• Journal of Biosystems Engineering
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• 제36권6호
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• pp.422-433
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• 2011

Market demand for hydro-mechanical transmission (HMT) for agricultural tractors has increased recently. To select a type of HMT satisfying design conditions, performance characteristics of 12 HMT types must be understood. This study was conducted to provide tractor engineers with a guideline to select the most appropriate HMT type for their design requirements. Characteristics on speed reduction ratio, power transmission efficiency, power regeneration, lock-up angular velocity, output torque ratio and torque ratio of planetary gear train axis of the 12 HMT types were investigated and presented as either formula or graphical forms. A guideline to select proper HMT type was also presented using 2 parameter: lock-up angular velocity (${\omega}_L$) and torque ratio of the planetary gear train axis. In addition, effect of gear ratio of the planetary gear train on the power transmission efficiency was investigated and a guideline to select the best gear ratio was also presented.

• Structural Engineering and Mechanics
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• 제71권6호
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• pp.699-712
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• 2019

The reinforced concrete lining of hydraulic pressure tunnels tends to crack under high inner water pressure (IWP), which results in the inner water exosmosis along cracks and involves typical hydro-mechanical interaction. This study aims at the development, validation and application of an indirect-coupled method to simulate the lining cracking process. Based on the concrete damage plasticity (CDP) model, the utility routine GETVRM and the user subroutine USDFLD in the finite element code ABAQUS is employed to calculate and adjust the secondary hydraulic conductivity according to the material damage and the plastic volume strain. The friction-contact method (FCM) is introduced to track the lining-rock interface behavior. Compared with the traditional node-shared method (NSM) model, the FCM model is more feasible to simulate the lining cracking process. The number of cracks and the reinforcement stress can be significantly reduced, which matches well with the observed results in engineering practices. Moreover, the damage evolution of reinforced concrete lining can be effectively slowed down. This numerical method provides an insight into the cracking process of reinforced concrete lining in hydraulic pressure tunnels.

• 터널과지하공간
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• 제12권4호
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• pp.291-303
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• 2002

본 연구에서는 삼차원 역학적 해석과 수리-역학 상호작용 해석에 동시에 적용할 수 있도록 불연속면자료를 이용하여 삼차원 블록을 만드는 프로그램을 개발하였다. 삼차원 블록의 역학적 해석을 위해 Shi가 개발한 이차원 불연속변형 해석의 이론을 삼차원으로 확장하여 프로그램을 개발하고 실제 블록에 적용하여 변위를 계산하였다 수리해석과 수리-역학적 상호작용 해석을 위해 기존의 이차원 불연속변형 해석의 수리-역학 상호작용 모델링 연구를 삼차원으로 확장하여 삼차원 불연속면을 고려한 수리-역학 상호작용해석을 실시하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제32권3호
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• pp.413-420
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• 2008

In order to improve the performance of cross-flow hydro turbine, detailed examination of the effect of the turbine configuration on the performance is needed necessarily. Therefore, this study is aimed to investigate the effect of blade angle on the performance of the cross-flow hydro turbine. Analysis of the turbine performance with the variation of the blade angle has been made by using a commercial CFD code. The results show that inlet and outlet angles of runner blade give considerable effect on the performance of the turbine. Pressure on the surface of the runner blade changes remarkably by the blade angle both at the Stages 1 and 2. Moreover, relatively small blade inlet angle is effective to produce higher value of output power. Recirculating flow in the runner passage causes remarkable hydraulic loss.

• Journal of Advanced Marine Engineering and Technology
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• 제36권7호
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• pp.902-909
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• 2012

This study is aimed to develop a new type of micro cross-flow hydro turbine which has very simple structure and relatively high efficiency. Micro eco cross-flow hydro turbine (ECFT) is proposed to apply in the ranges of very low and middle specific speeds in order to extend the operational range of the turbine. In order to not only obtain a basic data for a new design method of ECFT but also improve the turbine efficiency, experiments and CFD analysis on the performance and internal flow characteristics of the turbine model are conducted. According to the present study results, anti-recirculation block (ARB) and relatively wide turbine width with high flow rate improve the turbine efficiency.

• 대한전기학회논문지
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• 제45권2호
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• pp.294-300
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• 1996

In hydro-generator, a groundwall insulation of stator windings gradually deteriorates due to mechanical, thermal, electrical and environmental stresses. These stresses combine to result in loose windings, delamination of the stator insulation and/or electrical tracking of the endwinding, all of which can lead to stator insulation failures. Conventionally, off-line tests such as partial discharge measurement, DC/AC current and .DELTA.tan.delta. tests has been used for estimation of winding condition. However, off-line test requires large power supply and generator outage. In addition, major cause of insulation problems such as loose wedges and slot dischages may not be found with off-line diagnoses. This paper introduces the on-line partial discharge measurement techniques using frequency spectrum analyzer(FSA) for the generator stator windings. The experimental results from the UIAM #1 hydro-generator confirms a optimistic application of on-line generator diagnosis method as a reliable tool for evaluation of winding condition.

