Function Of Axial Strain Research Articles

The effect of enzymatic GAG degradation on transverse shear properties of porcine cornea

The structural integrity of cornea depends on properties of its extracellular matrix, mainly a mixture of collagen fibers and soluble proteoglycans (PGs). PGs are macromolecules of negatively charged sulphated glycosaminoglycans (GAGs) covalently attached to a protein core. GAGs appear as bridges between adjacent collagen fibers and could facilitate force transfer between them. Furthermore, GAGs are responsible for corneal hydration by attracting and maintaining water molecules into the extracellular matrix. Based on these observations, GAGs are expected to be essential for biomechanical properties of cornea. The primary objective of the present study was to determine the effects of GAGs on shear properties of cornea. For this purpose, GAGs were enzymatically removed from porcine corneal disks by keratanase II enzyme. After confirming the successful removal of GAGs by histochemical methods, torsional rheometry was performed to characterize the shear stiffness of GAG-depleted samples as a function of axial strain. It was found that the shear modulus of all samples was a function of applied shear strain and compressive strain. Beyond the range of linear viscoelastic response, the average complex shear modulus decreased with increasing the shear strain. Increasing the axial strain from 0% to 40% significantly increased the average complex shear modulus of corneal disks in all groups. Finally, the enzyme treatment with keratanase II enzyme significantly decreased the shear stiffness. The experimental measurements were discussed in terms of microstructural and compositional properties of corneal extracellular matrix and it was concluded that GAGs play a significant role in defining shear properties of cornea.

Cyclic behaviour of CFRP confined concrete under axial compression

This research aims to experimentally investigate the cyclic behaviour of externally strengthened concrete with carbon fibre reinforced polymer composites (CFRP). This paper presents the results of monotonic cyclic compression tests conducted on 17specimens – 9 cylindrical and 8 prismatic – with identical slenderness ratios of 2. The transverse cross-sectional shape and the confinement rate were the main test variables. The experimental results are presented as axial stress-axial strain cyclic responses.When compared to existing results in the literature, the envelope curves obtained show almost identical behaviours, confirming that confinement has a positive effect on strength and deformability. Such confinement is more effective in cylindrical specimens than prismatic ones.After analysing of the cyclic responses, the influence of varying the confinement rate on the cyclic parameters was investigated. Polynomial correlations of the secant stiffness and the plastic strain as a function of axial strain were highlighted.The results show that for both geometric shapes, the residual strain andstiffness degradation are independent of the confinement rate. Contrarily to the dissipated and restored energies, which are significantly affected by increasing number of CFRP layers.The results also indicate that the variation of the dissipated energy, restored energy and damage capacity consists of two successive phases; the first corresponds to the pre-peak phase where the responses are almost confused, followed by a second phase which corresponds to the post-peak phase where the responses are dispersed.

Properties of Toroidal Field Nb3Sn Strands Made for the ITER Chinese Domestic Agency

China was responsible for supplying 7.5% of ITER toroidal field (TF) Nb 3 Sn conductors. It has delivered all the required conductors unit lengths and fulfilled the TF conductor package. The conductor package delivery consisted of four phases, in terms of phase I (call for tender), II (qualification process), III (pre-production process), and IV (production process). This paper focuses on work from phases II to IV. The Superconducting Strand Test Laboratory of the Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) was the reference laboratory of the Chinese Domestic Agency and undertook the task of Nb 3 Sn strands verification based on the requirements of ITER procurement arrangements. The verification results showed that the strands properties fulfill ITER specifications. In addition, in order to know well the strand properties and supply essential data for conductors' performance prediction and analysis, the mechanical properties and critical current Ic as a function of axial strain, temperature, and magnetic field for the TF strands have been tested and summarized.

Theoretical model for concrete-filled stainless steel circular stub columns under axial compression

Experimental studies on concrete-filled stainless steel (SS) circular stub columns (in the form of fully filled and double-skin) have been reported in the last 10 years, but there is still a lack of theoretical model to predict the complete load-axial strain curve of such stub columns under axial compression. This study presents a load-axial strain model for concrete-filled SS tubes, which takes account of the interaction between the encasing tube and concrete core. A dilation model is first proposed in which the dilation rate is expressed as a function of axial strain and outer tube diameter-to-thickness ratio. The theory of metal plasticity in the form of deformation type is adopted to calculate the bi-axial stresses in the SS outer tube. The SS inner tube is assumed to be under uni-axial compression and continuous strength method (CSM), which is suitable for strain hardening material such as SS, is adopted. The effect of SS tube buckling on reducing the axial stress and confining stress is considered in the model. Numerical procedures are proposed to generate the complete load-axial strain curve which involve an incremental process. Finally, the predicted load-axial strain curves are compared with the experimental results obtained by the authors and other researchers, and a good agreement is achieved.

