• Elastomers and Composites
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• 제52권3호
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• pp.216-223
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• 2017

The additive manufacturing technology, also called 3D printing, is growing fast. There are several methods for 3D printing. Fused deposition modeling (FDM) type 3D printing is the most popular method because it is simple and inexpensive. Moreover, it can be used for printing various thermoplastic materials. However, it contains the cooling of layered road and causes thermal shrinkage. Thermal shrinkage should be controlled to obtain high-quality products. In this study, temperature distribution and cooling behavior of a layered road with cooling are studied through computer simulation. The thermal shrinkage of the layered road was simulated using the calculated temperature distribution with time. Shape variation of the layered road was predicted as cooling proceeded. Stress between the bed and the layered road was also predicted.This stress was considered as the detaching stress of the layered road from the bed. The simulations were performed for various thermal conductivities and temperatures of the layered road, bed temperature, and chamber temperature of a 3D printer. The simulation results provide detailed information about the layered road for FDM type 3D printing under operational conditions.

• 한국기계가공학회지
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• 제21권3호
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• pp.29-35
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• 2022

When a vehicle is driven off a road surface, the deformations of the road surface and tire are combined. Consequently, the dynamic behavior of wheel movement becomes difficult to predict and control. Herein, we propose a tire test bed to capture the dynamic behavior of tires moving on sand and soil. Based on this study, it is discovered that the slip rate can be controlled, and the vertical force can be measured using a load cell. The test results show that this test bed can be useful for capturing the dynamic behavior of the tire and validating dynamic simulations. In fact, the tire test bed developed in this study can be used to verify the results of computer simulations. In addition, it can be used for basic experiments pertaining to the speed control of unmanned autonomous vehicles.

• 자동차안전학회지
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• 제14권1호
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• pp.6-13
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• 2022

The Ministry of Land, Infrastructure and Transport (MoLIT) and the Korean Automobile Testing and Research Institute (KATRI) are supporting the development of Lv.3 automated vehicle (hereinafter, AV) technology by constructing an automated driving pilot city (as known as K-City) equipped with total 5 evaluation environments (urban, motorway, suburban, community road, and autonomous parking facility) which is a test bed exclusively for AV (2017~2018). An upgrade project is in a progress to materialize harsh environments such as bad weather (rain, fog, etc.) and reproduction of communication jamming (GPS blocking, etc.) with the purpose of supporting the development of Lv.4 connected & automated vehicle (hereinafter, CAV) technology (2019~2022). We intend to proactively establish a national level standard for CAV test-bed and test road requirements, test method, etc. for establishment of a road map for the construction of the test bed which is being promoted step by step and analyze and, when required, benchmark the case of China that has announced and is utilizing it. Through this, we plan to define standardized requirements (evaluation facility, evaluation system, etc.) on the test bed for the development of Lv.4/4+ CAV technology and utilize the same for the design and construction of a test bed, establishment of a road map for the construction of a real car-based test environment related to the support for autonomous driving service substantiation, etc. through provision of an evaluation environment utilizing K-City, and the establishment of a K-City upgrade strategies, etc.

• 한국환경복원기술학회지
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• 제2권3호
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• pp.83-92
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• 1999

To investigate the influence of forest road characteristics and site conditions on the stability of forest-road in granite area, four forest roads had been selected in Kyongbuk regions. The total of 13 road characteristic variables were evaluated by the discriminant analysis. The factors influencing the stability of forest road were bed rock, slope length, coverage, hardness, side-ditch erosion and road width. But aspect and soil texture were not significant for the stability in this area. In the correlation between forest environment and road structure, hardness and bed rock was highly significant in stability group, and coverage and side-ditch erosion was highly significant in instability group. 75 of 175 segments were instable whereas the others were stable. The centroids value by discriminant function in the stability and instability were estimated to 3.0585 and -1.9116, respectively. The stability criterion of forest road was discriminated from the centroids value of the each group. The main factors contributing the stability of forest road were significant in order of side-ditch erosion, coverage, soil texture, elevation, gradient, slope length and construction year. The prediction rate of discriminant function for stability evaluation of forest road was as high as 97.44%. In conclusion, the forest road structure factors such as length, coverage and slope gradient were controlled by construction techniques. If the factors like those should be considered in design, construction and forest road management, the stability of forest road may increase more. And also, it is necessary to take slope protection measures like small terraces and retaining walls for stability of cut slope.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1542-1549
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• 2009

The function of subgrade in the railway is to support track load on the subgrade as well as train load. Unlike the traditional railway, the uppermost subgrade layer in the Gyeongbu high speed railway was constructed as the reinforced road bed. The reinforced road bed comprises sub-ballast in the upper part and grade ballast in the lower part. The filling material such as soil and rocks in the subgrade can be settled by consolidation of original ground, compression due to self weight, plastic displacement due to train operation, and unequal settlement due to embankment material or improper compaction, therefore many efforts have been given for sufficient compaction and use of proper filling materials in the construction stage. The purpose of this study is to investigate the deformation state of subgrade in the Gyeongbu high speed railway. The investigation on the subgrade settlement was performed by choosing representative sections suspected to be settled based on the previous GPR test results and track maintenance history, measuring the settlement for some time period after installing settlement measuring instruments on and under the reinforced road bed. and analyzing the long-term subgrade settlement data from monitoring system which was installed at the construction stage of the high speed railway.

