• 한국강구조학회 논문집
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• 제10권4호통권37호
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• pp.691-700
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• 1998

본 연구에서는 역대칭 또는 비대칭 적층쉘에 대한 Von Karman-Donnell 운동방정식을 기초로 한 다중 모드 접근법을 이용하여 양단이 단순지지 되고 다른 임의지지가 단순 또는 고정지지인 원통 쉘의 비선형 거동에 대해 연구하였다. 방정식은 모든 경계조건에 대해 만족하며, 변위함수는 최저 진동모드와 원주 방향의 변위의 연속성 조건을 만족하는 것으로 한다 비선형 진동 방정식은 Galerkin 법을 이용하여 유도하였고, 비선형 진동수는 조화평균법을 이용하여 적층 매개변수, 재료 상수, 종횡비 및 진동 진폭의 함수로서 표시하였다. 초기 진폭의 영향에 대해서는 4가지 형태의 경계조건에 대한 비선형 진동 결과를 비교 검토하였다.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.325-339
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• 2020

This study presents a practical application of topology optimization (TO) technique to seek the best form of perforated steel plate shear walls (PSPSW) in simple frames. For the numerical investigation, a finite element model is proposed based on the recent particular form of PSPSW that is called the ring-shaped steel plate shear wall. The TO is applied based on the sensitivity analysis to maximize the reaction forces as the objective function considering the fracture tendency. For this purpose, TO is conducted under a monotonic and cyclic loading considering the nonlinear behavior (material and geometry) and buckling. Also, the effect of plate thickness is studied on the TO results. The final material volume of the optimized plate is limited to the material volume of the ring-shaped plate. Finally, an optimized plate is introduced and its nonlinear behavior is investigated under a cyclic and monotonic loading. For a more comprehensive view, the results are compared to the ring-shaped and four usual forms of SPSWs. The material volume of the plate for all the models is the same. The results indicate the strength, load-carrying, and energy dissipation in the optimized plate are increased while the fracture tendency is reduced without changing the material volume.

• 전기학회논문지P
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• 제51권3호
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• pp.142-148
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• 2002

Considerable progress has been made in organic photorefractive materials, since the first observation of photorefractive phenomena from organic materials. Within recent years, a large number of organic photorefractive materials, especially amorphous materials, have been developed based on polymeric composites, fully functional polymers and the multi-functional chromophore approach. Among these organic photorefractive materials, some of them containing carbazole components as a charge transporting function have been demonstrated to exhibit high performance photorefractive effects. The carbazole building blocks with charge transporting function or multifunctions play a very important role in photorefraction. In this paper, it confirmed that acceptor-substituted carbazoles show the multifunctionality both of photoconductivity and electro-optic(EO) activity and photorefractive materials newly can be developed with acceptor-substituted carbazoles.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.162-166
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• 1996

This paper presents a position control of ultra-precision machine tool post using piezoelectric material. A stack-type piezoelectric actuator Is employed in a hinge-type tool holder. An assumed linear transfer function of the practical nonlinear plant is established through the comparison of transfer functions and step responses in the experiments and the simulations. Several types of feedforward/feedback controllers are designed via computer simulations using the assumed linear transfer function. The position tracking control experiments are undertaken to show the control efficiency of each controller.

• 한국정밀공학회지
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• 제18권2호
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• pp.186-191
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• 2001

A crack with electrically impermeable surfaces in an electrostrictive material subjected to uniform electric loading is analysed. The effect of electric yielding on stress intensity factor is investigated by using a small scale yielding model and a strip yield zone model. Complete forms of electric fields and elastic fields are derived by using complex function theory. The electrical yield zone shapes for two models are different each other. The two models, however, predict similar yield zone sizes under the small scale yielding conditions. It is found that the influence of electric yielding on the stress intensity factor is insensitive to the modeling of the electrical yield zone shape.

• Journal of applied mathematics & informatics
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• 제23권1_2호
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• pp.461-470
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• 2007

Parameter identification is studied in viscoelastic rods by solving an inverse problem numerically. The material properties of the rod, which appear in the constitutive relations, are recovered by optimizing an objective function constructed from reference strain data. The resulting inverse algorithm consists of an optimization algorithm coupled with a corresponding direct algorithm that computes the strain fields given a set of material properties. Numerical results are presented for two model inverse problems; (i)the effect of noise in the reference strain fields (ii) the effect of minimal reference data in space and/or time data.

• 한국군사과학기술학회지
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• 제5권2호
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• pp.207-216
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• 2002

In this paper, the study on the behavior of the deformation of brittle material, such as concrete, ceramic, was peformed by comparison of Lagrangian technique and Smoothed Particle Hydrodynamics using commercial nonlinear hydrodynamic numerical program, Autodyn_2D. The effect of SPH technique was proved by investigating the behavior of material deformation, velocity profile and pressure profile.

• 한국강구조학회 논문집
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• 제18권6호
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• pp.707-716
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• 2006

본 논문에서는 고등해석과 유전자 알고리즘을 이용한 반강접 강뼈대 구조물의 직접설계시스템의 최적화를 수행하였다. 고등해석은 접합부의 비선형, 기하학적 비선형 및 재료적 비선형을 고려한다. 기하학적 비선형은 안정함수를 사용하여 고려하였으며, 재료적 비선형은 CRC 접선 탄성계수와 포물선 함수를 사용함으로서 고려하였다. 접합부의 비선형은 Kishi와 Chen이 제안한 3가지 매개변수를 가지는 파워모델을 사용하여 고려하였다. 최적화 기법으로는 유전자 알고리즘을 사용하였다. 목적함수는 구조물의 중량을 사용하였으며, 제약조건식은 구조시스템의 하중-저항능력, 처짐, 층간 수평변위 및 연성요구 조건을 고려하였다. 제안된 방법에 의한 설계결과를 기존의 방법들과 비교하였다.

• 대한기계학회논문집A
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• 제31권12호
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• pp.1165-1172
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring, nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are transformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response field of linear analysis as that of nonlinear analysis. Shape optimization of the spring is carried out based on EL. The objective function is defined by minimizing the maximum stress in the spring while mass is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear response analysis. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• Composites Research
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• 제12권4호
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• pp.1-7
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• 1999

비선형 하중/변위 거동을 나타내는 모재 지배 복합재료의 피로수명 예측을 이론과 실험에 의해 연구하였다. 재료의 비선형성을 고려하기 위해 초기 피로계수와 탄성계수의 관계를 나타내는 응력함수를 도입하였다. 피로계수와 참고계수 개념을 기반으로 하여 새로운 피로수명 예측식이 가한 하중 수위의 함수로 유도되었다. 예측 결과는 직교이방성 탄소섬유/에폭시 적층판을 사용한 원통형 시편의 비틀림 피로 실험과 비교되었으며, 제안된 식은 실험치와 잘 일치하였다.