• 한국산림과학회지
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• 제108권4호
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• pp.562-573
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• 2019

국내 임목수확작업에 사용되고 있는 트랙터 기반 소형 타워야더는 소경재 생산을 목적으로 개발되었으며, 중대경재 수확 체제로 변화함에 따라 견인 성능의 개선이 필요하다. 이 연구는 동력 전달방식을 기존의 기계식에서 기계 유압식으로 개선하여 타워야더의 최대 견인력을 비교·분석하였으며, 트랙터 엔진속도, 유압식 동력 전달 기구의 압력을 변수로 두고 견인 성능 실험을 실시하였다. 실험 수준은 트랙터 엔진속도(1,200, 1,400, 1,600, 1,800, 2,000, 2,200 rpm) 6수준, 동력 전달 기구의 압력(4.9, 6.9, 8.8 MPa) 3수준으로 선정하였다. 기존의 경우 최대 견인력은 엔진 회전속도 757 rpm에서 15,146.6 N의 최대견인력을 발휘하였으나 개선된 타워야더는 엔진 회전속도 1,575 rpm에서 36,140 N의 최대 견인력이 나타나, 최대 견인력이 2.4배 증가되었다. 이에 따라 중대경재 위주의 목재수확 현장에서 작업이 가능할 것으로 판단된다. 또한 기존 장비를 재활용하여 성능 개선함으로써 견인력이 큰 집재장비의 신규 도입 및 운영에 필요한 비용을 줄일 수 있을 것으로 기대된다.

• 터널과지하공간
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• 제33권1호
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• pp.57-69
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• 2023

본 연구에서는 2차원 수리-역학적연계 개별요소모델링(DEM)을 사용하여 네델란드 그로닝엔(Groningen) 천연가스전 저류층의 유발지진을 모사하였다. 수치해석 코드는 ITASCA社의 상용프로그램인 PFC2D (Particle Flow Code 2D)를 사용하였으며 본 수치해석 연구에 적용하기 위해 수리-역학적 연계 모델 외 1) 비균질 저류층 압력분포 초기화, 2) 비선형 압력-시간이력 경계조건, 3) 국소 응력 분포 계산 등의 개별모듈을 추가개발, 적용하였다. 그로닝엔 가스전에 분포하는 복잡한 단층 형상을 포함하는 40 × 50 km² 크기의 2차원 모델을 생성하였고, 1960년부터 2020년까지 약 60년 동안의 가스생산, 즉 압 력저하로 인한 단층의 파괴거동을 모사하였다. 유발지진의 시공간적 발생을 수치해석모델로 재현하였고 그 발생 메커니즘을 규명하였다. 또한 저류층 압축으로부터 지표에서의 지반침하의 분포를 예측하였고 그로닝엔에서의 실측자료 사이에 유사성을 확인할 수 있었다. 이를 통해 본 연구에서 소개한 2차원 수리-역학적연계 개별요소모델링(DEM)의 복잡한 지질조건과 수리-역학적 연계 프로세스에 의한 단층거동을 구현할 수 있는 툴(tool)로서의 활용성을 확인하였다.

• 드라이브 ㆍ 컨트롤
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• 제17권2호
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• pp.19-27
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• 2020

The purpose of this study was to suggest design criteria for the HMT (hydro-mechanical transmission) of a 55 kW-class agricultural tractor, develop a simulation model, and evaluate its performance such as axle rotational speed, tractor speed, and power transmission efficiency. In this study, the HMT comprised a compound planetary gear and a HSU (hydro-static unit), and the compound planetary gear comprised two planetary gear sets. The HMT has three gear stages, and the maximum tractor speed was selected as 40 km/h. The simulation time was set at 2736 hours considering the lifetime of the tractor, and the simulation was performed for each gear stage at the engine-rated power conditions. As a result of the simulation, the axle rotational speeds for each gear stage were 39, 77, and 158 rpm, respectively. The range of tractor speed for each gear stage were 1.05-10.22 km/h, 10.74-20.17 km/h, and 20.70-41.40 km/h, respectively. The APE (absolute percentage gear) for the tractor's maximum speed between target value and simulation results were 2.20%, 0.85%, and 3.50%, respectively. Also, the power transmission efficiency for each gear stage were 0-75%, 72-81%, and 69-81%, respectively. The simulation results for the power transmission efficiency of the HMT were similar with the results of the previous research. This was a basic study on the development of the HMT for an agricultural tractor. In future studies, it is necessary to develop a tractor platform and evaluate the performance. The comparison between the simulation model and the HMT tractor should be performed.

• 한국자동차공학회논문집
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• 제16권1호
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• pp.86-92
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• 2008

Recently, the use of tubes in the manufacturing of the automobile parts has increased and therefore many automotive manufactures have tried to use hydro-forming technology. The hydro-forming technology may cause many advantages to automotive applications in terms of better structural integrity of the parts, lower cost from fewer part count, material saving, weight reduction, lower spring-back, improved strength and durability and design flexibility. In this study, the whole process of front engine cradle (or front sub-frame) parts development by tube hydro-forming using steel material having tensile strength of 440MPa grade is presented. At the part design stage, it requires feasibility study and process design aided by CAE (Computer Aided Design) to confirm hydro-formability in details. Effects of parameters such as internal pressure, axial feeding and geometry shape on automotive sub-frame by hydro-forming process were carefully investigated. Overall possibility of hydro-formable sub-frame parts could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of tube material on every forming step such as pre-bending, preforming and hydro-forming. At the die design stage, all the components of prototyping tools are designed and interference with press is examined from the point of geometry and thinning.