• 한국정밀공학회지
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• 제12권3호
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• pp.101-109
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• 1995

Axisymmetric and quasi-static finite element analysis of an inflated tire rotating with constant angular velocity and contact to road has been performed. Centrifugal force effect was added to load stiffness matrix and equation of effective material properties were calculated by the Halpin-Tsai formulation. In this report, radial truck/bus tire was analyzed. It was inflated and rotated at speeds up to 140 km/h. Then, contact problem was performed to calculate stress-strain field of tire wiht flat rigid road under the load due to the self-weight of a vehicle. Significant changes of stress-strain field of tire were observed in the finite element analysis. Shear stress, strain and strain energy density were rapidly increased at the dege of #2 belt at freely rotating state. This concentrated stress and strain made belt edge sparation. Under the condition of flat riged road contact, strain energy density of #2 belt, carcass turn-up part were concentrated and bigger values than only freely rotation state. Therefore, dynamic behaivor of tire has to considered as design factors which are affected to belt edge separation and bead breakage.

• 한국소음진동공학회논문집
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• 제13권4호
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• pp.266-273
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• 2003

The purpose of this study is to obtain the effects of the parameters of the suspension system in railway rolling-stock for KT-23 type Passenger vehicle. According to the analysis and the small scale model car test. optimal condition was obtained for the stiffness ratio of secondary spring to primary spring of the suspension system and the mass ratio of the bogie frame to the car body. The analysis of the study shows that if the car body mass is increased or secondary stiffness Is lowered, the vertical vibration level is reduced and the passenger comfort can be improved. Especially, strong peaks are occurred in the frequencies corresponding to the rotational speed of driving axle and vehicle wheel. Hence, in order to obtain the dynamic characteristics through the small scale model car, the driving method of the vehicle on the test bench, rotational characteristics of the wheel and the natural modes of vehicle should be investigated and be modified.

• 한국도로학회논문집
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• 제13권2호
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• pp.1-8
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• 2011

본 연구의 목적은 중온화 첨가제(LEADCAP$^{(R)}$)를 사용한 중온 아스팔트 바인더의 노화 방법에 따른 물성 변화 특성을 평가하고자 하였다. 아스팔트 바인더의 노화 거동을 모사하기 위해 단기노화인 RFTO를 실시하였으며, 햇빛에 의한 자연 노화 거동을 알아보기 위해 자외선 경화기를 이용하여 자외선에 의한 열화거동을 모사하였다. 이러한 열화 중온 아스팔트 바인더의 역학적인 물성과 유변동학적인 특성을 시험하기 위해서 만능시험기(UTM)과 동적전단유동기를 이용하여 직접인장력과 유변동학적인 거동을 평가하였다. 또한, 열분석 장비를 이용하여 온도에 따른 중온 아스팔트 바인더의 특성을 평가하여, 자외선 노출에 따른 열화가 발생하여도 온도에 따른 물성 변화가 많이 발생하지 않음을 발견하였다. $70^{\circ}C$에서 중온화 첨가제가 첨가한 단기노화 중온 아스팔트 바인더의 경우, PG 등급에서의 고온 등급의 기준값을 만족함을 알 수 있었다. 또한 저온에서 중온 아스팔트 바인더의 인장 특성을 평가한 결과, 인장강도 향상과 함께 인장력이 증가됨을 알 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.590-595
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• 2007

It is important to predict the collision behavior of a train consist to improve its crashworthiness. To analyze crash behavior of train, four kinds of methods are mainly used so far. The first is method using multibody dynamics to predict the gross motion of the train set. The second uses 3D FE model to apply the section analysis method in order. The third is used to deduce design specification and evaluate the crashworhiness of a train by using 1D model. The last is to constitute 2D model to check overriding and coupling devices. The train evaluation procedures are so complex that it is difficult to understand or deal with. In this study, VTM for railway train was introduced to simplify the procedures. VTM involves 3D models, 1D models and dynamic components such as suspension and coupling. The method using hybrid concept model makes it possible to do all the things that are mentioned above. To analyze crash behavior tendency of VTM, the model was simulated and the simulation results were discussed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1032-1038
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• 2008

KTX train system is composed of TORNAD* network for transmitting information of train's internal equipments and OBCS which proceed information within train. OBCS of one trainset consisted of 28 equipments takes intelligent and dynamic composition according to equipment handling, train command and control flow. Each OBCS which is installed within trainset handle and supervise mutually action information about equipments, transmit it to driver to transmit information about train operation and preventive management. This mutual supervision and information transmission use KTX TORNAD* network system. TORNAD* network system is the one which is uniquely developped by GEC ALSTHOM, the KTX trainset manafacturing provider and this field is excluded from technical know-how transfer item. Through the research on analysis method of KTX TORNAD* system data structure which is operating on Seoul-Pusan Line, I hope that this thesis can contribute to train network system's standardization after applying it to improvement of train network system maintenance, enhancing quality of train service and applying it to future Korean rolling stock network system development.

