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- 주제어 : strain sweep (검색결과 6 건)
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장갑식,안혜진,송기원,Chang, Gap-Shik,Ahn, Hye-Jin,Song, Ki-Won The Korean Fiber Society 2015 한국섬유공학회지 Vol.52 No.3
Using an Advanced Rheometric Expansion System (ARES), the dynamic viscoelastic behavior of aqueous poly(ethylene oxide) (PEO) solutions with various molecular weights and different concentrations has been investigated in large amplitude oscillatory shear (LAOS) flow fields over a wide range of strain amplitudes. In order to predict the nonlinear viscoelastic behavior of polymer liquids in strain-sweep experiments, a new analysis method including a simple empirical model was proposed and then its validity was thoroughly evaluated in this study. The results have shown that the suggested model is significant in 95% confidence level and predicts exactly the nonlinear viscoelastic behavior of polymer liquids over a whole range of strain amplitudes tested. The strain limits of linear viscoelastic response and nonlinear behavior indices were determined using this model to estimate the LAOS flow behavior in strain-sweep experiments. The master curves of strain limits and nonlinear behavior indices can be obtained by representing these data against the product of angular frequency by characteristic time. The LAOS flow behavior of polymer systems with various molecular weights and different concentrations can well be predicted from these master curves.
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Dynamic fiber Bragg grating strain sensor interrogation with real-time measurement
Park, J.,Kwon, Y.S.,Ko, M.O.,Jeon, M.Y. Academic Press 2017 Optical fiber technology Vol.38 No.-
We demonstrate a 1550nm band resonance Fourier-domain mode-locked (FDML) fiber laser with fiber Bragg grating (FBG) array. Using the FDML fiber laser, we successfully demonstrate real-time monitoring of dynamic FBG strain sensor interrogation for structural health monitoring. The resonance FDML fiber laser consists of six multiplexed FBGs, which are arranged in series with delay fiber lengths. It is operated by driving the fiber Fabry-Perot tunable filter (FFP-TF) with a sinusoidal waveform at a frequency corresponding to the round-trip time of the laser cavity. Each FBG forms a laser cavity independently in the FDML fiber laser because the light travels different length for each FBG. The very closely positioned two FBGs in a pair are operated simultaneously with a frequency in the FDML fiber laser. The spatial positions of the sensing pair can be distinguished from the variation of the applied frequency to the FFP-TF. One of the FBGs in the pair is used asa reference signal and the other one is fixed on the piezoelectric transducer stack to apply the dynamic strain. We successfully achieve real-time measurement of the abrupt change of the frequencies applied to the FBG without any signal processing delay. The real-time monitoring system is displayed simultaneously on the monitor for the variation of the two peaks, the modulation interval of the two peaks, and their fast Fourier transform spectrum. The frequency resolution of the dynamic variation could reach up to 0.5Hz for 2s integration time. It depends on the integration time to measure the dynamic variation. We believe that the real-time monitoring system will have a potential application for structural health monitoring.
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파장 선형 스위핑 레이저를 이용한 광섬유 격자 센서의 스트레인 측정
엄진섭 ( Jinseob Eom ) 한국센서학회 2021 센서학회지 Vol.30 No.6
In this study, linearized sweeping of a wavelength sweeping laser was realized. This technique was used to measure the strain on a fiber Bragg grating(FBG) sensor. For linear sweeping, PID control over the wavelength difference between linear and nonlinear sweeping was employed. The performance test showed that linear sweeping with a 46 nm range and a 1 kHz frequency held up well with a 99.5% decrement in nonlinearity after the 120th feedback. When attached to a strain gage, the FBG sensor registered strain that matched the data sheet within a difference of 4.5[με]. Altogether, linear sweeping can play a leading role in monitoring a safety of large SOC structures as well as in other wavelength sweeping laser related fields.
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Flexural Vibration Analysis of a Sandwich Beam Specimen with a Partially Inserted Viscoelastic Layer
Park, Jin-Tack,Park, Nak-Sam The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.3
The flexural vibration characteristics of a sandwich beam system with a partially inserted viscoelastic layer were quantitatively studied using the finite element analysis in combination with the sine-sweep experiment. Asymmetric mode shapes of the flexural vibration were visualized by holographic interferometry, which agreed with those obtained by the finite element simulation. Effects of the length and the thickness of the partial viscoelastic layer on the system loss factor (η$\_$s/) and resonant frequency (f$\_$r/) were significantly large for both the symmetric and asymmetric modes of the beam system.
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개질된 폐타이어 분말을 이용한 열가소성 폴리우레탄의 물성 개선
강신혜(Shin Hye Kang),오지환(Ji-Hwan Oh),리시앙수(Xiangxu Li),조을룡(Ur Ryong Cho) 한국고분자학회 2017 폴리머 Vol.41 No.4
열가소성 폴리우레탄(thermoplastic polyurethane, TPU)이 가지는 경제적, 환경적 문제를 해결함과 동시에 TPU 물성 개선을 위한 방안으로 TPU에 폐타이어 분말을 적용하였다. 사용된 폐타이어(waste tire rubber, WTR)는 폐타이어를 변안활성기계(metactivator)에 통과시킨 것으로, 열역학적으로 불안정하며 미세 균열 입자의 형태를 보이고, 가교결합은 끊어진 상태로 존재한다. 단순히 TPU와 WTR을 혼합한 복합체와 2-hydroxyethyl methacrylate와 dicumyl peroxide를 사용하여 가교를 형성시킨 복합체를 제조하였다. WTR의 구조를 FTIR로 관찰하고, TPU와 두 종류의 TPU/WTR 복합체를 DSC를 통해 유리전이온도(Tg)를 측정하였다. 가교로 개질된 TPU/WTR 복합체는 내수성, 내화학성이 크게 향상되었고, 극성 비양성자성 용매에서의 팽윤 특성 또한 우수하였다. 또한 저장탄성률의 증가와 함께 영구압축 줄음률 또한 크게 향상되었다. To solve the economic and environmental problems of thermoplastic polyurethane (TPU), waste tire powder (WTR) was applied to improve the physical properties of TPU. The waste tire rubber is a waste tire that has passed through a metactivator and is thermodynamically unstable, showing the shape of microcracked particles, and the crosslinking is broken. The composites were prepared by simply mixing of TPU and WTR and a crosslinking agent using 2- hydroxyethyl methacrylate and dicumyl peroxide. The structure of WTR was observed by FTIR, and the glass transition temperature (Tg) of TPU and two kinds of TPU/WTR composites were measured by DSC. The modified TPU/WTR composites showed significant improvements in water resistance, chemical resistance, and swelling properties in polar aprotic solvents. As the storage modulus increased, the compression set was also remarkably improved.
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