• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.91-98
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• 2018

A numerical investigation of stage separation behavior of a two-body vehicle focusing on its flow characteristics is carried out. For this simulation, the separation of a booster from a vehicle is modeled using a chimera grid system and calculated with commercial code, $CFD-FASTRAN^{TM}$. Consideration of spring force, gravity and relative acceleration of a booster is the essential factor of a realistic simulation. In this study, it is validated that the booster separation time decreases with an increase in flight Mach number and angle of attack. In view of results thus far achieved, it is expected that the dynamics modeling and boundary condition set-up applied in this study will be useful for estimating safe stage separation and event sequencing of flight tests.

• Earthquakes and Structures
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• v.26 no.4
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• pp.251-259
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• 2024

In this paper, the thermal post-buckling behavior of graphene platelets reinforced metal foams (GPLRMFs) plate with initial geometric imperfections on nonlinear elastic foundations are studied. First, the governing equation is derived based on the first-order shear deformation theory (FSDT) of plate. To obtain a single equation that only contains deflection, the Galerkin principle is employed to solve the governing equation. Subsequently, a comparative analysis was conducted with existing literature, thereby verifying the correctness and reliability of this paper. Finally, considering three GPLs distribution types (GPL-A, GPL-B, and GPL-C) of plates, the effects of initial geometric imperfections, foam distribution types, foam coefficients, GPLs weight fraction, temperature changes, and elastic foundation stiffness on the thermal post-buckling characteristics of the plates were investigated. The results show that the GPL-A distribution pattern exhibits the best buckling resistance. And with the foam coefficient (GPLs weight fraction, elastic foundation stiffness) increases, the deflection change of the plate under thermal load becomes smaller. On the contrary, when the initial geometric imperfection (temperature change) increases, the thermal buckling deflection increases. According to the current research situation, the results of this article can play an important role in the thermal stability analysis of GPLRMFs plates.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.149-156
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• 2005

In this paper, the VR(Virtual Reality) simulation system is developed to analyze driver's perceptive response on the ASV(Advanced Safety Vehicle). The ASV is the vehicle of next generation equipped with various warning systems. For the purpose, the VR simulation system consists of VR database, vehicle dynamic model, graphic/sound system, and driving system. The VR database which generates 3D graphic and sound information is organized for the driving reality. Mathematical models of vehicle dynamic analysis are constructed to represent the dynamic behavior of a vehicle. The driving system and the graphic/sound system provide a driver with the operation of a vehicle and the feedback of a driving situation. Also, the real-time simulation algorithm synchronizes the vehicle dynamic model with the VR database. To check the validity of the developed system, a simple scenario is applied to investigate driver's perceptive response time and vehicle acceleration on an emergency situation. It is confirmed that the proposed system is useful and helpful to design the FVCWS(Forward Vehicle Collision Warning System).

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.183-190
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• 2005

During normal operating conditions, a motor vehicle is constantly subjected to a variety of forces, which can adversely affect its straight-ahead motion performance. These forces can originate both from external sources such as wind and road and from on-board sources such as tires, suspension, and chassis configuration. One of the effects of these disturbances is the phenomenon of vehicle lateral-drift during straight-ahead motion. This paper examines the effects of road crown, tires, and suspension on vehicle straight-ahead motion. The results of experimental studies into the effects of these on-board and external disturbances are extremely sensitive to small changes in test conditions and are therefore difficult to guarantee repeatability. This study was therefore conducted by means of computer simulation using a full vehicle model. The purpose of this paper is to gain further understanding of the straight-ahead maneuver from simulation results, some aspects of which may not be obtainable from experimental study. This paper also aims to clarify some of the disputable arguments on the theories of vehicle straight-ahead motion found in the literature. Tire residual aligning torque, road crown angle, scrub radius and caster angle in suspension geometry, were selected as the study variables. The effects of these variables on straight-ahead motion were evaluated from the straight-ahead motion simulation results during a 100m run in free control mode. Examination of vehicle behavior during straight-ahead motion under a fixed control mode was also carried out in order to evaluate the validity of several disputable arguments on vehicle pull theory, found in the literature. Finally, qualitative comparisons between the simulation results and the test results were made to support the validity of the simulation results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.92-97
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• 2012

