• Structural Engineering and Mechanics
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• 제35권3호
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• pp.349-364
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• 2010

The impact behaviour and the impact-induced damage in laminated composite cylindrical shell subjected to transverse impact by a foreign object are studied using three-dimensional non-linear transient dynamic finite element formulation. A layered version of 20 noded hexahedral element incorporating geometrical non-linearity is developed based on total Langragian approach. Non-linear system of equations resulting from non-linear strain displacement relation and non-linear contact loading are solved using Newton-Raphson incremental-iterative method. Some example problems of graphite/epoxy cylindrical shell panels are considered with variation of impactor and laminate parameters and influence of geometrical non-linear effect on the impact response and the resulting damage is investigated.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.239-245
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• 2015

In this paper, to examine the difference between the linear and non-linear static, dynamic analysis for a structure, a cantilevered beam was used. Then, an external transverse static and dynamic loads were applied at the free end of the beam. Classical theories were used for the linear analysis and the EDISON CSD solver, co-rotational dynamic FEM program, was used for nonlinear analysis. In the static analysis, effects of the load for the beam deflection were observed in the linear and nonlinear analysis. Then, normalized displacement of tip of the beam was predicted for different frequency ration and a significant difference was obtained in the vicinity of the resonant frequency. In addition, effects of frequency and time for the beam deflection were investigated to find the frequency delay.

• 한국터널지하공간학회 논문집
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• 제12권4호
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• pp.295-306
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• 2010

암석과는 달리 절리암반은 변형률 의존적 변형특성(탄성계수 및 감쇠비)을 나타낸다. 탄성파를 이용한 현장실험을 통해 미소변형률 수준에서 암반의 최대탄성계수를 얻을 수 있으며 이를 내진 설계에 반영하고 있으나, 미소 변형률 이상의 중변형률($10^{-4}{\sim}0.5%$) 영역의 동적거동에 대한 실험적인 규명과 이에 대한 수치적 적용은 전무한 실정이다. 본 연구에서는 변형률 의존적 전단탄성계수 및 감쇠비의 비선형 거동 특성을 반영하여 동적해석을 수행할 수 있는 FLAC3D 해석 모듈을 개발하였다. 리커 웨이브의 파동 변화를 분석하여 개발된 모듈에 대한 검증을 수행하였다. 절리 암반의 탄성파 전파특성과 동적 거동특성을 모사할 수 있는 절리암반 공진주 시험장비를 통하여 현장에서 채취한 절리암반의 변형률 의존적 전단탄성 계수의 감쇠 특성과 감쇠비의 증폭 특성을 획득하였다. 개발된 비선형 해석 모듈에 실험으로부터 획득된 거동 특성을 반영하여 수직구와 사갱의 접속부에 대한 내진 안정성 평가를 수행하였다. 내진해석 결과, 비선형 해석이 선형 해석보다 더 큰 연직변위와 수평변위 결과를 나타냈다. 라이닝의 휨압축응력은 수직구과 사갱의 접속부에서 집중되는 것으로 나타났으며 비선형해석의 경우 라이닝에 더 큰 휨압축응력이 발생되는 것으로 나타났다. 본 연구를 통하여 변형률 의존적 절리암반의 비선형 거동특성을 보다 깊이 있게 이해하고 해석 및 설계시 고려할 수 있을 것으로 사료된다.

• 대한조선학회논문집
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• 제29권4호
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• pp.152-172
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• 1992

대파고 파랑중을 항해하는 선박은 큰 선체 운동으로 인하여 수면하 단면 형상이 시시각각 크게 변하므로 자유 표면 조건, 물체 표면 조건의 비선형성에 의한 비선형 유체력의 영향이 무시될 수 없게 된다. 경우에 따라서는 선저가 파면으로부터 충격력을 받는 슬래밍 현상과 선수가 파도를 뒤집어 쓰는 청파 현상등과 같은 충격적 유체력이 선체에 가해지는 등 복잡한 문제가 발생하게 된다. 본 연구에서는 선체를 가변 단면보의 탄성체로 이상화하여 파랑중 선체 거동을 박육 단면보 이론에 의해 정식화하고 파랑 하중으로는 수면하 단면 형상 변화에 따른 비선형 유체력과 momentum slamming이론을 이용한 유체 충격력을 고려하여 대파고 파랑 중 탄성체인 선체의 응답을 추정하는 해석 기법을 개발하여 이를 기존의 실험결과와 비교 그 타당성을 확인하고, 이의 응용으로 본 기법에 의하여 4만톤급 정유 운반선에 적용하여 정면파 및 사파중에서 파고, 파장, 선속을 파라미터로 한 수치 계산을 수행하고 여러가지 파라미터 변화에 대한 선체 구조의 동적 강도 응답 특성을 계통적으로 분석하여 보았다. 본 연구에서 개발된 동적강도 해석법은 대파고 중에서 유체력의 비선형성 및 유체 충격력까지 고려한 해석기법이므로 신구조 방식 선박에 대한 직접 설계법의 확립 뿐만 아니라 슬래밍 등에 의한 선체 절손 사고의 원인 규명에도 유용하게 적용할 수 있을 것으로 사료된다.