• 대한기계학회논문집A
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• 제36권11호
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• pp.1413-1420
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• 2012

철도차량의 동적 거동 및 안정성 등을 예측하고 물리적인 특성을 이해하기 위하여 철도선진국인 영국, 프랑스, 일본 등에서는 축소모델 제작 및 시험하는 방법과 컴퓨터 시뮬레이션을 통하여 해석적으로 접근하는 방법이 사용되고 있다. 실물 규모의 동특성 시험은 대규모의 시험설비 구축에 따른 많은 비용과 시간의 소요, 그리고 시험 환경 설정의 어려움 등의 문제점이 발생하게 된다. 이러한 단점들을 극복하고자 상사법칙을 적용한 축소대차 모델을 이용하여 동적 시험 및 컴퓨터 시뮬레이션을 통한 해석적 연구를 수행하고 있다. 본 연구에서는 소형탈선시뮬레이터를 이용한 1/5 축소대차의 주행안정성 시험에서 신뢰성이 검증된 해석모델을 이용하여 주행안정성에 미치는 매개변수 중 주행속도, 차체 하중의 2가지 변수에 따른 1/5 축소대차의 주행안정성 해석을 수행하고, 그에 따른 동적특성을 검토하였다.

• 한국항만경제학회지
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• 제38권2호
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• pp.49-67
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• 2022

본 연구는 Diebold and Yilmaz (2012, 2014, 2016)의 분석방법을 적용하여 2007년 7월 19일부터 2022년 3월 31일까지 해상운임지수(BDI, BDTI, BCTI)에너지(원유, 천연가스, 석탄), 곡물(대두, 옥수수, 밀)을 대상으로 연계성을 분석하였다. 본 논문의 주요 분석결과는 다음과 같다. 첫째, 네트워크 분석 결과에 따르면 전체 분석기간의 경우 총 연계성은 20.43%로 측정되어, 해상운임지수와 상품가격 사이에 상호 연관성이 낮은 것으로 나타났다. 또한, 방향 연계성 결과를 살펴보면, 영향력이 가장 큰 변수는 옥수수로 나타났으며, 그 반대로 BDI가 가장 낮은 변수로 나타났다. 마지막으로 시기별로 구분하였을 때, COVID-19 기간에만 BCTI가 주도적인 역할을 하는 것으로 나타났다. 둘째, 표본이동분석결과에 따르면, 총 연계성이 금융위기, 무역전쟁, COVID-19 등과 같이 경제 상황의 변화와 특정 사건이 발생할 때 서로 간의 상호 연관성이 높은 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제30권6호
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• pp.679-698
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• 2008

On marine vessels, delicate instruments such as navigation radars are normally mounted on ship masts. However the vibrations at the top of mast where the radar is mounted often cause serious deterioration in radar-tracking resolution. The most serious problem is caused by the rotational vibrations at the top of mast that may be due to wind loading, inertial loading from ship rolling and base excitations induced by the running propeller. This paper presents a method of semi-active vibration control using magneto-rheological (MR) dampers to reduce the rotational vibration of the mast. In the study, the classical optimal control algorithm, the independent modal space control algorithm and the double input - single output fuzzy control algorithm are employed for the vibration control. As the phenomenological model of an MR damper is highly nonlinear, which is difficult to analyse, a back- propagation neural network is trained to emulate the inverse dynamic characteristics of the MR damper in the analysis. The trained neural network gives the required voltage for each MR damper based on the displacement, velocity and control force of the MR damper quickly. Numerical simulations show that the proposed control methods can effectively suppress the rotational vibrations at the top of mast.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.138-143
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• 1998

The continuous casting process has been adopted increasingly in recent years to save both energy and labor. It has experienced a rapid development in the production of semi-finished steel products, replacing the conventional route of ingot casting plus rolling. To achieve this good merit, however, more studies about a heat transfer mechanism between roll and slab are needed. So this paper shows the results of the deformation behavior of steel cast slabs, which are about the solidification and heat transfer. This study is used to prevent internal cracks of a slab in a bending and unbending zone. The value of moving strand shell bulging between two supporting rollers under ferrostatic pressure and slab-self weight has been computed in terms of creep and elastic-plasticity. The high strand distributions in solidified shell undergoes a series of bulging are calculated with boundary condition a very closed to continuous steel cast slabs productions.

• 한국자동차공학회논문집
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• 제18권2호
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• pp.56-60
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• 2010

Since the forming process involves the strain rate effect, a yield function considering the strain rate is indispensible to predict the accurate final blank shape in the forming simulation. One of the most widely used in the forming analysis is the Hill48 quadratic yield function due to its simplicity and low computing cost. In this paper, static and dynamic uni-axial tensile tests according to the loading direction have been carried out in order to measure the yield stress and the r-value. Based on the measured results, the Hill48 yield loci have been constructed, and their performance to describe the plastic anisotropy has been quantitatively evaluated. The Hill48 quadratic yield function has been modified using convex combination in order to achieve accurate approximation of anisotropy at the rolling and transverse direction.