrete  

International Nuclear Information System (INIS)

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

1979-01-01

398

Magnetic properties of a mixed spin-1/2 and spin-3/2 Ising model with an uniaxial and biaxial crystal-field potential  

CERN Document Server

Magnetic properties of a mixed spin-1/2 and spin-3/2 Ising model on honeycomb lattice are investigated within the framework of an exact star-triangle mapping transformation. The particular attention is focused on the effect of uniaxial and biaxial crystal-field potentials that basically influence the magnetic behaviour of the spin-3/2 atoms. Our results for the basic thermodynamic quantities, as well as the dynamical time-dependent autocorrelation function indicate the spin tunneling between the $| \\pm \\frac32>$ and $| \\mp \\frac12>$ states in two different magnetically ordered phases OP$_1$ and OP$_2$, respectively.

Jascur, M; Jascur, Michal; Strecka, Jozef

2004-01-01

399

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

400

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

 
 
 
 
401

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

International Nuclear Information System (INIS)

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

1988-01-01

402

Tests on vitrinite reflectance of coal and analysis of tectonic stress field  

Energy Technology Data Exchange (ETDEWEB)

In order to deduce the tectonic stress field in North Henan by coal vitrinite reflectance, based on the principle that the tectonic stress is the main controlling factor of the vitrinite reflectance anisotropy (VRA), we have performed tests of coal vitrinite reflectance under microscope for directional coal specimen collected from Jiaozuo, Anyang, Hebi mining field in Henan province, and gained vitrinite reflectance ellipsoids (VRI) made up of reflectance maximum, reflectance middle value and reflectance minimum through some calculation to testing data. The results show that coal specimen in studied area indicate indicatrix of optical biaxial crystal, which suffered from intense tectonic deformation and the vitrinite reflectance anisotropy (VRA) is induced by tectonic stress. The tectonic stress field of North Henan obtained from vitrinite reflectance ellipsoids (VRI) is accordant basically with the tectonic stress field acquired from other methods, such as drilling, joint statistics and Henan province territorial tectonic stress field analysis, but there is small difference that the tectonic stress field has left deflexion in Anyang and Hebi. In short, the method deducing tectonic stress field by vitrinite reflectance anisotropy (VRA) is feasible and effective.

Jiang, J.P.; Gao, G.Y.; Kang, J.W. [Shanghai Maritime University, Shanghai (China)

2007-01-15

403

Bone Stress  

Science.gov (United States)

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

Exploratorium, The

2011-12-07

404

Biaxial Negative Indicatrix Movie  

Science.gov (United States)

This is a movie showing slices through crystals in different crystallographic orientations, and the corresponding indicatrix and interference colors. This is a big file and takes awhile to download. Make sure you have a current version of QuickTime to view it. The frame rate is fairly high so you might need to pause the movie and step through with the cursor keys during teaching.

Hirsch, David; University, Western W.

405

Managing Stress  

Medline Plus

Full Text Available ... is part of everyone’s life. If not managed, stress can lead to serious diseases such as heart disease and depression. It may also lead to drug and alcohol abuse. Preventing stress is easy with some changes in lifestyle and ...

406

Managing Stress  

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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 ...

407

Nuclear stress test  

Science.gov (United States)

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

408

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-05-01

409

Phase-modulated spectroscopic ellipsometry and polarized transmission intensity studies of wide-gap biaxial CaGa2S4  

International Nuclear Information System (INIS)

Differently prepared natural (100)-oriented cleavage planes of the orthorhombic wide-gap (Eo?4.1 eV) single crystalline CaGa2S4 were examined in two symmetric positions at room temperature over the photon energies 0.8-6.5 eV by spectroscopic ellipsometry. Complimentary, polarized transmission intensity technique was applied. The data obtained by both techniques were further treated within standard biaxial approach and the major refraction indices were restored for the practically important range below energy gap. The structure and polarization peculiarities of the obtained pseudo-dielectric function were related with apparently four critical points of interband electronic transitions in ZZ (E1=4.49 eV, E3=5.34 eV) and YY (E2=5.00 eV, E4=6.21 eV) configurations, respectively

2004-05-01

410

Structural and magnetic properties of biaxially textured NiFe2O4 thin films grown on c-plane sapphire  

Science.gov (United States)

Chemical solution deposition is used to grow biaxially textured NiFe2O4 (NFO) thin films on (0001) sapphire substrates; a high degree of out-of-plane orientation in the direction is confirmed by ?-2? X-ray diffraction and pole figures. X-ray J-scanning indicates in-plane texture and an epitaxial relationship between NFO (111) and Al2O3 (0001) in two crystallographic variants. The out-of-plane magnetization exhibits improved Mr/Ms from 0.5 in 110 nm-thick films to 0.8 in 60 nm-thick films. Compared to uniaxially textured NFO films on platinized silicon, the out-of-plane coercivity is reduced by 20%. The improved out-of-plane magnetic anisotropy is comparable to epitaxial NFO films of similar thickness deposited by pulsed laser deposition and sputtering.

