• Tribology and Lubricants
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• 제21권6호
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• pp.249-255
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• 2005

In this paper, the friction characteristic of engine bearings has been analyzed in terms of a friction loss power, a minimum film thickness and an oil film pressure. This analysis has been focused on the fuel economy improvement with a low viscosity engine oil such as SAE 0W-40, which is used for a friction loss reduction and increased for a Diesel fuel economy. The friction loss power, the minimum oil film thickness and oil film pressure distribution for plain bearings of a Diesel engine are analyzed using an AVL's EXCITE program with a conventional engine oils of SAE 5W-40 and 10W-40, and a low viscosity engine oil of SAE 0W-40. The computed results indicate that a viscosity of engine oils is closely related to the friction loss power and the decreased minimum film thickness in which is a key parameter of a load carrying capacity of an oil film pressure distribution. When the low viscosity engine oil is supplied to engine bearings, it does not affect to the formation of a minimum oil film thickness. But the friction loss power has been significantly affected by low viscosity engine oil at a low operating temperature of 0. Based on the FEM computed results, the low viscosity engine oil at a low temperature range will be an important factor for an improvement of the fuel economy improvement.

• Steel and Composite Structures
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• 제26권4호
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• pp.439-452
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• 2018

This paper presents experimental and numerical study on buckling behaviors and hysteretic performance of Class 1 H-shaped steel beam subjected to cyclic pure bending within the scope of ultra-low cycle fatigue (ULCF). A loading device was designed to achieve the pure bending loading condition and 4 H-shaped specimens with a small width-to-thickness ratio were tested under 4 different loading histories. The emphasis of this work is on the impacts induced by local buckling and subsequent ductile fracture. The experimental and numerical results indicate that the specimen failure is mainly induced by elasto-plastic local buckling, and is closely correlated with the plastic straining history. Compared with monotonic loading, the elasto-plastic local buckling can occur at a much smaller displacement amplitude due to a number of preceding plastic reversals with relative small strain amplitudes, which is mainly correlated with decreasing tangent modulus of the material under cyclic straining. Ductile fracture is found to be a secondary factor leading to deterioration of the load-carrying capacity. In addition, a new ULCF life evaluation method is proposed for the specimens using the concept of energy decomposition, where the cumulative plastic energy is classified into two categories as isotropic hardening and kinematic hardening correlated. A linear correlation between the two energies is found and formulated, which compares well with the experimental results.

• Steel and Composite Structures
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• 제12권5호
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• pp.445-464
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• 2012

In order to evaluate the dynamic behavior of passive energy dissipation system, two steps need to be considered for prediction of structural response in the presence of ductile element in an off-centre bracing system. The first is a detailed analysis of the proposed ductile element and the second is the effect of this ductile element on an off-centre bracing system. The use of ductile bracing system is expanding in steel structures in order to increase the force reduction factor. Therefore, regarding the nonlinear behavior of steel material used in an off-centre bracing systems and using ductile element in OBS bracing systems, the seismic evaluation of the mentioned systems seems to be necessary. This paper aims to study linear and nonlinear behavior of steel frames with off-centre bracing system and ductile element, in order to get the best position of these bracing elements. To achieve this purpose, the modeling has been done with ANSYS software. The optimum eccentricity has been obtained by modeling three steel frames with different eccentricities and evaluating the results of them. The analytical results showed that the model OBS-C with 0.3 eccentricities has higher performance among the models.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.974-981
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• 2005

Because general laboratory tests for sand compaction pile method including unit-cell test device have fixed outside diameter, as area replacement ratio increase, diameter of sand pile increase. These condition can bring about overestimation of stiffness of composite ground. In addition, existing large soil box which consist of bellows type loading plate can occur serious mistake in checking the amount of drained water because there are additional drainage along the inside wall in device. Overcoming these shortcoming, this paper developed modified large scale soil box consist of piston type load plate. In this study, using this device, series of modified large scale soil box tests were performed, and investigated the settlement and stress transportation characteristics with area replacement ratio in sand compaction pile method.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.50-57
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• 2010

Various installation faults may lie in fasteners in the construction of a direct-fixation track by the top-down method. At an extreme, they may cause excessive interaction between the train and track, compromise the running safety of the train, and cause damage to the track components. Therefore, the faults need to be kept within the allowable level through an investigation of their effects on the interactions between the train and track. In this study, the vertical dynamic stiffness of fasteners in installation faults was measured based on the dynamic stiffness test by means of an experimental apparatus that was devised to feasibly reproduce gap faults. This study proposes an effective analytical model for a train-track interaction system in which most elements, except the nonlinear wheel-rail contact and some components that behave bi-linearly, exhibit linear behavior. To investigate the effect of the behavior of fasteners in gap faults in a direct-fixation track on the vehicle and track, vehicle-track interaction analyses were carried out, targeting key review parameters such as the wheel load reduction factor, vertical rail displacement, rail bending stress, and mean stress of the elastomer. From the results, it was noted that the gap faults in the concrete bearing surface of a direct-fixation track need to be limited for the sake of the long-term durability of the elastomer than for the running safety of the train or the structural safety of the track.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.804-811
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• 2015

