• Journal of the Korean Society for Railway
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• v.13 no.6
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• pp.577-582
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• 2010

The importance of maintenance of rail surface defects is increasing according to the KTX operation. That is because during high speed operation of rolling stocks, rail surface defects shorten fatigue life of rail, accelerate track degradation and deteriorate ride comfort. Rail grinding has been applied for effective rail maintenance in Kyeong-Bu HS line. This paper evaluates the effectiveness of rail grinding in term of rail fatigue life. To this end, the stresses of the rail are measured under KTX running and the equivalent stress range is calculated by RMC after the frequency analysis done with rainflow counting method. Also, The Modified Miner's rule is applied to predict the fatigue life of ground rail. The result of the analysis shows that the fatigue life of ground rail is increased by 15%.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.6
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• pp.284-298
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• 2023

With the rapid advances in automated driving technology, opportunities to experience automated driving directly or indirectly are being provided to the public. On the other hand, research on the preferred automated driving patterns from the user's perspective has not been conducted in Korea. This study used a driving simulator and an experimental vehicle capable of automated driving to evaluate the user satisfaction regarding longitudinal and lateral accelerations. Automated driving patterns were implemented in a virtual environment simulation using five values of longitudinal and lateral accelerations derived from driving experiments. Among these values, three were implemented through experimental vehicle-based automated driving to evaluate satisfaction and anxiety. The participants evaluated lateral acceleration more sensitively than longitudinal acceleration and showed higher levels of anxiety. Based on these results, the necessity of user-oriented evaluation research for automated driving patterns and the suitability of simulator-based evaluation methods were presented.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1421-1426
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• 2012

Cornering maneuvers with reduced body roll and without comfort loss are important requirements for car manufacturers. An electric active roll control(ARC) system controls the body roll angle by using motor-driven actuators installed at the centers of the front and rear stabilizer bars. Co-simulation using the Matlab/Simulink controller model and the CarSim vehicle model was proposed to evaluate the performance of the ARC control algorithm. To validate the performance of the ARC actuator and system, bench tests and vehicle tests were proposed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.189-196
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• 2011

Recently, research and development of a hybrid system for passenger cars as well as for heavy-duty vehicles has become more intensive. An electric powertrain system using an electric motor can replace conventional gasoline and diesel engines. The electric motor has a higher efficiency, better acceleration performance, and is more comfortable than conventional powertrain systems; however, new methods for assessing power performance and energy convergence efficiency have to be investigated because the characteristics of an electric motor are entirely different from those of an internal combustion engine (ICE). In this study, an experiment was carried out on a motor (PMSM: Permanent Magnet Synchronous Motor) test bench. One simple driving mode and four other driving modes identified from real-world driving data of a city bus were selected to perform the experiment on the motor test bench. Then, methods for assessing the acceleration performance, energy convergence efficiency, regenerative effect, etc., were investigated. It was found that the energy efficiency of PMSM was about 90% and that 40% of demand energy was regenerated.

• Journal of the Korea Convergence Society
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• v.10 no.6
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• pp.179-184
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• 2019

Recently, various problems have arisen due to the popularization and aging of urban railway transit, which is the key transportation of large cities. In this study, the vibrational accelerations for the Daegu Metropolitan City Urban Railway(Line 1) were measured and evaluated using the smartphone built-in acceleration sensor and the approved application. For this purpose, the three axes running accelerations were measured according to the domestic standard (KS R 9160), and the acceleration data along the 32 stations (3 directions) were analyzed and compared. In addition, the increasing of acceleration values caused by the change of vibrational environment was monitored along the main stations between the time in 1997 and 2017. It was found that there are considerable increase of lateral and vertical directional accelerations due to the aging of railway facility environment for the last 20 years. The results of this study have valuable means for evaluating the ride quality of urban railway and the vibration influence on surrounding structures.

