• 제목/요약/키워드: Cross-anisotropy

검색결과 74건 처리시간 0.025초

직교 이방적 사질토의 미시역학적 탄소성 모델링: I. 정식화 (Elastic-plastic Micromechanics Modeling of Cross-anisotropic Granular Soils: I. Formulation)

  • 정영훈;정충기
    • 한국지반공학회논문집
    • /
    • 제23권3호
    • /
    • pp.77-88
    • /
    • 2007
  • 본 연구에서는 사질토의 탄성 및 탄소성 거동을 모사하기 위한 미시역학 기반의 구성 모델을 개발하였다. 개발 모델은 접촉 방향의 공간 분포를 통계적으로 처리한 조직 이방성, 응력비에 따른 조직 이방성의 변화, 간극비 변화에 따른 접촉점 수의 변화, 그리고 미시적 탄성-탄소성 접촉 강성을 고려하였다. 금속 재료에 대한 시험결과를 이용하여 미시적 탄소성 접촉 강성 모델을 수직 접촉력과 입자의 항복 접촉력에 대한 거듭제곱 함수의 형태로 유도하였다. 모델 변수를 정량적으로 평가하기 위해 직교 이방 탄성 계수의 근사식을 유도하였다.

복합재료 H-형 단면 보의 동적응답 해석 (Dynamic Response Analysis of Composite H-type Cross-section Beams)

  • 김성균;송오섭
    • 한국소음진동공학회논문집
    • /
    • 제20권6호
    • /
    • pp.583-592
    • /
    • 2010
  • Equations of motion of thin-walled composite H-type cross-section beams exposed to concentrated harmonic and non-harmonic time-dependent external excitations, incorporating a number of nonclassical effects of transverse shear, primary and secondary warping, and anisotropy of constituent materials are derived. The forced vibration response characteristics of a composite H-type cross-section beam exhibiting the circumferentially asymmetric stiffness(CAS) configuration are exploited in connection with the structural bending-torsion coupling resulting from directional properties of fiber reinforced composite materials.

Cholesteric 액정질서를 지닌 Hydroxypropyl Chitosan 가교필름의 제조와 팽윤거동 (Preparation and Swelling Behavior of Cross-Linked Films of Hydroxypropyl Chitosan Possessing Cholesteric Liquid-Crystalline Order)

  • 마영대;김경희
    • 폴리머
    • /
    • 제24권3호
    • /
    • pp.418-430
    • /
    • 2000
  • 알칼리키토산과 프로필렌옥사이드를 반응시킴에 의해 유방성 및 열방성 액정상을 형성하는 새로운 히드록시프로필키토산(HPCTO)을 합성함과 동시에 HPCTO/메탄올의 유방성 액정용액에 glyoxal첨가하여 주형시킴에 의해 HPCTO의 가교필름들을 제조하였다. 가교필름들의 열 및 팽윤 특성을 검토하였다. 필름들은 cholesteric 액정상의 특징적인 지문조직을 나타내었으며 이들의 pitch는 온도 및 가교제의 농도가 증가할수록 증가하였다. 가교시료들은 물과 메탄을 중에서 이방성 팽윤을 나타내었으며, 이러한 사실은 HPCTO분자들간에 2차원적인 가교가 우선적으로 일어남을 시사한다. 이방성 팽윤의 정도는 용매의 종류에 크게 의존하나 검토된 가교제의 농도에는 의존하지 않았다.