• 소음진동
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• 제10권5호
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• pp.838-842
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• 2000

The vibration of an axially moving string is studied when the string has geometric non-linearity and translating acceleration. Based upon the von karman strain theory, the equations of motion are derived considering the longitudinal and transverse deflection. The equation for the longitudinal vibration is linear and uncoupled, while the equation for the transverse vibration is non-linear and coupled between the longitudinal and transverse deflections. These equations are discretized by using the Galerkin approximation after they are transformed into the variational equations, i.e. the weak forms so that the admissible and comparison functions can be used for the bases of the longitudinal and transverse deflections respectively. With the discretized nonlinear equations, the time responses are investigated by using the generalized-$\alpha$ method.

• 한국CDE학회논문집
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• 제7권1호
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• pp.1-8
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• 2002

A Hotchkiss spring has been widely utilized for commercial vehicle. Usually, the Hotchkiss spring has non-linear characteristics, i.e. it has a piecewise spring stiffness as well as hysterisis phenomenon. Therefore, the modeling of the Hotchkiss spring requires many considerations to fulfill satisfactory vehicle kinematic and dynamic relationships. Also, the spring has difficulties in modeling for presenting contact mechanism. In this paper, the modeling technique for the Hotchkiss spring has been descried. The modeling covers non-linear characteristics as well as contact problems for multi-body dynamic simulation. The force-displacement results are compared with experimental and FEM ones. Also, the comparison between three link type leaf spring model and proposed one has been considered in this paper.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 Asia Navigation Conference
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• pp.134-143
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• 2006

Out of all types of motions the critical motions leading to capsize is roll. The dynamic amplification in case of roll motion may be large for ships as roll natural frequency generally falls within the frequency range of wave energy spectrum typical used for estimation of motion spectrum. Roll motion is highly non-linear in nature. Den are various representations of non-linear damping and restoring available in literature. In this paper an uncoupled non-linear roll equations with three representation of damping and cubic restoring term is solved using a perturbation technique. Damping moment representations are linear plus quadratic velocity damping, angle dependant damping and linear plus cubic velocity dependant damping. Numerical value of linear damping coefficient is almost same for all types but non-linear damping is different. Linear and non-linear damping coefficients are obtained form free roll decay tests. External rolling moment is assumed as deterministic with sinusoidal form. Maximum roll amplitude of non-linear roll equation with various representations of damping is calculated using analytical procedure and compared with experimental results, which are obtained form forced tests in regular waves by varying frequency with three wave heights. Experiments indicate influence of non-linearity at resonance frequency. Both experiment and analytical results indicates increase in maximum roll amplitude with wave slope at resonance. Analytical results are compared with experiment results which indicate maximum roll amplitude analytically obtained with angle dependent and cubic velocity damping are equal and difference from experiments with these damping are less compared to non-linear equation with quadratic velocity damping.

• Steel and Composite Structures
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• 제32권4호
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• pp.509-519
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• 2019

In this paper, an analytical approach for the free vibration analysis of spiral stiffened functionally graded (SSFG) cylindrical shells is investigated. The SSFG shell is resting on linear and non-linear elastic foundation with damping force. The elastic foundation for the linear model is according to Winkler and Pasternak parameters and for the non-linear model, one cubic term is added. The material constitutive of the stiffeners is continuously changed through the thickness. Using the Galerkin method based on the von $K\acute{a}rm\acute{a}n$ equations and the smeared stiffeners technique, the non-linear vibration problem has been solved. The effects of different geometrical and material parameters on the free vibration response of SSFG cylindrical shells are adopted. The results show that the angles of stiffeners and elastic foundation parameters strongly effect on the natural frequencies of the SSFG cylindrical shell.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
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• pp.58-60
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• 2009

This paper deals with force characteristic analysis of linear switched reluctance motor using dynamic simulation. First, we calculated flux density of linear switched reluctance motor according to position. Second, analyzed normal force from flux density of linear switched reluctance motor according to position. Also, analysis result compares with data that is derived through a finite element analysis, and proved validity. However, linear switched reluctance motor has non linear characteristic, hence, analysis of propulsion force do not easy using analytical method. Therefore, we presented dynamic characteristic analysis model which is consisted at motor and sensor signal part, etc., and substitute circuit constant that get using magnetic equivalent circuit method, we confirmed propulsion force.

• 전기학회논문지
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• 제57권3호
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• pp.336-343
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• 2008

In this study, a transition of power quality was characterized by non-linear voltage electric equipments under voltage sag. The test was inputted voltage sag to IPC(Sag Generator) from AVR, and then to equipments by IPC which adjust voltage magnitude and duration. The load test which non-linear voltage electric equipments used PLC, Magnetic Contactor, SMPS, HID Lamp. The test result was different from each other according to a manufacturing companys, models, and equipments. PLC was greatly described to be stabilized voltage sag in case of no load then rated load. Magnetic Contactor was made a difference to phase angles on voltage sag, which was $0^{\circ}$, $30^{\circ}$, $60^{\circ}$, $90^{\circ}$. HPD Lamp was described to be stabilized the sodium lamp, and to be unstabilized the metal hailed lamp. The test result was showed CBEMA curve that stand for evaluated responsiveness of voltage sag. This study was tested description to dynamic characteristics on non-linear voltage electric equipment under voltage sag. There was hoped that power system designed the essential particulars.