• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.68-69
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• 2011

마그네슘 판재의 온간 스프링백 거동 예측을 위한 재료 거동 모델을 고찰하였다. V-굽힘 시험에 관한 기존 문헌의 결과와 비교하여 재료 모델의 타당성을 토하였다. 스프링백 거동의 정량화를 위해 온간 S-rail 프레스금형에 의한 성형 시험을 수행하였다. 성형 시험은 다양한 온도, 속도, 성형깊이 조건에서 수행하였으며 시험 결과를 서로 비교하였다. 재료 모델을 사용하여 S-레일 성형에 따른 스프링백 예측을 위한 유한요소해석을 수행하고 그 결과를 시험 측정값과 비교하였다. 이로부터 재료 모델의 한계와 가능성을 고찰하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.245-253
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• 2020

In this study, natural frequencies are compared using several pile-soil interaction (PSI) models to evaluate the effects of each model on resonance safety checks for a monopile type of wind turbine structure. Base spring, distributed spring, and three-dimensional brick-shell models represented the PSIs in the finite element model. To analyze the effects of the PSI models on a natural frequency, after a stiffness matrix calculation and Winkler-based beam model for base spring and distributed spring models were presented, respectively; natural frequencies from these models were investigated for monopiles with different geometries and soil properties. These results were compared with those from the brick-shell model. The results show that differences in the first natural frequency of the monopiles from each model are small when the small diameter of monopile penetrates hard soil and rock, while the distributed spring model can over-estimate the natural frequency for large monopiles installed in weak soil. Thus, an appropriate PSI model for natural frequency analyses should be adopted by considering soil conditions and structure scale.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.2
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• pp.61-69
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• 2011

In this paper, the factors affecting the dynamic characteristics of a polyurethane spring restoring disk bearing are analysed to predict the dynamic behavior of the bearing. The prediction results and the test results are compared. The Young's modulus of the polyurethane spring, which varies according to strain of spring and the friction coefficient, of PTFE (PolyTetraFluoroEthylene), which varies according to the velocity and pressure of PTFE, are considered as the factors influencing the dynamic characteristics. W-PTFE virgin products are used and polyurethane springs are produced for the tests. The equation related to changing the friction coefficient and the modulus of elasticity are obtained through an inverse estimation of the test results. The estimation results, considering the factors affecting the dynamic characteristics, simulate the test results more appropriately than the estimation without the consideration of those factors.

• Proceedings of the KIEE Conference
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• summer
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• pp.1016-1018
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• 2004

최근 배전용 차단기의 조작방식은 스프링 구동 방식에서 영구자석 엑츄에이터(PMA) 구동방식으로 바뀌고 있다. PMA로 작동하는 중고압 차단기는 여자전류 권선의 수에 의해 단권선형과 이권선형으로 구분한다. 본 논문에서는 PMA의 동특성을 해석하기 위하여 유한요소법과 외부회로 방정식을 결합하였다. 가동부의 움직임을 고려하여 자계분포를 해석하였으며 가동부의 속도와 흡인력을 구하여 비교하였다. 해석된 결과는 PMA 설계에 이용될 수 있을 것으로 기대한다.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.125-133
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• 1993

Most studies on the vibration analysis of a beam-column with ends elastically restrained and various intermediate constraints have been based on the Euler beam theory, which is inadequate for beam-columns of low slenderness ratios. In this paper, analytical methods for vibration and dynamic sensitivity of a Timoshenko beam-column with ends elastically restrained and various intermediate constraints are presented. Firstly, an exact solution method is shown. Since the exact method requires considerable computational effort, a Rayleigh-Ritz analysis is also investigated. In the latter two kinds of trial functions are examined for comparisions : eigenfunctions of the base system(the system without intermediate constraints) and polynomials having properties corresponding to the eigenfunctions of the base system. The results of some numerical Investigations show that the Rayleigh-Ritz analysis using the characteristic polynomials is competitive with the exact solutions in accuracy, and that it is much more efficient in computations than using the eigenfunctions of the base system, especially in the dynamic sensitivity analysis. In addition, the prediction of the changes of natural frequencies due to the changes of design variables based on the first order sensitivity is in good agreements with that by the ordinary reanalysis as long as the changes of design variables are moderate.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.328.2-328
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 2003.10a
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• pp.311.2-311.2
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• 2003

• Computational Structural Engineering
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• v.7 no.2
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• pp.77-87
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• 1994

Vibrational analysis of slab tracks for HSR(High Speed Rail) is performed in order to find dynamic characteristics and to control noise and vibration for the tracks. Wheel-rail interactive force is included in the analysis by modelling the vehicle and track as an unsprung mass and elastically-supported-double-beam respectively, and both are assumed to be connected by the Hertzian spring. From this study, it has been found that vibration in the track and the force transmitted to the infrastructure could be reduced by controlling elasticity, mass and stiffness of the track supporting system appropriately.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.147-153
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• 2004

This paper presents an analytical modeling technique fer representing a hysteretic behavior of a multi-leaf spring used for a large truck. It divides a nonlinear hysteretic curve of the multi-leaf spring into four parts; loading part, unloading part and two transition parts. It provides conditions fur branching to a part of the curve corresponding to a current multi-leaf spring status. This paper also presents a computational modeling technique of the multi-leaf spring. It models the multi-leaf spring with three links and a shackle. It assumes those components as rigid bodies. The links are connected by rotational joints, and have rotational springs at the joints. The spring constants of the rotational springs are computed with a force from the analytical model of the hysteretic curve of the multi-leaf spring. Static and dynamic tests are performed to verify the reliability of the presented techniques. The tests are performed with various amplitudes and excitation frequencies. The hysteretic curves from the tests are compared with those from the simulations. Since th e presented techniques reproduce the hysteretic characteristic of the multi -leaf spring faithfully, they contribute on improving the reliability of the computational model of a large truck.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.13-22
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• 1990

A general analysis method is proposed for analysis of the superposed structures with geometric and material nonlinearities. It is presumed that no friction occurs between structures. It utilizes a shell element for the geometric and material nonlinearities and imposes various deformation constraints for the contact and interaction between structures. To show the reliability and effectiveness of this method, superposed cantilevers for which exact solutions can be obtained and holddown spring assemblies which are now used in PWR reactors are chosen as analysis models. The results of analyses were compared with exact solution in the case of cantilevers and with test results in the case of holddown spring assemblies. The analysis results obtained by this method showed good agreement with the reference values.