• 한국소음진동공학회논문집
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• 제23권5호
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• pp.431-437
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• 2013

Measured acoustic signal from operating high speed train contains frequency change called doppler shift due to its motion. To avoid this doppler shift wind tunnel test is required. But scaledown of model can cause change of source characteristics. And measurements using some part of train cannot reproduce real flow condition. The best way to recognize real noise source characteristics is measurement from operating high speed train but doppler shift makes it hard. So, we developed simple dedopplerization technique for one microphone and applied to field test data of high speed train. Through this, we could capture real frequency of noise from operating high speed train.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.647-652
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• 2001

A noise reduction of noise barrier for high speed train was measured by using scale down model test. A selected types of noise barriers were simple vertical barrier, interference type barrier with plate, interference type barrier with cylindrical pipes. On experiment, in order to make similar present test lane condition, reduced train model and multiple noise sources were considered. As a result. interference type noise barrier with cylindrical pipes is most effective than other barriers. A present height of noise barrier which is established in a test lane is not high enough for reducing patograph noise.

• 한국자동차공학회논문집
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• 제24권2호
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• pp.198-204
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• 2016

In this study, a wind tunnel test was conducted to measure the aerodynamic characteristics of a streamline-designed high-speed bus with the change of wind direction and speed and the result is compared with the aerodynamic performance of a commercialized high-speed bus model (Model-0) manufactured by Zyle Daewoo Bus Corp. Aerodynamic performance of the existing rear-spoiler was tested to prove its aerodynamic effect on the test model bus. From the study, it was found that 24.6 % of the total drag of the original bus model (Model-0) was reduced on the streamline-designed model bus(model-1) without the rear-spoiler but only 14.3 % of the total drag was reduced with the spoiler on the streamlined model bus. It means that the rear spoiler does not work properly with the streamlined model bus (model-1) and should be noted that an optimum design of a rear-spoiler of a vehicle is important to reduce the induced pressure drag and increase the driving stability of a vehicle against yaw motion. The experimental outcome was also compared to the previous numerical research result to evaluate the reliability of the numerical algorithm of the aerodynamic performance analysis of a vehicle. The error rate (%) of the numerical result to the experimental output is about 5.4 % and it is due to the simplified body configuration of the numerical model bus. The drag increases at the higher yaw angle because the transparent frontal area of the model vehicle increases and the downward force increases with the yaw angle as well. It has a positive effect to the driving stability of the vehicle but the moderated downward force should be kept for the fuel economy of a vehicle.

• 소성∙가공
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• 제13권6호
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• pp.528-534
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• 2004

In order to find the effect of lubricant viscosity, tool geometry, forming speed, and sheet material properties on the friction in the sheet metal forming, friction tests were performed. Friction test results show that as the lubricant viscosity becomes lower, the friction coefficient is higher. When surface roughness is extremely low or high, the friction coefficient is high. The bigger die corner radii and punch speed are, the smaller is the friction coefficient. From the experimental observation, the friction model which is the mathematical expression of friction coefficient in terms of lubricant viscosity, roughness and hardness of sheet surface, punch corner radius, and punch speed is constructed. By comparing the punch load found by FEM using the proposed friction model with that obtained from the experiment in 2-D stretch forming, the validity and accuracy of the friction model are demonstrated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.1232-1240
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• 2001

In this study. a computer simulation of the Korean High Speed Prototype Test Train was performed to investigate the dynamic behavior(running stability. safety and comfort) in detail design process. The simulation model which was prepared by ADAMS/Rail V10.l consists of power car and middle car assembly (2 motorized cars ＋ 3 trailer cars). The nonlinear analysis takes into account the full vehicle model including wheel/rail contact and the influence of disturbed track. Throughout the dynamic calculation of KHST on the straight and the curved track. accelerations in car body. ride comforts and wheel rail forces were investigated.