In the present the usage of bicycle has increased steeply due to well-being and convenient way of movement. In car to bicycle accident, the throw distance of bicycle is very important factor for estimating collision situation. In this study, simulations and collision tests in actual car to bicycle were executed for obtaining throw distance of bicycle. The simulations were executed by PC-CRASHTM s/w with vehicle of sedan type. Sand bags were used for the behavior of bicyclist instead of dummy and factors considered were vehicle velocity, the crashed angles and part of bicycle to vehicle, and bicycle was adult type. From the results, the throw distances of tire collision of 00 was longer than that of 450 tire crash, and the throw distances of 900 frame crash were longer than those of 450 frame crash. With based on actual crash tests and simulations, restitution coefficient of between vehicle and bicycle was estimated as 0.1. Finally the increaser vehicle velocity the longer the throw distances of bicycle and the simulation results were relatively good agreement to the results of experiment.

• Journal of Drive and Control
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• v.9 no.4
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• pp.8-13
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• 2012

Recently, researches about the eco-friendly vehicles such as hybrid electric vehicle, fuel cell vehicle and electric vehicle have been actively carried out. The regenerative braking system is a key technology to improve the vehicle energy utilization efficiency because it transforms the kinetic energy to the electric energy through the electric motor. This new braking system requires cooperative control between electric controlled brake and regenerative brake. Therefore, it is necessary to establish fault-diagnosis and fail-safe evaluation criteria to secure reliability of the regenerative braking system. In this paper, the failure types and causes in regenerative braking system were analyzed. The transient behavior characteristics were examined based on fault-diagnosis and fail-safe upon failure of regenerative braking system.

• Journal of the Ergonomics Society of Korea
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• v.28 no.3
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• pp.49-54
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• 2009

Visual occlusion method is a visual demand measuring technique which uses periodic vision/occlusion cycle to simulate driving environment. It became one of the most popular techniques for the evaluation of in-vehicle interfaces due to its robustness and cost-effectiveness. However, it has a limitation in that the vision/occlusion cycle forces the user to use the IVIS at a predetermined pace, while a driver decides when to use the device on his/her own in actual driving. This paper proposes a user-driven visual occlusion method for measuring the visual demand of in-vehicle interfaces. An experiment was conducted to examine the visual demand of an in-vehicle interface prototype using both the existing (system-driven) occlusion method and the proposed (user-driven) one. Two in-vehicle tasks were evaluated: address input and radio tuning. The results showed that, for the radio tuning task, there were significant differences in total shutter open time and resumability ratio between the methods. The user-driven visual occlusion method not only allows a better representation of drivers' behavior, but it also seems to provide more information on the chunkability of a task.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.490-494
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• 2008

U-Channel Bridge is effective bridge type, because its edge beam performs role of barrier and enables to reduce additional dead loads. Although it is effective to reduce additional dead loads, there is possibility of bridge collapse under impact load due to car crash. Also, edge beam must have ability to induce safe driving and prevent falling accidents. Therefore, it requires behavior analysis and property investigation through the vehicle impact crashing edge beam. This study presents method of structural analysis of U-channel bridge and investigates design specifications for the effect of the edge beam under the vehicle impact. Also, it carries out stability investigation of behavior of edge beam and slab, based on Korean Highway Bridge Design Specifications and AASHTO LRFD Bridge Design Specification.

• Journal of the Ergonomics Society of Korea
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• v.29 no.5
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• pp.735-739
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• 2010

Driving workload is increasing according to developing new in-vehicle devices and introducing driving information systems. In this research using a driving simulator, EFRP (Eye Fixation Related Potential) was measured for evaluating driving attention and distraction while tasking cognitive workload, n-back tasks. The result of EFRP was compared with driver behaviors. Results suggest that EFRP is able to use for a method of evaluating driving workload, however, the analysis of driver behavior is difficult to find driving attention and distraction in the case of free flow of traffic situation.

• Journal of Advanced Navigation Technology
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• v.17 no.2
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• pp.165-170
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• 2013

In this paper, we propose the information acquisition and analysis system for a vehicle driver in order to provide the safe driving environments. We first define the list of reckless driving behaviors and propose the recognition system, which recognizes the reckless behaviors, by using the acquired information. The collaboration among the information acquisition, the analysis, and the behavior comparison modules increases the accuracy of the recognition rate. Our system alarms to a vehicle driver in order to notify the potential to confront the dangerous situation due to the abnormal or reckless driving behaviors.