• 한국지반환경공학회 논문집
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• 제24권1호
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• pp.37-44
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• 2023

본 연구에서는 도로의 건설 시간 및 유지관리 비용을 단축하기 위하여 제안된 지속가능한 장수명 모듈러 도로시스템의 하부구조인 지지 모듈러의 성능을 평가하였다. 하부 곡선면을 가진 Cross-Beam 형태의 지지 모듈러 4개로 구성된 모듈러 도로시스템을 Test-bed에 시공하였다. 6개의 하중계와 8개의 변위계를 중앙부 2개 Cross-Beam 형태의 지지 모듈러에 설치하였다. 2개의 하중, 50kN, 100kN을 도로 포장슬래브 15개 지점에 재하하여 모듈러 도로시스템에서 발생하는 하중 및 변위를 측정하였다. 측정된 변위들은 1mm 미만으로 실제 도로의 안정성에 문제가 없을 것으로 판단된다. 현장실험에서 적용된 2개의 재하 하중들과 측정된 하중값들을 비교해 보았을 때 하부 지반에 전달되는 하중은 매우 작은 것으로 판단된다. 지지 모듈러를 가진 모듈러 도로 시스템을 실제 도로현장에 적용 가능한 것으로 판단된다.

• 한국ITS학회 논문지
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• 제15권4호
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• pp.115-128
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• 2016

전 세계적으로 도로 상에서의 교통사고를 줄이고 교통 효율을 향상시키기 위한 많은 연구가 수행되어 왔으며, 최근에는 특히 C-ITS(Cooperative Intelligent Transportation System, 협력형 지능형교통체계) 기술을 기반으로 한 연구가 활발히 진행되고 있다. C-ITS 기술의 핵심은 인프라, 차량, 사람 등 도로시스템을 구성하는 요소들이 서로 간에 정보를 공유하고 재생성함으로써 도로안전 및 교통효율의 향상을 도모하는 것이며, 이를 위해 차량용 무선통신기술인 V2X(Vehicle-to-X) 통신기술이 적용되고 있다. 국내에서는 스마트하이웨이 연구를 통해 V2X 통신기술에 대한 연구가 진행되어 왔으며, 실제 고속도로 환경에서의 기술성능을 검증하기 위해 테스트베드를 구축하여 운영하고 있다. 본 논문에서는 스마트하이웨이 테스트베드에 대해 간략히 소개하고, 테스트베드 상에서의 성능 분석 절차 및 결과에 대해 기술한다.

• International Journal of Railway
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• 제2권4호
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• pp.180-186
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• 2009

High speed railway challenge the design, construction and maintaining of traditional railway, many traditional design concepts have been changed. Transition of railway and bridge has two main problems. one is that different lines have different ability of resisting distortion in area of trial load, which was known that problem of smooth transition of stiffness, the other is that differential settlement between artificial structure and earth structure cause bending of railway. The two problems have effect on train moving. The principle of processing transition of railway and bridge is same in world, but it is difficult to find relationship between design standard of transition, vehicle performance, line standard, design speed and so on form documentation and data reports. Based on mechanics, the paper analyzed dynamic performance of transition of high speed railway, studied various rough elements which is effective to train moving, built mathematical model of interaction of train and transition of high speed railway and developed numerical simulation software. In various different work conditions, we did great quantity of numerical simulation, comprehensive analysis and performance analysis.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1542-1549
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• 2011

The Transitional zone between bridge abutment and earthwork is one of the representative vulnerable zones in railway where differential settlements may take place due to the different supportive stiffness. Although transitional zones are managed with stricter standards than those of the other earthwork zones either in the design and construction stages, it is very difficult to prevent differential settlement perfectly. A three-dimensional numerical analyses were performed by applying train moving load in this study. The analytical model including abutments and earthwork zones was constituted with rail, sleepers, track concrete layer (TCL), hydraulic stabilized base (HSB), reinforced road bed, and road bed using railway and road base structure. The clamp connecting the rail and sleeper were also modeled as the element with spring coefficient. The train wheel is modeled in the actual size and moved on the rail with 300 km/hr speed. The deformation characteristics at each point of the rail and the ground were considered in detail when moving the train wheel. The analysis results were compared with those from the two-dimensional analysis without considering moving load. The research results show that displacement and stress were greater in the three-dimensional analysis than in other analyses, and the three-dimensional analysis with moving load should be performed to evaluate railway performance.

• Journal of Mechanical Science and Technology
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• 제15권9호
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• pp.1248-1256
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• 2001

In this study, a test bed for vehicle longitudinal control is developed using a chassis dynamometer and real time 3-D graphics. The proposed test bed system consists of a chassis dynamometer on which test vehicle can run longitudinally, a video system that shows virtual driver view, and computers that control the test vehicle and realize the real time 3-D graphics. The purpose of the proposed system is to test vehicle longitudinal control and warning algorithms such as Adaptive Cruise Control(ACC), stop and go systems, and collision warning systems. For acceleration and deceleration situations which only need throttle movements, a vehicle longitudinal spacing control algorithm has been tested on the test bed. The spacing control algorithm has been designed based on sliding mode control and road grade estimation scheme which utilizes the vehicle engine torque map and gear shift information.