Numerical studies of electrical contacts of carbon nanotubes-embedded epoxy under tensile loading

Numerical studies were performed to determine electrical contacts in carbon nanotubes (CNTs)-embedded epoxy under quasi-static tensile loading conditions. A realistic CNT network in epoxy was generated by random orientation and waviness by employing the Monte Carlo method. Two kinds of contacts between CNTs, namely Type-I (overlap) and Type-II (in-plane), were considered in generating a conductive network. A commercial finite element package, COMSOL, was used to determine the distance between these contacts and variation of these contacts during elastic deformation under tensile loading. Numerical predictions were later compared with the analytical results derived from experimental findings. The effect of initial f-ratio and the amount of waviness of CNTs on the variation of f-ratio (which is determined as a ratio of Type-II contacts to total contacts) was investigated as a function of axial strain. The initial f-ratio as well as the extent of waviness showed a significant effect on the change in the type of contacts with increasing axial strain values.

Critical current of dense Bi-2212 round wires as a function of axial strain

The critical current (Ic) of dense Bi2Sr2CaCu2O8+x (Bi-2212) round wires with Ag-alloy matrices was measured as a function of axial applied strain (), to determine whether the behavior is improved in comparison to wires with a large (30–50%) void fraction in the Bi-2212 filaments. Wires were reacted at approximately under a 1% O2 in Ar gas mixture at 100 bar pressure to densify the Bi-2212 fraction during the partial melt reaction. After measurement of the Ic at 4.2 K and 5 T at Florida State University, wire sections were sent to Lawrence Berkeley National Laboratory where was measured at 4.2 K at 5 and 15 T using a U-shaped bending spring. We found that has a 0.3% wide linear reversible strain range. An unexpected result is that the width of this reversible range seems comparable to that found for porous samples reacted at only 1 bar, apparently negating an earlier plausible supposition that fuller density samples would be more resilient.

Versatile poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) films on polydimethylsiloxane substrates having random micro ridges: Study of resistive behaviors of a polymer–polymer laminate

ABSTRACTConductive polymers such as poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) or PEDOT:PSS has become increasingly important in present day organic electronics. PEDOT:PSS being a polymer is more durable than metals used in electronics and thus offers greater mechanical flexibility during operation. This article presents results regarding resistive behaviors of blade coated PEDOT:PSS films on polydimethylsiloxane (PDMS) substrate having random micro ridges as a function of axial strain and different temperatures. The average resistance of the blade coated PEDOT:PSS films were found to increase by 1.4 times between 35 and 45% axial strain. The resistances of the films were found to change within the temperature range of 25–230°C without any thermal morphological degradations and the polymer–polymer laminate also showed linear thermal actuation behavior. These results suggest that the blade coated PEDOT:PSS films on PDMS substrates with random micro ridges can be potentially useful in versatile applications like stretchable conductors, thermal actuators, thermoelectric generators, and as heating surfaces. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41235.

In situ multiproperty measurements of individual nanomaterials in SEM and correlation with their atomic structures

The relationship between property and structure is one of the most important fundamental questions in the field of nanomaterials and nanodevices. Understanding the multiproperties of a given nano-object also aids in the development of novel nanomaterials and nanodevices. In this paper, we develop for the first time a comprehensive platform for in situ multiproperty measurements of individual nanomaterials using a scanning electron microscope (SEM). Mechanical, electrical, electromechanical, optical, and photoelectronic properties of individual nanomaterials, with lengths that range from less than 200 nm to 20 μm, can be measured in situ with an SEM on the platform under precisely controlled single-axial strain and environment. An individual single-walled carbon nanotube (SWCNT) was measured on the platform. Three-terminal electronic measurements in a field effect transistor structure showed that the SWCNT was semiconducting and agreed with the structure characterization by transmission electron microscopy after the in situ measurements. Importantly, we observed a bandgap increase of this SWCNT with increasing axial strain, and for the first time, the experimental results quantitatively agree with theoretical predictions calculated using the chirality of the SWCNT. The vibration performance of the SWCNT, a double-walled CNT, and a triple-walled CNT were also studied as a function of axial strain, and were proved to be in good agreement with classical beam theory, although the CNTs only have one, two, or three atomic layers, respectively. Our platform has wide applications in correlating multiproperties of the same individual nanostructures with their atomic structures.

Intrawire resistance, AC loss and strain dependence of critical current in MgB2 wires with and without cold high-pressure densification

The intrawire resistance and alternating current (AC) loss of two MgB2 wires with filaments surrounded by Nb barriers have been measured and analyzed. Relatively high values of filament-to-matrix contact resistivity are found in the MgB2 wires; the values are two or three orders higher than those commonly found in NbTi or Nb3Sn wires. Considering the high porosity of the MgB2 filaments, cold high-pressure densification has been applied on the two MgB2 wires to investigate its impact on intrawire resistance and AC loss. The intrawire resistance is measured with a direct four-probe voltage-current method at various temperatures. The AC loss is measured by vibrating sample magnetometer measurements at 4.2 K. In addition to the intrawire resistance measurements, the critical current of MgB2 wires before and after densification is measured with a U-shaped bending spring at 4.2 K as function of axial strain. The critical current in densified MgB2 wires is found to be higher than that in the same wire without densification; it is also less sensitive to the applied axial strain.

