• Title/Summary/Keyword: Electromechanical strain

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Influence of brass laminate volume fraction on electromechanical properties of externally laminated coated conductor tapes

  • Bautista, Zhierwinjay M.;Shin, Hyung-Seop;Lee, Jae-Hun;Lee, Hunju;Moon, Seung-Hyun
    • Progress in Superconductivity and Cryogenics
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    • v.18 no.3
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    • pp.6-9
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    • 2016
  • The enhancement of mechanical properties of coated conductor (CC) tapes in practical application are usually achieved by reinforcing through lamination or electroplating metal layers on either sides of the CC tape. Mechanical or electromechanical properties of the CC tapes have been largely affected by the lamination structure under various loading modes such as tension, bending or even cyclic. In this study, the influence of brass laminate volume fraction on electromechanical properties of RCE-DR processed Gadolinium-barium-copper-oxide (GdBCO) CC tapes was investigated. The samples used were composed of single-side and both-side laminate of brass layer to the Cu-stabilized CC tape and their $I_c$ behaviors were compared to those of the Cu-stabilized CC tape without external lamination. The stress/strain dependences of $I_c$ in laminated CC tapes under uniaxial tension were analyzed and the irreversible stress/strain limits were determined. As a result, the increase of brass laminate volume fraction initially increased the irreversible strain limit and became gradual. The corresponding irreversible stress limit, however, showed no difference even though the brass laminate volume fraction increased to 3.4. But the irreversible load limit linearly increased with the brass laminate volume fraction.

Characterization of electromechanical properties of Sn-Cu double layer stabilized GdBCO coated conductor tapes at 77 K

  • Shin, Hyung-Seop;Diaz, Mark Aangelo;Lee, Jae-Hun
    • Progress in Superconductivity and Cryogenics
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    • v.19 no.4
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    • pp.26-30
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    • 2017
  • The promising characteristics of 2G high-temperature superconductor (HTS) coated conductor (CC) tapes have made it possible to apply to various electrical device applications. In this study, the mechanical and electromechanical properties of Sn-Cu double layer stabilized GdBCO CC tapes have been characterized. The stress and strain tolerances of $I_c$ in GdBCO CC tapes adopting stainless steel substrate were evaluated using $I_c$-strain measurement at 77 K under both uniaxial tension and monotonic bending conditions. The results were compared to the conventional single Cu layer stabilized CC tape. As a result, the Sn-Cu double layer stabilized GdBCO CC tapes showed somehow lower or comparable electromechanical properties as compared to the Cu stabilized CC tape ones.

Establishment of strain measurement system for evaluation of strain effect in HTS tapes under magnetic field

  • Dedicatoria, Marlon J.;Shin, Hyung-Seop
    • Progress in Superconductivity and Cryogenics
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    • v.13 no.4
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    • pp.14-17
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    • 2011
  • The evaluation of the electromechanical properties of HTS CC tapes is one of the foremost procedures to be done to ensure the applicability of superconducting wires to electric devices. A precise measurement of the stress and strain is important in deriving the mechanical properties under operating environment. Up to now, there is no standard test method yet for the electromechanical property evaluation of HTS tapes under self field and external magnetic field although there are already reports on the different devices used to evaluate these properties. Strain can be measured by adopting a strain gauge or a high resolution double extensometer. In this study, strain effect on $I_c$ in HTS CC tapes under magnetic fields was evaluated. Comparison of advantages and setback of strain measuring devices were discussed. In addition, a dual strain measurement system using both the SG and extensometer may be practical to lessen the burden in case one of the measuring devices does not work well.

Measurement reliability of irreversible stress/strain limits in Sn-Cu double layer stabilized IBAD/RCE-DR processed GdBCO coated conductor tapes under uniaxial tension at 77 K

  • Bautista, Zhierwinjay;Diaz, Mark Angelo;Shin, Hyung-Seop;Lee, Jae-Hun
    • Progress in Superconductivity and Cryogenics
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    • v.20 no.4
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    • pp.36-40
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    • 2018
  • In this study, the electromechanical properties in Sn-Cu double layer stabilized GdBCO coated conductor (CC) tapes with and without external lamination under uniaxial tension were examined at 77 K and self-field. Their irreversible stress and strain limits were determined using a loading-unloading scheme based on different critical current ($I_c$) recovery criteria. The repeated tests were performed and statistical estimation was done to check the reproducibility depending on the criterion adopted in evaluating the electromechanical properties. From the results, it showed that the Sn-Cu double-layer stabilized CC tapes have the higher irreversible stress limit, but lower irreversible strain limit as compared to brass laminated ones. Through the repeated tests, it can be found that a small scattering of irreversible limits existed in both CC tape samples. Finally, similar strain sensitivity of $I_c$ in both CC tapes was obtained.