  • PDF

변형형상에 따른 정규압밀 점성토의 압밀계수 변화 (The Influence of Deformation Modes on the Coefficient of Consolidation in the Normally Consolidated Clay)

  • 박재현;정영훈;정충기
    • 한국지반공학회:학술대회논문집
    • /
    • 한국지반공학회 2004년도 춘계학술발표회
    • /
    • pp.823-830
    • /
    • 2004
  • Consolidation tests under various deformation modes were performed to investigate the effect of deformation modes on the coefficient of consolidation in the normally consolidated clay in remolded and undisturbed clay. The degree of soil anisotropy was evaluated using cross-anisotropic elasticity theory suggested by Graham et al.(1983). Experimental results showed that the vertical compressibility was larger than the horizontal compressibility by $12{\sim}21%$ for the remolded clay and by $23{\sim}60%$ for the undisturbed clay, respectively. The results of a series of consolidation tests under the specific deformation modes showed that the coefficient of consolidation under 1 dimensional vertical strain condition was larger than that under 3 dimensional strain condition due to different deformation mode. Furthermore, the coefficient of consolidation under 1 dimensional vertical strain condition was larger than that under 1 dimensional horizontal strain condition by $40{\sim}60%$ in undisturbed clay, which clearly emphasized the significant effect of soil anisotropy on the rate of consolidation. Consequently, it can be concluded that the anisotropic deformation modes of soils, especially naturally deposited clays, should be taken into account for more accurate evaluation of the coefficient of consolidation.

  • PDF

복합재료 H형 단면 보의 자유진동 해석 (Free Vibration Analysis of Composite H-Type Cross-section Beams)

  • 김성균;송오섭
    • 한국소음진동공학회논문집
    • /
    • 제20권5호
    • /
    • pp.492-501
    • /
    • 2010
  • Equations of motion of thin-walled composite H-type cross-section beams incorporating a number of nonclassical effects of transverse shear and primary and secondary warping, and anisotropy of constituent materials are derived. The vibrational characteristics of a composite thin-walled beam exhibiting the circumferentially asymmetric stiffness system(CAS) and the circumferentially uniform stiffness system(CUS) are exploited in connection with the bending-transverse shear coupling and the bending-twist coupling resulting from directional properties of fiber reinforced composite materials.

랜덤하중이 가해진 복합재료 H-형 보의 동적 응답 해석 (Dynamic Response Analysis of Composite H-Type Cross-Section Beams to Random Loads)

  • 김성균;송봉건;송오섭
    • 한국소음진동공학회:학술대회논문집
    • /
    • 한국소음진동공학회 2011년도 추계학술대회 논문집
    • /
    • pp.130-135
    • /
    • 2011
  • A study of the bending-extension-transverse shear coupled random response of the composite beams with thin-walled open sections subjected to various types of concentrated and distributed random excitations is dealt with in this paper. First of all, equations of motion of thin-walled composite H-type cross-section beams incorporating a number of nonclassical effects of transverse shear and primary and secondary warping, and anisotropy of constituent materials are derived. On the basis of derived equations of motion, analytical expressions for the displacement response of the composite beams are derived by using normal mode method combined with frequency response function method.

  • PDF

임의의 표본상호상관함수와 비정규확률분포를 갖는 다중 난류시계열의 디지털 합성방법을 이용한 풍속데이터 시뮬레이션 (Wind Data Simulation Using Digital Generation of Non-Gaussian Turbulence Multiple Time Series with Specified Sample Cross Correlations)

  • 성승학;김욱;김경천;부정숙
    • 한국대기환경학회지
    • /
    • 제19권5호
    • /
    • pp.569-581
    • /
    • 2003
  • A method of synthetic time series generation was developed and applied to the simulation of homogeneous turbulence in a periodic 3 - D box and the hourly wind data simulation. The method can simulate almost exact sample auto and cross correlations of multiple time series and control non-Gaussian distribution. Using the turbulence simulation, influence of correlations, non-Gaussian distribution, and one-direction anisotropy on homogeneous structure were studied by investigating the spatial distribution of turbulence kinetic energy and enstrophy. An hourly wind data of Typhoon Robin was used to illustrate a capability of the method to simulate sample cross correlations of multiple time series. The simulated typhoon data shows a similar shape of fluctuations and almost exactly the same sample auto and cross correlations of the Robin.

