• 제목/요약/키워드: Superposition Principle

검색결과 101건 처리시간 0.024초

시간-온도 중첩이론을 적용한 아스팔트 바인더의 점소성 구성 모형 (A Viscoplastic Constitutive Model Based on Overstress Concept with Time-Temperature Superposition Principle)

  • 윤태영;엄병식;유평준;김연복
    • 한국도로학회논문집
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    • 제14권5호
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    • pp.75-83
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    • 2012
  • PURPOSES: Suggestion of asphalt binder constitutive model based on time-temperature superposition principle and overstress concept in order to describe behavior of asphalt binders. METHODS: A series of temperature sweep tests and multiple stress creep and recovery(MSCR) tests are performed to verify the applicability of time-temperature superposition principle(t-Ts) and to develop viscoelastoplastic constitutive equation based on overstress concept. For the tests, temperature sweep tests at various high temperature and various frequency and MSCR test at $58^{\circ}C$, $64^{\circ}C$ $70^{\circ}C$, $76^{\circ}C$, and $82^{\circ}C$ are performed. From the temperature sweep tests, dynamic shear modulus mastercurve and time-temperature shift function are built and the shift function and MSCR at $58^{\circ}C$ are utilized to determine model coefficients of VBO model. RESULTS: It is observed that the time-temperature shift function built at low strain level of 0.1% is applicable not only to 1.0% strain level temperature sweep test but also maximum 500,00% strain level of MSCR test. As well, the modified VBO model shows perfect prediction on MSCR measured strain at the other temperatures. CONCLUSIONS: The Time-temperature superposition principle stands hold from very low strain level to very high strain level and that the modified VBO model can be applicable for various range of strain and temperature region to predict elastic, viscoelastic, and viscoplastic strain of asphalt binders.

중첩의 원리를 적용한 PC 베이스 영구자석 동기 전동기 센서리스제어 (A PC Based for PMSM Sensorless Control Using Superposition Theorem)

  • 이상훈;홍인표;박성준;김철우
    • 대한전기학회논문지:전기기기및에너지변환시스템부문B
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    • 제51권6호
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    • pp.292-297
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    • 2002
  • This paper proposes a sensorless drive of a permanent magnet synchronous motor. In general EMF is used to calculate the current of Permanet Magnet Synchronous Motor(PMSM). However the current has a lag component by a time constant. So it is difficult to directly calculate a position angle. To estimate the position using the current without a lag component in this paper, the controller calculates the motor current by using a superposition principle in the equivalent circuit and then compensates lag component with a time constant of the motor. Therefore the estimated motor current without a lag compoent can be obtained and it is used to calculate the rotor position indirectly. In order to confirm the effectiveness of the proposed algorithm, experimental results are shown in detail.

A Comparison of the Dielectric Behavior of Aromatic and Aliphatic Polyurethanes in Relation to Transitional Phenomena

  • Kim, Chy Hyung
    • Transactions on Electrical and Electronic Materials
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    • 제18권4호
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    • pp.211-216
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    • 2017
  • The dielectric properties of two polyurethanes (PUs) with different hard segments, i.e., aromatic methylene di-p-phenyl diisocyanate (MDI) and aliphatic hexamethylene diisocyanate (HDI), were investigated in the temperature range of -100 to $100^{\circ}C$ and in the frequency range of 1 Hz to 3 kHz. The ${\alpha}$-relaxations induced by the glass transition of the equivalent soft segments in the two PUs occurred at relaxation times of ${\tau}=3.46{\times}10^{-3}s$ for MDI-PU and ${\tau}=3.39{\times}10^{-2}s$ for HDI-PU at $-20^{\circ}C$, in accord with the temperature-frequency superposition principle, resulting in similar shifting factors. However, different I-relaxations were observed for the two PUs. The I-relaxation of MDI-PU occurred due to the mobility of the chain extenders near $80^{\circ}C$ with a slower shifting rate than the ${\alpha}$-relaxation. On the other hand, I-relaxation arising from both the extender and the unconstrained hard segments of HDI-PU occurred at $70{\sim}100^{\circ}C$, indicating complicated dielectric behavior due to partial interaction with the ${\alpha}$-relaxation at high frequencies. Thus, the I-relaxation of HDI-PU did not follow the superposition principle. The dielectric behaviors of the PUs were mainly influenced by their phase transitions, which were affected by the structure and components of the materials.