The Secant Method for Buckling Load of Centrally Compressed Member with Residual Stresses

A fast method for elastic-plastic buckling of centrally compressed members is put forward, which is suitable for the medium length column considering the effect of residual stresses. The problem of elastic-plastic buckling is simplified as a nonlinear function of axial strain, and the secant algorithm is built based on the nonlinear function. The advantages of the new method are discussed and the iterative calculation process is listed. The new method offers significant improvements in accuracy, robustness and calculation amount of the solution, which can be used for members with any type section. An example of I-shape member is calculated by the new method and the result is compared with the analytical solution. The contrast of the buckling load verifies the reliability of the new method.

Strain and Magnetic-Field Characterization of a Bronze-Route ${\rm Nb}_{3}{\rm Sn}$ ITER Wire: Benchmarking of Strain Measurement Facilities at NIST and University of Twente

A benchmarking experiment was conducted to compare strain measurement facilities at the National Institute of Standards and Technology (NIST) and the University of Twente. The critical current of a bronze-route Nb3Sn wire, which was fabricated for the International Thermonuclear Experimental Reactor (ITER), was measured as a function of axial strain and magnetic field in liquid helium at both institutes. NIST used a Walters' spring strain device and University of Twente used a bending beam (“Pacman”) apparatus. The ITER bronze-route wire investigated had a very high irreversible strain limit that allowed comparing data over a wide range of applied strain between -1% and +1%. Similarities of the data obtained by use of the two apparatuses were remarkable, despite the many differences in their design and techniques.

Characterization of $\hbox{Nb}_{3}\hbox{Sn}$ Strands for a 40-T Hybrid Magnetic Model Coil

A 40-T hybrid magnet under construction at the High Magnetic Field Laboratory of the Chinese Academy of Sciences will use cable-in-conduit conductors for its superconducting outsert. The design necessitates the use of high current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ≥ 2100 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 12 T/4.2 K). The high J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> restacked-rod-processed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand from Oxford Instruments Superconductor Technology was selected as one of the candidate strands. A series of tests was carried out to qualify the strand performance. Tests mainly included magnetization and critical current measurements as a function of axial strain, magnetic fields, and temperature. The test results are presented and discussed.

The $I_{C}$ Irreversible Strain of Some ITER High $J_{C}$${\rm Nb}_{3}{\rm Sn}$ Wires

ITER high J C Nb3Sn wires are designed to compensate for the performance degradation due to transverse electromagnetic force in cable-in-conduit-conductor. J C characterization of these wires, especially as a function of axial strain, is very important. We performed I C irreversibility strain epsivirr-epsivmax measurements and geometry examinations on two types of ITER high J C Nb3Sn wires. epsivirr-epsivmax is measured in a 18 T magnetic field by a straight pull device developed at the NHMFL. Consistent difference in epsivirr between the two types of strands is observed. We found that the epsivirr-epsivmax is ~ 0.3% for the type of strands with higher J C and ~ 0.4% for that with lower J C . This can be correlated to the difference in their geometry.

Permeability evolution during progressive development of deformation bands in porous sandstones

Triaxial deformation experiments were carried out on large (0.1 m) diameter cores of a porous sandstone in order to investigate the evolution of bulk sample permeability as a function of axial strain and effective confining pressure. The log permeability of each sample evolved via three stages: (1) a linear decrease prior to sample failure associated with poroelastic compaction, (2) a transient increase associated with dynamic stress drop, and (3) a systematic quasi‐static decrease associated with progressive formation of new deformation bands with increasing inelastic axial strain. A quantitative model for permeability evolution with increasing inelastic axial strain is used to analyze the permeability data in the postfailure stage. The model explicitly accounts for the observed fault zone geometry, allowing the permeability of individual deformation bands to be estimated from measured bulk parameters. In a test of the model for Clashach sandstone, the parameters vary systematically with confining pressure and define a simple constitutive rule for bulk permeability of the sample as a function of inelastic axial strain and effective confining pressure. The parameters may thus be useful in predicting fault permeability and sealing potential as a function of burial depth and fault displacement.

Descriptive model for the critical current as a function of axial strain in Bi-2212/Ag wires

A descriptive model is presented for the critical current of a Bi-2212 conductor that is axially deformed. This model is based on previously published critical current measurements on axially compressed and elongated Bi-2212 wires. The validity of the model is investigated by applying an additional pre-strain at room temperature. The experimental results on the pre-strained wires are in reasonable agreement with the prediction. The description for the critical-current reduction in Bi-2212 is applied in a model for a bend conductor. This model predicts the critical current as a function of the bending radius in a wire and a tape conductor.

The influence of compressive and tensile axial strain on the critical properties of Nb/sub 3/Sn conductors

Various Nb/sub 3/Sn conductors are investigated in an axial strain experiment. The superconducting samples are soldered to a substrate that is bent to generate a compressive or tensile axial strain. Especially in the compressive strain range the critical current reduction is smaller than predicted by the well-known scaling law. The influence of the transverse strain components is investigated in a tape conductor by changing the thermal strain. It is found that the axial strain experiments can be described by an upper-critical field that depends on the deviatoric component of the strain tensor only. Finally a comparison of the critical temperature and the critical current as a function of axial strain is made. >