• Composites Research
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• v.26 no.6
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• pp.386-391
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• 2013

In this paper, a carbon fiber/epoxy composite-aluminum hybrid wheel for passenger cars was suggested for better performance and a prototype was fabricated and tested. Adhesive bonding between aluminum part and a composite rim part was used, and the bonding length and thickness were determined by finite element analysis. For self alignment and the function of bonding jig the special structure with a groove and a protrusion was applied. To evaluate the performance of the hybrid wheel various FE analyses were carried out. Inner and outer molds were prepared for the composite rim part and the thermoformed composite part was bonded to the aluminum part. Vibration tests revealed that the hybrid wheel had 16% higher resonance frequency and 32% higher damping capacity with 10% weight reduction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.86-93
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• 2010

The wear of railway track affects loss of rough ride, noise or vibration of train and traveling safety. Moreover as the track is worn away, this promotes destruction of structural mechanism of rail track which can bring about increasing of rail track maintenance cost drastically. For this reason, it is very important and interested research subject to design railway track structure and to analyse train movement mechanism based on systematic analysis of the reasons causing rail wear possible in real field. In this research, for the efficient maintenance, Life Cycle Performance of rail track and maintenance characteristics are computed considering some track components such as track type, contracting type, sleeper type and roadbed type. Time - Wear probabilistic distribution relationship as well as multiple regression analysis based on time, curvature and wear data are computed to predict the service life remainder of railway track and to be adapted to safety assessment.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.4 s.23
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• pp.1-6
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• 2006

In terms of the speed-up of the conventional line, the research for a improved turnout was carried out continually around world. A turnout is known that it is the most unstable equipment structurally in the rail system. So, the turnout is needed more stable structure. An accurate assembly of turnout affects traveling qualify of turnout area and running safety. Therefore, a turnout which is pre-assembled at a factory by using the split PC sleeper is transported to construction site recently in advanced countries. In this paper, the performance measurements which estimate the safety of the split PC sleepers which are adopted for the first time to improve performance of turnout are implemented indoors. The split PC sleeper is one of components of the improved turnout. The test is considered of the worst ballast condition under the maintenance work as like STT(Swithc Tie Tamper) or MTT(Multiple Tie Tamper). These experiments results indicate that structural safety for the expansion joint of the split PC sleepers.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.65-71
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• 2017

This work presents a comparative work on the ride comfort of a quarter car suspension system between two different magneto-rheological (MR) dampers; one is conventional type without bypass hole and the other is featured by several bypass holes in the piston. As a first step, two different MR dampers are designed on the basis of the governing equation and manufactured with same geometric dimensions except the bypass holes. After investigating the field-dependent damping properties, two dampers are installed to the quarter car suspension system. The suspension model is then derived and a sky-hook controller is implemented to identify vibration control performance under random road. It is shown that the suspension system with MR damper featured by the bypass holes can provide much better ride quality than the case without the bypass holes. This is validated via experimental implementation.

• International Journal of Highway Engineering
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• v.19 no.5
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• pp.97-106
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• 2017

PURPOSES: This study aims to evaluate the effects of vehicle dynamic behaviors on ride quality. METHODS : Simulation and field test were conducted to analyze the behavior of a driving vehicle. The simulation program CarSIM was applied and an INS (Inertial Navigation System) was used for field experiments. A small simulator was developed to simulate vehicle behavior such as roll, pitch, and bounce. The panels evaluated the ride quality in five stages from "very satisfied"to "very dissatisfied."Experiments were conducted on a total of 144 cases of vehicle behavior combinations. RESULTS :In both simulation and field tests, pitch is the largest and yaw the smallest. Especially in the field test, the amount of yaw is very low, about 7% of pitch and 18% of roll. The sensitive and extensive analysis conducted related ride quality with changing the frequency and amplitude. It was found that the most sensitive frequency range is 8 Hz across all amplitudes. Moreover, the combination of the roll and bounce was most sensitive to the ride quality at the low-frequency range. CONCLUSIONS : This result show that the vertical vehicle behavior (bounce) as well as the rotational behavior (roll and pitch) are highly correlated with ride quality. Therefore, it is expected that a more reasonable roughness index can be developed through a combination of vertical and rotational vehicle behavior.