• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.211-216
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• 2012

This paper presents methods to reduce the deflection of the battery-supporting structure on on-line electric vehicles (OLEVs). First, by testing various battery locations, a location is found that increases the dynamic stiffness of the OLEV. Second, static analysis is conducted to analyze the maximum deflection caused by the battery weight. In order to reduce the amount of deflection, the contributions of the battery-supporting structures are analyzed, and reinforcements are inserted. Then, another static analysis is conducted to compare the results of the base model and modified model. Consequently, through the static analysis, both the base model and modified model are similarly improved in terms of deflection, but the modified model is better than the base model at reducing the mass.

• Korean Journal of Ecology and Environment
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• v.47 no.spc
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• pp.74-82
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• 2014

A perennial plant species of Ranunculaceae, Pulsatilla tongkangensis is a very rare species only found in limestone vegetation of South Korea. It is not only rare but also has great value as a horticultural resource, thus resulting in serious problems of overexploitation and habitat disturbance. For the conservation of the rare species and its development as a resource, the study was conducted with the following three aims: first, to investigate any new geographical distribution of the species; second, to identify the site condition and vegetation structure of its habitat; and third, to compare the ecology of P. tongkangensis in other microhabitats such as rock, slope and ridge area. A new distribution was found in limestone vegetation at Danyang-gun, Chungcheongbuk-do. It was, therefore, confirmed that the distribution of P. tongkangensis exactly coincides with the area of distribution of limestone, indicating a possibility that the species might be a calcicole. 87% of the microhabitats found in rocks. Compared to P. tongkangensis, at ridges or slopes, number of P. tongkangensis plants were few in rocks. It is possibly due to the lack of microhabitats that could settle in rocky areas. Once established on rocks, however, plants grew large enough to flower with higher number of leaves and flowers per plant, resulting in higher flowering rate on rocky areas. Cracks in/between rocks are likely to be safe places for the plants with favorable light conditions, abundant fine particles to root down and reduced competition for resources. Yet, further research is necessary in terms of determining whether the species is indeed a calcicole, whether other limiting factors work in its establishment stage, and genetic diversity exists in the population.

• Computational Structural Engineering
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• v.6 no.2
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• pp.95-102
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• 1993

A modeling method is described to provide a smaller structural dynamic model which can be used to compare finite element model of a structure with its experimental counterpart. A structural dynamic model is assumed to be represented by dynamic stiffness matrix. To validate a finite element model, it is often necessary to condense a large degrees of freedom (dofs) to a relatively small number of dofs. For these purpose, static reduction techniques are widely used. However, errors in these techniques are caused by neglecting frequency dependent terms in the functions relating slave dofs and master dofs. An alternative method is proposed in this paper in which the frequency dependent terms are considered by expressing the reduced dynamic stiffness matrix with orthogonal polynomials. The reduced model has finally a minimum set of dofs, such as sensors and excitation points and it is under the same condition as the physical system. It is proposed that the reduced model can be derived from finite element model. The procedure is applied to example structure and the results are discussed.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.4 s.19
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• pp.107-113
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• 2004

In order to model a connection part between a control fin and actuator, the related characteristics of a dynamic stiffness were extracted from experiments. These characteristics include the static stiffness of a control fin and the dynamic stiffness of an actuator, so they are called the mixed dynamic stiffness here. This mixed dynamic stiffness is used as the boundary condition of a control fin connected to an actuator when the flutter characteristics are analyzed. The simulated stiffness of an actuator is corrected from the experiment results and the mixed dynamic is finally formulated in the domain of frequencies.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.129-137
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• 2002

Elastomers, which are used engine mounts and body mount rubbers, are traditionally designed for NVH use in vehicles, and for vibration isolation in specific frequency range. According to the measurement of the characteristics of the SUV's engine mounts, there are variability in same engine mount properties. Static and dynamic stiffness of the SUV's engine mounts are changed due to the driving miles accumulated. The pre-load of body mount rubbers are changed due to the empty vehicle weight, passenger's weight and gross vehicle weight. And the dynamic stiffness of body mount rubbers are changed very hard above 150Hz frequency range.

• Journal of Power System Engineering
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• v.1 no.1
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• pp.91-97
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• 1997

Recently, it is increased by degrees to construct complex and large structures. In general, in order to solve the dynamic problem of these structures they have used finite element method(FEM). In this method, however, it is necessary to prove whether its results are correct or not. Therefore it requires much effort, time and many expenses for dynamic analysis of complex and large structures. Authors have developed the transfer dynamic stiffness coefficient method(TDSCM) which is the new vibration analysis method for complex and large structures on personal computer, and confirmed that the results of this method are good for these structures on personal computer. In this paper, TDSCM is applied to the torsional vibration analysis for the shaft system which consist of concentrated disks and shafts of continuous body. First, we formulate algorithms for torsional free and forced vibration analysis, and compare the results of TDSCM and FEM.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.1
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• pp.83-94
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• 1999

본 연구에서는 시스템의 해석적 모델과 측정된 응답을 이용하여 입력하중을 추정하는 역해석 기법을 유한요소모델과 같은 해석적 모델을 알고 있는 경우와 주파수응답함수와 같은 실험적 모델을 알고 있는 경우에 대하여 제시하였으며 이때 발생되는 수학적 악조건의 특성을 규명하였다. 역해석시 발생되는 수학적 악조건은 시스템의 동강성행렬과 측정위치에 의해 결정되는 특성행렬의 조건수에 따라 결정되며 역해석기법을 공학문제에 적용하기 위하여는 특성행렬의 조건수가 낮아지도록 주자유도 및 측정점을 선택하여야 하고 특히 공진영역 및 반공진영역에서는 필연적으로 악조건이 발생됨을 알 수 있었다. 수학적 악조건의 특성을 명확히 규명하기 위하여 간단한 수치해석을 통하여 그 결과를 제시하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.75-78
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• 2005

In this paper, an experimental study on porous air bearing stiffness for ultra precision positioning system was performed. In general manufacturer provide bearing stiffness under specific air pressure, but the air pressure used in the field is different. Therefore it is necessary to know the stiffness of air bearing under the pressure used in the field. In order to know that, experimental device which can realize actual operating conditions was made. Using this device, static and dynamic stiffness of air bearing can be obtained. As a result, displacement error occurred around 1 $\mu$m at recommended load.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.137-147
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• 1995

The unbalance response analysis is one of the essential area in the forced vibration analysis of rotor-bearing systems. Local bearing parameters in rotor-bearing systems are the major sources which give rise to a difficulty in unbalance response computation due to the complicated dynamic properties such as rotational speed dependency and anisotropy. In the present paper, an efficient method for unbalance responses is proposed so as to easily take into account bearing parameters in computation. An exact matrix condensation procedure is proposed which enables the present method to compute unbalance responses by dealing with condensed, small matrices. The proposed method causes no errors even though the computation procedure is based on the small matrices condensed from the full matrices. The present method is illustrated through a numerical example and compared with the conventional method.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.266-274
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• 2002

The impact-echo test, which is to evaluate the integrity of concrete and masonry structures nondestructively, is an excellent method in the practical application. However, there are cases that the Impact-Echo testing nay result in the low reliability. In this study, the reliability of the Impact-Echo testing was investigated through the numerical simulation of the Impact-Echo testing. The finite element analysis and the analysis based on the dynamic stiffness matrix method was incorporated for the numerical simulation, in which the cases of a sandwiched shear stiffness, an incr＋easing or decreasing stiffness, and a homogeneous stiffness. Based on the results of the analysis were considered, this study proposed the approaches to Improve the reliability of the Impact-Echo testing.