유한요소격자중첩을 이용한 복합재료평판의 변위 및 응력의 복원 (Local Response Recovery for Multilayered Composite Panels using Mesh Superposition)

  • 박진우;김용협
    • 한국복합재료학회:학술대회논문집
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    • 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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    • pp.89-92
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    • 2000
  • In this paper, an effective procedure is presented for the local recovery of displacements and stresses in multilayered composite panels, which incorporate the local refinement using mesh superposition. The mesh superposition method is used to refine the global coarse mesh by superimposing refined mesh to the localized zone of interest without transition zones. The finite element model used is a solid element based on the Hellinger-Reissner variational principle. The a posteriori computation of the through-the-thickness distributions of displacements and stresses is achieved using a predictor-corrector procedure. The procedure utilizes the superconvergent stresses and nodal displacements of the finite element patch. The element patch is generated by locally superimposing a refined local mesh to the coarse global mesh.

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Creep of concrete at variable stresses and heating

  • Klovanych, Sergei
    • Computers and Concrete
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    • 제16권6호
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    • pp.897-908
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    • 2015
  • This article gives analytical dependences for creep of concrete at heating, taking into account conditions of its drying. These dependences are based on the standard nonlinear theory of creep of concrete at a normal temperature and temperature-time analogy. For the description of creep at various stresses and temperatures the principle of superposition are used. All stages of model's creation are confirmed by the existing experimental data. Calculation examples are given.

리브 구조에 따른 머시닝센터 베드의 열적 특성 평가 (Thermal Characteristic Estimation of NC Machining Center Bed following Rib Structure)

  • 김양진
    • 한국생산제조학회지
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    • 제19권6호
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    • pp.746-752
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    • 2010
  • Rib structure has been used to bed and column of machine tool to heighten weight stiffness ratio, cost performance and weight saving. In this paper the bed rib structure was estimated with thermal characteristics. Using superposition principle, machine tool designer can describe every complicated heat generation in the machine tool thermal source. As thermal characteristics, thermal deformation of guide rail and column and Maximum-minimum temperature variation were selected. The size, configuration and direction against the thermal loading surface operated to the thermal characteristics. The DB chart was made following rib structure estimating thermal characteristics. With superposition principle and DB chart, machine tool designer can prognosticate the thermal characteristics without FEM analysis to every bed rib structure.

이중전압원 분리를 이용한 PMSM의 센서리스 제어 (A Sensorless PMSM Control Using the Separation of Two Voltage Source)

  • Jin-Woo Ahn;Sung-Jun Park;Dong-Hee Lee
    • 대한전기학회논문지:전기기기및에너지변환시스템부문B
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    • 제53권1호
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    • pp.1-7
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    • 2004
  • This paper presents a sensorless control strategy of a PMSM(Permanent Magnet Sycchoronous Motor). This method is very simple to compute the position angle of a rotor. A principle and a practical solution are described. A sensorless control algorithm is proposed to remove a mechanical position sensor. The theory is based on the superposition principle. The state equation of a motor is divided into two conditions: one is the state equation of exciting voltage and phase current in a constraint, the other is the state equation of back EMF(Electromotive Force) and phase current in a short circuit. Based on the analysis, short circuit current by back EMF is computed and then the information of position angle is calculated. The proposed method is verified by experimental results.

용접잔류응력장에서 피로균열의 전파에 따른 잔류응력 재분포에 대한 해석적 평가 (An Evaluation of Residual Stress Redistribution in the Welding Residual Stress Field Caused by Fatigue Crack Propagation by Finite Element Method)

  • 박응준;김응준
    • Journal of Welding and Joining
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    • 제26권6호
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    • pp.92-96
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    • 2008
  • An investigation was performed to predict residual stress redistribution for the crack propagation initially through tensile residual stress field. The analytical method, which is based on Dugdale model by finite element analysis using elastic analysis method considering the superposition principle, was proposed to estimate the redistribution of residual stress caused by crack propagation. The various aspect of distribution of residual stress caused by crack propagation was examined based on the configuration change of specimen. The analysis results show that the aspect of redistribution of residual stress caused by crack propagation depends on the width of the specimen provided that the initial distribution of residual stress is identical.

Numerical Analysis of the Contour Method for Measuring Residual Stresses in Laser Shock Peened Ti-6Al-4V Strips

  • Shin Shang-Hyon
    • Journal of Advanced Marine Engineering and Technology
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    • 제29권3호
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    • pp.290-296
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    • 2005
  • The contour method is based on the elastic superposition principle, and relies on deformations that occur when a residually stressed part is cut along a plane. During the cut, the part is constrained at a location along the cut so that deformations are restrained as much as possible. The displacement is applied to an elastic FE model of the half. When plasticity is involved in the relaxation process, the superposition principle is no longer valid, and stress error in the resulting measurement of residual stress would be caused. Residual stress states in a laser peened Ti-6Al-4V strip were taken for the FE simulation.