• Structural Engineering and Mechanics
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• 제85권2호
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• pp.265-274
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• 2023

The spherical steel bearings (SSBs) has been gradually replaced traditional rubber bearings and extensively applied to high-speed railway (HSR) bridges in China, due to their durability and serviceability. Nevertheless, SSB is generally simplified to the ordinary constraints in the finite element model, which cannot reflect its detailed mechanical characteristics, especially its seismic performance. To provide a more precisely simulation, an innovative and simplified finite element simulation method is proposed and the combined element group is developed in ANSYS. The primary parameters were determined by means of the performance test of SSB. The finite element model of SSB applied to a single-span HSR simply supported girder bridge was established through the proposed method. The seismic performance of the SSB was further investigated. A shake table test was conducted to evaluate the accuracy of the proposed simulation method. It is found that the numerical results could have a good agreement with the experiment, namely, the proposed method is feasible and efficient.

• 한국해양공학회지
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• 제30권2호
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• pp.69-74
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• 2016

A new wave-piercing-type high-speed planing boat without a chine was developed, and its basic performance was investigated in a model test, including the resistance, trim, and sinkage. The maximum speed of the developed ship was 35 knots. The hull form was developed by combining a VSV (very slender vessel) and TH (transonic hull), which have large deadrise angles at the bow. The main dimensions were estimated by a statistical approach using actual ship data. The effect of a side fin attached at the stern near the water line was investigated from a resistance point of view. It was found that the developed hull form showed the possibility of a new concept for a high-speed planing hull without a chine, and the side fin played an important role in increasing the resistance performance by controlling the trim and sinkage in the high-speed range.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1874-1880
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• 2011

In this paper, sensitivity analysis of the pantograph for the high-speed Train was conducted using finite element analysis method. Dynamic interaction of catenary-pantograph model was simulated by using a commercial finite element analysis software, SAMCEF. Pantograph was assumed to be three degree of freedom mass-spring-damper model and the pre-sag of the contact and messenger wire was implemented due to gravity. The span data of the actual high-speed line and specification of pantograph for high-speed train was applied in the analysis model, respectively. The reliability of the simulation model is verified by comparing the contact force results of simulation and test. Through the simulation, mean contact force and its deviation was evaluated and then sensitivity of the pantograph was analyzed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 추계학술대회 논문집
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• pp.179-186
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• 2001

As the freight traffic becomes heavier, the high speed of existing freight cars is essential instead of the construction of a new railway. The high speed can be achieved by the design modifications of the freight bogie. In this paper, an analytical model of freight bogie including the lateral force between rail and the flange of wheel is developed to decide the critical speed, which activates a hunting motion and tells the running safety of freight bogie. The dynamic responses of the analytical model were compared with an experimental data from a running test of a freight bogie and showed good agreements between them. The analytical model is used to find the design modifications of the freight bogie by parameter studies. The results show that the reduction of wheelset mass ratio and the increase of the axle distance of the freight bogie can increase the critical speed, but the primary lateral stiffness has little effects on the critical speed. And this also study shows that smaller wheel conicity deteriorates the running safety of the freight car, which means the overhauling of the wheel of freight bogie should be done regularly.

• Journal of Advanced Marine Engineering and Technology
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• 제38권10호
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• pp.1217-1224
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• 2014

This paper provides a practical scaling method to solve an old problem for scaling and developing the speed and resistance of a model to full-scale submarine in fully submerged underwater test. In every experimental test in towing tank, water tunnel and wind tunnel, in the first step, the speed of a model should be scaled to the full-scale vessel (ship or submarine). In the second step, the obtained resistance of the model should be developed. For submarine, there are two modes of movement: surface and submerged mode. There is no matter in surface mode because, according to Froude's law, the ratio of speed of the model to the full-scale vessel is proportional to the square root of lengths (length of the model on the length of the vessel). This leads to a reasonable speed and is not so much for the model that is applicable in the laboratory. The main problem is in submerged mode (fully submerged) that there isn't surface wave effect and therefore, Froude's law couldn't be used. Reynold's similarity is actually impossible to implement because it leads to very high speeds of the model that is impossible in a laboratory and inside the water. According to Reynold's similarity, the ratio of speed of the model to the full-scale vessel is proportional to the ratio of the full-scale length to the model length that leads to a too high speed. This paper proves that there is no need for exact Reynold's similarity because after a special Reynolds, resistance coefficient remains constant. Therefore, there is not compulsion for high speeds of the model. For proving this finding, three groups of results are presented: two cases are based on CFD method, and one case is based on the model test in towing tank. All these three results are presented for three different shapes that can show; this finding is independent of the shapes and geometries. For CFD method, Flow Vision software has been used.