• 대한기계학회논문집A
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• 제32권11호
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• pp.1022-1027
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• 2008

TPE is used as alternative for rubber, the best example is the weather strip for automobile. The nonlinear material properties of weather strip were important to predict the behaviors of weather strip. Uniaxial tension and equi-biaxial tension tests were performed to achieve the nonlinear material constant and stress-strain curves. The nonlinear material constant of weather strip is evaluated by using the nonlinear finite element analysis. In this paper, the prediction for weather strip is analyzed by using commercial finite element program, ANSYS. The nonlinear finite element analysis of weather strip is executed to predict the behavior of weather strip for automobile.

• 한국광학회:학술대회논문집
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• 한국광학회 2002년도 하계학술발표회
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• pp.94-95
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• 2002

Photonic crystal (PC) has special interests for their promising applications in three-dimensional photon control and integrated devices. In a nonlinear photonic crystal (NPC), optical intensity in a defect layer is greatly increased due to the location function of NPC and nonlinearity. The nonliearity of the defect layer is very much enhanced because the group velocity is reduced and the interaction time between light and nonlinear medium in the defect layer is enlarged. (omitted)

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.312-317
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• 1997

This paper present an optimum design for the rotor-bearing system of a high-speed (80000RPM) ultra-centrifuge supported by ball bearings with nonlinear stiffness characteristics. To obtain the nonlinear bearing stiffnesses, a ball bearing is modelled in five degrees of freedom and is analyzed quasi-statically. The dynamic behaviors of the nonlinear rotor-bearing system are analyed by using a transfer-matrix method iteratively. For optimum design, minimizing the weight of a rotor is used as a cost function and the Augmented Lagrange Multiplier (ALM) method is employed. The result shows that the rotor-bearing system is optimized to obtain 8% weight reduction.

• 콘크리트학회논문집
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• 제23권5호
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• pp.569-579
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• 2011

주기하중을 받는 철근콘크리트 벽체는 형상비, 배근상세, 재하 조건 등에 따라 복잡한 비탄성 거동을 보인다. 이 연구에서는 벽체의 휨-압축 거동과 전단거동을 간편하게 고려할 수 있는 거시 요소를 이용한 비선형 해석 방법을 개발하였다. 철근콘크리트 벽체의 휨-압축 거동 및 전단거동은 각각 길이 방향 및 대각 방향 1축 요소로 이상화된다. 1축 요소는 콘크리트와 철근으로 구성되고, 비선형 재료 모델로서 1축 상태에서 반복하중을 받는 콘크리트와 철근의 주기거동 모델을 사용한다. 검증을 위하여 제안된 방법을 사용하여 주기하중을 받는 철근콘크리트 단일벽 및 병렬벽의 비선형 해석을 수행하였다. 그 결과 제안된 방법은 휨-압축 거동이 지배적인 세장한 벽체와 전단거동이 지배적인 낮은 벽체의 주기거동을 정확하게 예측하였다. 제안된 거시 해석 모델은 모델링이 편리하고 수치해석의 안정성이 우수하므로, 전단벽 및 코어벽이 사용된 건물의 비선형 해석을 위한 범용 프로그램으로 개발이 용이할 것으로 판단된다.

• Advanced Composite Materials
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• 제18권3호
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• pp.265-285
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• 2009

Off-axis compressive deformation behavior of a unidirectional CFRP laminate at high temperature and its strain-rate dependence in a quasi-static range are examined for various fiber orientations. By comparing the off-axis compressive and tensile behaviors at an equal strain rate, the effect of different loading modes on the flow stress level, rate-dependence and nonlinearity of the off-axis inelastic deformation is elucidated. The experimental results indicate that the compressive flow stress levels for relatively larger off-axis angles of $30^{\circ}$, $45^{\circ}$ and $90^{\circ}$ are about 50 percent larger than in tension for the same fiber orientations, respectively. The nonlinear deformations under off-axis tensile and compressive loading conditions exhibit significant strain-rate dependence. Similar features are observed in the fiber-orientation dependence of the off-axis flow stress levels under tension and compression and in the off-axis flow stress differential in tension and compression, regardless of the strain rate. A phenomenological theory of viscoplasticity is then developed which can describe the tension-compression asymmetry as well as the rate dependence, nonlinearity and fiber orientation dependence of the off-axis tensile and compressive behaviors of unidirectional composites in a unified manner. It is demonstrated by comparing with experimental results that the proposed viscoplastic constitutive model can be applied with reasonable accuracy to predict the different, nonlinear and rate-dependent behaviors of the unidirectional composite under off-axis tensile and compressive loading conditions.