RIE 식각시 발생하는 비등방도 변화에 따른 머리빗형 액튜에이터의 동작 특성 분석 (Operation Characteristic Analysis of a Comb Actuator due to a Anisotropy Variation in RIE Etching)

  • 김봉수;박호준;박정호
    • 센서학회지
    • /
    • 제8권5호
    • /
    • pp.368-376
    • /
    • 1999
  • 본 논문에서는 머리빗형 액튜에이터의 제작 공정 중에서 RIE 식각 공정시 발생하는 식각의 비등방도의 변화에 의해서 머리빗형 액튜에이터의 스프링 상수, 공진 주파수, 정전 구동력 과리고 진동자 변위 등에서 발생하는 동작 특성이 설계 값으로부터 변화되는 것을 예측하였다. 이를 위해 $6\;{\mu}m$ 두께의 폴리실리콘에 대한 RIE 식각 실험을 수행하여 RF power, $Cl_2$ 유량 그리고 챔버내 압력에 따른 비등방도를 측정하였다. 실험 결과에서 RF Power, $Cl_2$ 유량, 그리고 챔버내 압력이 증가할수록 비등방도 감소하였다. 이러한 비등방도 감소에 따른 머리빗형 구조물의 동작 특성을 세 가지 다른 지지빔의 경우에 대해 예측하였는데 세 가지는 fixed-fixed, crab-leg, 그리고 double crab-leg 구조이다. 비등방도가 감소함에 따라 즉, 지지빔의 단면이 직사각형이 아니고 사다리꼴이 되면서, 머리빗형 액튜에이더의 스프링 상수, 공진 주파수, 그리고 정전 구동력은 감소하였지만 질량체의 변위는 증가하였다. 그리고 세 가지 구조물 중에서 double crab-leg 지지빔을 갖는 머리빗형 액튜에이터의 특성이 비등방도에 의해 가장 큰 영향을 받는 것으로 나타났다.

  • PDF

원통 CFRP 구조재의 굽힘 특성 평가 (Evaluation of Bending Characteristics for Carbon FRP Structure having Circle Cross-section)

  • 김정호;김지훈
    • 한국생산제조학회지
    • /
    • 제20권2호
    • /
    • pp.202-206
    • /
    • 2011
  • Works on the strength and stiffness in the structural members are carried out widely with various material and cross-sections with ever increasing safety concerns, they are presently applied in various fields including railroad trains, air crafts and automobiles. In addition to this, problem of lighting structural members became important subject by control of exhaust gas emission, fuel economy and energy efficiency. So, Light weight of member structures is necessary for the high performance and various functions. In this study, the CFRP flat and circular member was manufactured by CFRP prepreg sheet in autoclave. Carbon FRP is an anisotropy material whose mechanical properties change with its fiber orientation angle, so this study apply to the effects of the fiber orientation angle on the bending characteristics of the member. Each CFRP flat and circle are compared by strength and stiffness.

Identification of linearly unstable modes in the near-Earth current disruption

  • Mok, Chin-Ook;Ryu, Chang-Mo
    • 한국우주과학회:학술대회논문집(한국우주과학회보)
    • /
    • 한국우주과학회 2009년도 한국우주과학회보 제18권2호
    • /
    • pp.44.1-44.1
    • /
    • 2009
  • Identification of wave characteristics during current disruption events in the near-Earth geomagnetic tail region (~ 10 RE) is important to understand the substorm onset mechanism. In this paper, linear stability analysis in the ion-cyclotron grequency range, considering temperature anisotropy and cross-field flow is presented. It is found that the ion-cyclotron drift waves propagating in a quasi-perpendicular direction with respect to the ambient magnetic field are characterized by low frequencies ($\omega$ < $0.5{\Omega}ci$), while quasi-parallel waves have frequencies close to the ion-cyclotron frequency ($\omega{\sim}{\Omega}ci$). This finding is consistent with the observation by THEMIS spacecraft of a current disruption event in which a similar high- and low-frequency band structure is also present [A. T. Y. Lui, et al., J. Geophys. Res. 113, A00C06 (2008)]. It is also found that the quasi-perpendicular mode is excited by the ion cross-field flow.

  • PDF