Effects of La2O3 Doping on Phase Transition Behavior and Electromechanical Strain Properties in Bismuth-Based Lead-Free Piezoelectric Ceramics (비스무스계 무연 압전 세라믹스의 상전이 거동 및 전기 기계적 변형 특성에 대한 La2O3 도핑 효과 연구)

  • Eun Seo Kang;Sung Jae Hyoung;Yubin Kang;Min Sung Park;Trang An Duong;Jae-Shin Lee;Hyoung-Su Han
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.37 no.4
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    • pp.457-463
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    • 2024
  • (Bi1/2Na1/2)TiO3(BNT) piezoelectric ceramics are one of the promising materials that can replace Pb(Zr, Ti)O3(PZT) piezoelectric ceramics due to the high electromechanical strain properties. However, it is still difficult to use practical applications because the required electric field for inducing electromechanical strain is relatively higher than that of PZT ceramics. To overcome this problem, it has been intensively studied on doping impurity or modifying other ABO3 for BNT-based piezoelectric ceramics. Therefore, this study investigated the effects of La2O3 doping on the phase transition behavior and electromechanical strain properties in BNT-SrTiO3 (BNT-ST) lead-free piezoelectric ceramics. In the case of the temperature-dependent dielectric properties, it was confirmed that a phase transition from ferroelectrics to relaxors is induced with increasing La2O3 content. As a result, the electromechanical strain properties of BNT-ST ceramics were improved. The highest Smax/Emax value corresponding to 300 pm/V was obtained at 2 mol% La2O3-dopped BNT-ST ceramics. Accordingly, this study successfully demonstrated that La2O3 doping is effective on the inducing phase transition from ferroelectrics to relaxors and the improving electromechanical strain properties of BNT-ST lead-free piezoelectric ceramics.

Size dependent torsional vibration of a rotationally restrained circular FG nanorod via strain gradient nonlocal elasticity

  • Busra Uzun;Omer Civalek;M. Ozgur Yayli
    • Advances in nano research
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    • v.16 no.2
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    • pp.175-186
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    • 2024
  • Dynamical behaviors of one-dimensional (1D) nano-sized structures are of great importance in nanotechnology applications. Therefore, the torsional dynamic response of functionally graded nanorods which could be used to model the nano electromechanical systems or micro electromechanical systems with torsional motion about the center of twist is examined based on the theory of strain gradient nonlocal elasticity in this work. The mathematical background is constructed based on both strain gradient theory and Eringen's nonlocal elasticity theory. The equation of motions and boundary conditions of radially functionally graded nanorods are derived using Hamilton's principle and then transformed into the eigenvalue analysis by using Fourier sine series. A general coefficient matrix is obtained to assemble the Stokes' transformation. The case of a restrained functionally graded nanorod embedded in two elastic springs against torsional rotation is then deeply investigated. The effect of changing the functionally graded index, the stiffness of elastic boundary conditions, the length scale parameter and nonlocal parameter are investigated in detail.

Effects of SrTiO3-Modification on the Dielectric and Electromechanical Strain Properties of Lead-Free Bi1/2Na1/2TiO3-BiAlO3 Piezoceramics (Bi1/2Na1/2TiO3-BiAlO3 무연 압전 세라믹스의 유전 및 전기 기계적 변형 특성에 대한 SrTiO3 첨가 효과)

  • Lee, Sang Sub;Lee, Chang-Heon;Duong, Trang An;Kim, Dong Hyeok;Kim, Byeong Woo;Han, Hyoung-Su;Lee, Jae-Shin
    • Korean Journal of Materials Research
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    • v.31 no.10
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    • pp.562-568
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    • 2021
  • (Bi1/2Na1/2)TiO3 (BNT)-based ceramics are considered promising candidates for actuator application owing to their excellent electromechanical strain properties However, to obtain large strain properties, there remain several issues such as thermal stability and high operating fields. Therefore, this study investigates a reduction of operating field in (0.98-x)Bi1/2Na1/2TiO3-0.02 BiAlO3-xSrTiO3 (BNT-2BA-100xST, x = 0.20, 0.21, 0.22, 0.23, and 0.24) via analyses of the microstructure, crystal structure, dielectric, polarization, ferroelectric and electromechanical strain properties. The average grain size of BNT-${\underline{2}}$BA-100xST ceramics decreases with increasing ST content. Results of polarization and electromechanical strain properties indicate that a ferroelectric to relaxor state transition is induced by ST modification. As a consequence, a large electromechanical strain of 592 pm/V is obtained at a relatively low electric field of 4 kV/mm in 22 mol% ST-modified BNT-2BA ceramics. We believe that the materials synthesized in this study are promising candidates for actuator applications.