Seifikar, Safoura; Calandro, Bridget; Deeb, Elisabeth; Sachet, Edward; Yang, Jijin; Maria, Jon-Paul; Bassiri-Gharb, Nazanin; Schwartz, Justin

2012-12-01

411

Effect of CeO2 cap layers on the preparation of YBCO films on rolling-assisted biaxially textured substrates by pulsed laser deposition  

Science.gov (United States)

YBCO films were grown on CeO2/YSZ/CeO2 buffered rolling-assisted biaxially textured substrates (RABiTS) by pulsed lased deposition (PLD). CeO2 cap layer was deposited prior to YBCO growth. CeO2 cap layers of different thickness were prepared to evaluate the thickness dependence of the YBCO films. The microstructure and surface morphology of the films were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that the thickness of the cap layer can remarkably affect the preparation of the subsequent YBCO layer. The possible mechanisms responsible for the dependence of the structure and the preparation of the YBCO films on the thickness of the CeO2 cap layers are discussed.

Liu, Linfei; Li, Yijie; Liu, Huaran; Song, Xiaokun; Hong, Dan; Wang, Ying; Xu, Da; Zhu, Shengping

2010-10-01

412

Epitaxial YBa_2Cu_3O_7 on biaxially textured (001) Ni: An approach to high critical current density superconducting tapes  

International Nuclear Information System (INIS)

In-plane aligned, c-axis oriented YBa_2Cu_3O_7 (YBCO) films with superconducting critical current densities, J_c, as high as 700,000 amperes per square centimeter at 77 kelvin have been grown on thermo-mechanically, rolled-textured (001) Ni tapes using pulsed-laser deposition. Epitaxial growth of oxide buffer layers directly on biaxially textured Ni, formed by recrystallization of cold-rolled pure Ni, enables the growth of 1.5 micrometer-thick YBCO films with superconducting properties that are comparable to those observed for epitaxial films on single crystal oxide substrates. This result represents a viable approach for producing long-length superconducting tapes for high current, high field applications at 77 kelvin

1997-06-15

413

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

Science.gov (United States)

We describe the full characterization of the biaxial nonlinear crystal BiB?O? (BiBO) as a polarization entangled photon source using non-collinear type-II parametric down-conversion. We consider the relevant parameters for crystal design, such as cutting angles, polarization of the photons, effective nonlinearity, spatial and temporal walk-offs, crystal thickness and the effect of the pump laser bandwidth. Experimental results showing entanglement generation with high rates and a comparison to the well investigated ?-BaB?O? (BBO) crystal are presented as well. Changing the down-conversion crystal of a polarization entangled photon source from BBO to BiBO enhances the generation rate as if the pump power was increased by 2.5 times. Such an improvement is currently required for the generation of multiphoton entangled states. PMID:21997051

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

2011-10-10

414

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

Science.gov (United States)

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

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

2010-01-01

415

Managing Stress  

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Full Text Available ... feelings cause changes in behavior such as snapping at others, having accidents, and compulsively tapping fingers. All ... that make you feel stressed? Feeling overwhelmed, either at work or at home, makes a lot of ...

416

Managing Stress  

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Full Text Available ... relax slowly and feel the difference. Relax with stretching and exercising. Stretching the muscles is another normal way for the body to react to stress. Stretching exercises can be done anywhere and anytime. If ...

417

Stress hyperglycaemia.  

Science.gov (United States)

Results of randomised controlled trials of tight glycaemic control in hospital inpatients might vary with population and disease state. Individualised therapy for different hospital inpatient populations and identification of patients at risk of hyperglycaemia might be needed. One risk factor that has received much attention is the presence of pre-existing diabetes. So-called stress hyperglycaemia is usually defined as hyperglycaemia resolving spontaneously after dissipation of acute illness. The term generally refers to patients without known diabetes, although patients with diabetes might also develop stress hyperglycaemia-a fact overlooked in many studies comparing hospital inpatients with or without diabetes. Investigators of several studies have suggested that patients with stress hyperglycaemia are at higher risk of adverse consequences than are those with pre-existing diabetes. We describe classification of stress hyperglycaemia, mechanisms of harm, and management strategies. PMID:19465235

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

2009-05-23

418

Managing Stress  

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Full Text Available ... as negative ones. Examples of positive events are marriage, graduation, starting a business, or the birth of ... problems include stressful situations such as an unhappy marriage, unstable job, poor relationship with a family member ...

419

Managing Stress  

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Full Text Available ... to recover physically and for the person to feel emotionally rewarded for overcoming the challenge. This document ... hands. • Fatigue. • Insomnia. • Heartburn. Stressed people may also feel: • Nervous. • Fearful. • Confused. • Worried. • Irritable. • Hostile. • Unable to ...

420

Managing Stress  

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Full Text Available ... the person becomes addicted. Symptoms and Causes