The presence of responsive loads in the promising active distribution networks (ADNs) would definitely affect the power system problems such as distributed generations (DGs) studies. Hence, an optimal procedure is proposed herein which takes into account the simultaneous placement of DGs and smart meters (SMs) in ADNs. SMs are taken into consideration for the sake of successful implementing of demand response programs (DRPs) such as direct load control (DLC) with end-side consumers. Seeking to power loss minimization, the optimization procedure is tackled with genetic algorithm (GA) and tested thoroughly on 69-bus distribution test system. Different scenarios including variations in the number of DG units, adaptive power factor (APF) mode for DGs to support reactive power, and individual or simultaneous placing of DGs and SMs have been established and interrogated in depth. The obtained results certify the considerable effect of DRPs and APF mode in determining the optimal size and site of DGs to be connected in ADN resulting to the lowest value of power losses as well.

• Journal of Advanced Marine Engineering and Technology
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• 제22권2호
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• pp.248-256
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• 1998

The effects of fuel injection system on the performance in a V8-type diesel engine was stuided in this paper. Fuel injection system is important factor which influence the engine performance and exhaust emission bcasuse the properties in the injected fuel depend on the atomization characteristics. In this study using diesel engine of 17.7:1 compression ration the engine performance and exhaust emission are measured experimentally according to 1000, 1400, 2200rpm in the full-load conditions. The chosen parameters for the major system are such diameter shape of combustion chamber and intake system. The results are as follows: As the nozzle hole diameter and injection angle become smaller and as the injection timing gets advanced the fuel consumption and concentration of smoke are decreasing whereas concentration of $NO_{x}$ is increasing. Andconcentration of $NO_{x}$ is increasing in accordance with the increase of injection pipe diameter and nozzle protrusion. Also it is shown that re-entrant type combustion chamber is more effective than that of toroidal type in the improvement of $NO_{x}$ reduction.

• 전력전자학회논문지
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• 제5권2호
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• pp.176-183
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• 2000

본 논문에서는 단일 스위치 3상 승압형 컨버터 입력전류의 왜형을 개선하기 위한 6고조파 주입 PWM 방식이 제안디었다. 주기적인 6고조파 전압이 한 스위칭 사이클 내에 컨버터 스위치의 듀비티를 가변하도록 제어회로에 주입되었다. 그 결과 입력 상전류는 입력전압을 따라가고 거의 1에 가까운 역률을 얻었다. 실험결과는 3상 입력 AC 140∼220V, 400V∼6kW 저항부하와 3상 AC 220V, 비선형 부하인 CO2 아크 용접기에 의하여 입증하였다.

• 펄프종이기술
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• 제40권3호
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• pp.42-47
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• 2008

For the purpose of reduction of production cost in the industrial papermaking process, the use of waste paper has been more and more increased as a fibrous raw material, and the closed system of white water became closed more than ever. "Scum" indicates the floated sludge by a flotation during primary wastewater treatment process in paper mills. If the scum is used as the raw material, it could reduce both the raw material and solid waste treatment cost with even small quantity. In this study, the element survey and the toxicity measurement was carried out for recycling scum. A load factor of stock preparation process in paper mills was measured by somerville screen. Physical properties of paper sheet containing the accepted scum from the stock of AOCC or KOCC were evaluated. The result of this study shows that recycling scum has potential to be used in paper making system. It also might be able to reduce the required energy used by the pressing or drainage process, the raw material cost, and solid waste treatment cost due to the recycling of scum.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.129-137
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• 2000

The powertrain is an important factor for the interior and exterior noise behavior of the vehicle Thus, the noise vibration and harshness(NVH) behavior of an engine is becoming a major target of the powertrain development. This paper describes the analyses with the aim to reduce the vibration and noise of an advanced inline 4-cylinder diesel engine block by use of CAE methods. The characteristics of an engine block as a main excitation source of car interior noise is studied. Particularly, The effect of balance shaft to reduce the 2nd order engine excitation force is calculated by forced vibration and radiated noise analysis. The engine exitation forces are obtained under real operating conditions. It is shown that the reduction of vibration and noise level by adapting blancing shaft is well predicted and rediated noise is directly related to the surface velocity of engine block.