The effect of mechanical inhomogeneity in microzones of welded joints on CTOD fracture toughness of nuclear thick-walled steel

  • Long Tan;Songyang Li;Liangyin Zhao;Lulu Wang;Xiuxiu Zhao
    • Nuclear Engineering and Technology
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    • v.55 no.11
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    • pp.4112-4119
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    • 2023
  • This study employs the microshear test method to examine the local mechanical properties of narrow-gap welded joints, revealing the mechanical inhomogeneity by evaluating the microshear strength, stress-strain curves, and failure strain. On this basis, the influence of weld joints micromechanical inhomogeneity on the crack tip opening displacement (CTOD) fracture toughness is investigated. From the root weld layer to the cover weld layer, the fracture toughness at the center of the weld seam demonstrates an increasing trend, with the experimental and calculated CTOD values showing a good correspondence. The microproperties of the welded joints significantly impact the load-bearing capacity and fracture toughness. During the deformation process of the "low-matching" microregions, the plastic zone expansion is hindered by the surrounding microregion strength constraints, thus reducing the fracture toughness. In contrast, during the deformation of the "high-matching" microregions, the surrounding microregions absorb some of the loading energy, partially releasing the concentrated stress at the crack tip, which in turn increases the fracture toughness.

A study on electromechanical properties of CNT conductive film deposited on flexible substrate (유연 모재 위에 증착된 CNT 전도성 필름의 전기-기계적 특성에 대한 연구)

  • Song, Sun-Ah;Kim, Jae-Hyun;Lee, Hak-Joo;Song, Jin-Woo;Chang, Won-Seok;Han, Chang-Soo
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.35-39
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    • 2008
  • In this study, electromechanical properties of carbon nanotube (CNT) thin film on flexible substrates were measured using a micro-tensile machine with functionality of simultaneous measurements of displacement, load and electrical resistance. The CNT thin film of about 100 nm thick was deposited on flexible substrates, polyethylene terephthalate (PET) using spraying and ink-jetting techniques. To investigate the effect of process condition on the electromechanical properties of CNT thin film, sets of CNT samples were fabricated under various heat treatments and microwave process. The microstructures of the CNT thin film before and after tensile test were investigated using Scanning Electron Microscope (SEM), and the failure modes of the CNT thin films were identified to understand their electromechanical behaviors and interaction with the flexible substrates. Based on the experimental results, the use of CNT thin film as flexible electrodes and strain gages is discussed.

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Approximate evaluations and simplified analyses of shear- mode piezoelectric modal effective electromechanical coupling

  • Benjeddou, Ayech
    • Advances in aircraft and spacecraft science
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    • v.2 no.3
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    • pp.275-302
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    • 2015
  • Theoretical and numerical assessments of approximate evaluations and simplified analyses of piezoelectric structures transverse shear modal effective electromechanical coupling coefficient (EMCC) are presented. Therefore, the latter is first introduced theoretically and its approximate evaluations are reviewed; then, three-dimensional (3D) and simplified two-dimensional (2D) plane-strain (PStrain) and plane-stress (PStress) piezoelectric constitutive behaviors of electroded shear piezoceramic patches are derived and corresponding expected short-circuit (SC) and open-circuit (OC) frequencies and resulting EMCC are discussed; next, using a piezoceramic shear sandwich beam cantilever typical benchmark, a 3D finite element (FE) assessment of different evaluation techniques of the shear modal effective EMCC is conducted, including the equipotential (EP) constraints effect; finally, 2D PStrain and PStress FE modal analyses under SC and OC electric conditions, are conducted and corresponding results (SC/OC frequencies and resulting effective EMCC) are compared to 3D ones. It is found that: (i) physical EP constraints reduce drastically the shear modal effective EMCC; (ii) PStress and PStrain results depend strongly on the filling foam stiffness, rendering inadequate the use of popular equivalent single layer models for the transverse shear-mode sandwich configuration; (iii) in contrary to results of piezoelectric shunted damping and energy harvesting popular single-degree-of-freedom-based models, transverse shear modal effective EMCC values are very small in particular for the first mode which is the common target of these applications.