• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.222-228
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• 2008

We conducted a dynamic analysis of an underwater test collector, which operates on extremely soft soil of deep-seafloor. The underwater test collector consists of nodule pick-up device, vehicle tracks, nodule crusher, loading frame and electric-electronic system. The weight of underwater test collector is about 8600 kg. The average normal pressure, that the underwater test collector supports, is about 6.0 kPa. The dynamic analysis model of underwater test collector is developed using commercial software RecurDyn-LM and Visual Fortran 90. A terramechanics model of extremely soft soil is implemented to the software based on user-written subroutine and applied to the dynamic analysis of the underwater test collector model. The dynamic responses of test collector are studied with respect to track velocities, terrain conditions, and coefficients of added mass and drag.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.2
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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.

• Journal of Korean Society of Forest Science
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• v.84 no.2
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• pp.218-225
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• 1995

In this paper, a mechanical analysis model for steep-slope log-skidding operations of a rubber-tired tractor is discussed and the applicability of the model is investigated. The model largely consists of mathematical analysis models for log drag, dynamic vehicle weight distributions and soil-vehicle traction. For the case study, a theoretical data set for log skidding operations is used in investigating the effect of the factors influencing the results of mechanical analysis or the productivity of skidding operations. The analyses include 1) the effect of log choking methods on tangential log-skidding force, 2) the effects of the change in travel speed and log load on the required input power to the wheels and 3) the log skidding performance of a two-wheel drive compared with that of a four-wheel drive.

• Journal of Korean Society of Transportation
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• v.32 no.5
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• pp.503-512
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• 2014

In this paper, various tire blow-out force experiment data were collected and analyzed to obtain approximate values of related coefficients such as rolling resistance, self-aligning torque, cornering stiffness, and radial stiffness for the analysis of the motion of vehicles with tire blow-outs. These coefficients related to tire blow-outs were input into a vehicle accident analysis program to simulate and examine the effects of tire blow-outs. Various configurations and velocities of vehicle collisions without tire blow-outs were also used as reference to establish collision events of vehicle collisions with tire blow-outs. For the events, the simulation analysis was performed and collision characteristics were obtained. Consideration of tire blow-outs or damages suggested in this study will greatly contribute to more reliable vehicle accident reconstructions.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.479-486
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• 2000

There has been recently an on-going effort in railway community to improve the dynamic performance of on-site railroad track with limited track possession time. In this paper, train running test lateral resistant force test and static/dynamic analyses are conducted before and after sprinkle of the ballast stabilizer in order to investigate the dynamic behaviors and parameters of the railroad track. Based upon the above results, effects of the stabilizer is verified, and a table for the track modulus representing on-site track condition and the methods to reduce the vibration and the transmitting forces of the ballasted track components to the infrastructures are suggested. It is thought that the suggestions made in this paper could be used as the preliminary data for the condition assessment and the maintenance of the track in the future.

• Journal of computational fluids engineering
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• v.19 no.2
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• pp.66-71
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• 2014

Aerodynamic design of a vehicle has very important meaning on the fuel economy, dynamic stability and the noise & vibration of a moving vehicle. In this study, the correlation of aerodynamic effect between two model vehicles moving inline on a road was studied with the basic SAE model vehicle. Drag and lift are two main physical forces acting on the vehicle and both of them directly effect on the fuel economy and driving stability of the vehicle. For the research, the distance between two vehicles is varied from 5m to 30m at the fixed vehicle speed, 100km/h and the side-wind was assumed to be zero. The main issue for this numerical research is on the understanding of the interaction forces; lift and drag between two vehicles formed inline. From the study, it was found that as the distance between two vehicles is closer, the drag force acting on both the front and rear vehicle decreases and the lift force has same trend for both vehicle. As the distance(D) is 5m, the drag of the front vehicle reduced 7.4% but 28.5% for the rear-side vehicle. As the distance is 30m, the drag of the rear vehicle is still reduced to 22% compared to the single driving.

• Journal of the Korean GEO-environmental Society
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• v.11 no.3
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• pp.23-32
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• 2010

In this study, Generally sandbag was used to reinforce slope or restore levee by using the in-situ material. To increase shear strength of sandbag, the Velcro system was effective for geosynthetic interface and make up for the weakness of shear strength between sandbag to sandbag. In this study, shear properties of geosynthetic-geosynthetic and geosynthetic-soil were evaluated from large scale direct shear tests. The cohesion and the angle of internal friction of each interface was evaluated. And laboratory model tests were performed to compare strength of reinforcement with strength of none reinforcement. As a result of this study, the cohesion and the angle of internal friction of each interface was increased, especially the cohesion was increased more than the angle of internal friction. Also according to the result of model test, the bearing capacity was increased by 20%.

• Journal of the Korean Geotechnical Society
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• v.34 no.2
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• pp.43-54
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• 2018

Underwater tracked vehicle is employed to perform underwater heavy works on saturated seafloor. When an underwater tracked vehicle travels on the seafloor, shearing action and ground settlement take place on the soil-track interface, which develops the soil thrust and soil resistance, respectively, and they restrict the tractive performance of an underwater tracked vehicle. Thus, unlike the paved road, underwater tracked vehicle performance does not solely rely on its engine thrust, but also on the soil-track interaction. This paper aimed at evaluating the tractive performance of an underwater tracked vehicle with respect to ground conditions (soil type, and relative density or consistency) and vehicle conditions (weight of vehicle, and geometry of track system), based on the soil-track interaction theory. The results showed that sandy ground and silty sandy ground generally provide sufficient tractions for an underwater tracked vehicle whereas tractive performance is very much restricted on clayey ground, especially for a heavy-weighted underwater tracked vehicle. Thus, it is concluded that an underwater tracked vehicle needs additional equipment to enhance the tractive performance on the clayey ground.

• International Journal of Highway Engineering
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• v.12 no.2
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• pp.17-23
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• 2010

Since the relatively stiff binder shows a higher tensile strength as well as higher rutting resistance, it is believed that the binder stiffness is an important factor for rutting and tensile strength of asphalt mixtures. The typical tensile property is measured by indirect tensile strength (ITS) test at $25^{\circ}C$ and the rutting resistance is most widely measured by wheel tracking (WT) test at $60^{\circ}C$. The deformation strength ($S_D$) is newly developed property to estimate rut resistance of asphalt concretes at $60^{\circ}C$. The ITS and $S_D$ are very simple to measure by static test techniques, but the WT is measured by repeated loading procedure which requires relatively longer time and more efforts. Since these three properties are highly dependent upon the binder stiffness, it may be possible to estimate one property from another. Therefore, this study investigate the possibility of estimating the rutting characteristics (measured by WT test) by ITS or $S_D$ test, and the ITS by $S_D$. Because of binder stiffness effect, in the WT estimation by ITS, a tendency was observed for the higher ITS mixture to have the lower rut depth, giving $R^2{\fallingdotseq}$0.6, on the average. The ITS estimation by $S_D$ showed $R^2{\fallingdotseq}$0.64, and the WT estimation by SD showed $R^2{\fallingdotseq}$0.84, which is highest correlation among the three. Therefore, it was concluded that there is relatively good possibility of estimating WT result by $S_D$, and even though $R^2$ is somewhat low, there is some correlation between WT and ITS.