• 한국강구조학회 논문집
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• 제10권1호통권34호
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• pp.73-83
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• 1998

초기인장력 변화에 따른 구조물의 동적거동은 초기인장력의 감소에 따라 기하학적 비선형성은 증가하고 고차모드의 영향이 지배적이고 phase portrait는 period attractor가 복잡한 양상으로 발생하였으며, 초기인장력의 증가에 따라 비선형 해석결과와 선형 해석결과의 차이는 감소하였고 1차모드가 지배적인 모드로 작용하고 phase portrait는 period attractor가 일정한 영역에서 규칙적으로 발생함을 알 수 있었다. 이와 같은 결과는 Lanczos 모드해석과 같이 모드축소법을 이용하는 비선형 동적해석에서 유용한 정보를 제공할 수 있으며. 현실적으로 비선형 동적해석에 소요되는 시간과 노력이 매우 크다는 것을 감안할 때 초기인장력에 따라 모드축소법에 기여하는 모드를 결정하면 정확한 동적응답을 얻을 수 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.467-471
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• 2009

In this study a cantilevered carbon nanotube(CNT) switch was investigated with the linear and the nonlinear structural models incorporating the electrostatic force and van der Waals interactions between the CNT and ground surface. Due to the applied voltage and van der Waals interactions the CNT deforms statically and dynamically and finally pull into the surface. When the nonlinear model is considered in case of the relatively large gap between the CNT and the surface, the static pull-in voltage was increased due to the nonlinear hardening effect. Also the dynamic response was investigated with the different external dc and ac voltages. The CNT shows various dynamic behaviors and instabilities including dynamic pull-in. Based on this study, further research on the dynamic and nonlinear stability of CNT nanodevices should be requested to develop the new type of nano switches or nano-memory.

• 대한기계학회논문집
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• 제17권10호
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• pp.2634-2645
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• 1993

Dome structures of pressure vessels subjected to internal pressure are usually analyzed by linear elastic theory assuming small deformation. Geometric and material nonlinear behaviors appear in actual dome structures because of large deformation and loads exceeding yield strength. In this paper, linear and nonlinear analyses were performed for various hemispherical and torispherical domes to check the effects of geometric and material nonliearity on the stress and displacement by the finite element method. The effect of the geometric nonlinearity decreased the stress levels a lot for very thin general torispherical domes, which enables more realistic and effective design. The material nonlinear effects are negligible for hemispherical and optimum torispherical domes, and those are large for most of the general torispherical domes.

• Smart Structures and Systems
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• 제26권5호
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• pp.631-640
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• 2020

In this paper, nonlinear vibration behaviors of multi-phase Magneto-Electro-Elastic (MEE) doubly-curved nanoshells have been studied employing Jacobi elliptic function method. The doubly-curved nanoshell has been modeled by using nonlocal elasticity and classic shell theory. An exact estimation of nonlinear vibrational behavior of smart doubly-curved nanoshell has been obtained via Jacobi elliptic function method. This method can incorporate the influences of higher order harmonics leading to an exact estimation of nonlinear vibration frequency. It will be indicated that nonlinear vibrational frequency of doubly-curved nanoshell relies on nonlocal effect, material composition, curvature radius, center deflection and electro-magnetic field.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.703-708
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• 2006

The cantilever beam with nonlinearity has many dynamic characteristics of nonlinear vibration. Nonlinear terms of a flexible cantilever beam include inertia, spring, damping, and warping. When the beam is given basic harmonic excitation, it shows planar and nonplanar vibrations due to one-to-one resonance. And when the one-to-one resonance occurs, the flexible beam shows different behaviors in those vibrations. For the one-to-one resonance occurring in each mode, the phase value of the planar vibration is different from that of the nonlinear vibration. This paper investigates the phase change and the phase difference between such planar and nonplanar vibrations which are caused by one-to-one resonance.