• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.1761-1765
• /
• 2008

In the braking of a railroad car, mechanical brake systems using wheel tread and brake disk are applied as well as electrical brake systems by regenerator and rheostat. It is very important to consider the frictional characteristic because kinetic energy of the vehicle is dissipated as converted thermal energy through friction between disk and brake pad during disk braking. A friction coefficient and wear characteristic are decided from the interrelationship of disk and friction material in the disk brake system. Lab-scale dynamometer test on developed brake disk materials for increasing heat resistance was performed in this study. Each candidate material was tested at various braking speeds and pressures and we obtained the friction coefficient and wear characteristic. And we executed comparative evaluation of the result from the test.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.1766-1769
• /
• 2008

INnterior noise characteristic of Korean tilting train(Hanvit 200) under the field test conditions is analyzed in this paper. The test railroad track was selected from Seodaejon to Songjeongri in Honam line. $4^{th}$ and $5^{th}$ car are decided to measure interior noise level among a train of six cars. The test subject open field executed from test sections. The speed of test trains when from existing operation speed and speed up 20% of existing speed. On open field at the time of operation speed of Hanvit 200 trains from below 160km/h interior noise level at $68dBA{\sim}70dBA$.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.11
• /
• pp.617-623
• /
• 2020

Urban railroad vehicles carry many passengers and are the core of an urban railroad transportation system. Therefore, the dynamic performance of the vehicle must be ensured. Dynamic behaviors such as the vibration and ride comfort of railway vehicles are affected by the structure of the suspension system. We analyzed the dynamic behavior of a railway vehicle according to the suspension system of an urban railway vehicle, which is mainly operated in Korea. For two types of vehicles with different suspension structures, the vibration of the vehicles on railway tracks was measured, and dynamic behavior characteristics such as vibration, ride, and vibration reduction rate were analyzed. The result of the test shows that the vibration performance of the body is superior to that of B-bogie in the lateral direction and that of A-bogie in the vertical direction. Overall, the ride quality of the A-bogie car is superior to that of B-bogie. When analyzing the vibration attenuation rate of primary suspension system, the vibration attenuation performance of B-bogie with coil spring was superior to that of A-bogie with a conical rubber spring. The secondary suspension system has better vibration attenuation performance for A-bogie with air springs compared to coil springs.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.10
• /
• pp.547-557
• /
• 2020

In this study, damping control devices were applied to the suspension system of a capsule train, and the effects were investigated to improve the ride comfort. The superconductor electrodynamic suspension (SC-EDS) method is used for the capsule train levitation. This method has advantages such as no gap control and a large gap. However, the SC-EDS method has disadvantages such as large gap variation and small damping characteristics against outer vibration, which causes degradation of the ride comfort. In this study, the damping control devices in the primary and secondary suspension were considered to improve the ride comfort in the capsule train. Damping control devices in the primary and secondary suspension can reduce the vibration transmission from outer disturbances to the bogie and from the bogie to the car body, respectively. Simulations for dynamic characteristics analyses were conducted based on the capsule train dynamic model to investigate the effects of the damping control devices on the ride comfort. As a result, it was confirmed that the ride comfort requirements according to the ISO standard can be satisfied by applying the damping control in the capsule train suspension.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.1
• /
• pp.61-69
• /
• 2020

This study examined the braking characteristics of a heavy haul freight train with P4a distribution valves applied to domestic high-speed freight trains. A freight train was composed of 50 cars, which is twice the normal operation. A braking test was performed to confirm the characteristics of the braking of a heavy haul. The brake cylinder pressures were measured for emergency and service braking on the 1st, 10th, 20th, 30th, and 50th cars. Because the brake signal is transmitted to the pressure through the braking tube connected to the end of the train, the rear vehicle is braking later than the vehicle ahead. Therefore, it is necessary to predict the brake pressures in all cars in a train to supplement the results of the limited tests and calculate the braking distance. The pressure in each car was determined using empirical models of linear interpolation, stepwise, and exponential models, which provided reliable information. The predictive results of the empirical models were compared with the measured results, and the exponential model was predicted relatively accurately. These results are expected to contribute to the safe operation of heavy haul freight trains and can be used to predict the braking distance and calculate the level of impact between vehicles during braking.

• Journal of Korean Society of Transportation
• /
• v.30 no.3
• /
• pp.95-106
• /
• 2012

The railway service in the Seoul metropolitan area is facing variety of l changes such as extension of service coverage, new construction, and introduction of express service which in turn causes changes on demands. The demand affects train operation characteristics (frequency of service, train formation) as well as on the congestion rate which is one of the major evaluation index in metropolitan area user service. For the efficient operation of the train, the relationship among the minimization of fleet number, operating cost, and service level has been analyzed. Using the Powersim, which is a system dynamics (System Dynamics) simulation program for realizing optimized simulation for train-formation, this paper identified that some stations of Gyeong-bu line exceeded limit congestion rate(150%) of a fleet already that means it is best to maintain current condition of the line; however, the Gyeong-in line and the Gwa-chon line showed no excess of the limit congestion rate so that it is possible to reduce 2-4 fleets of train for efficient operation. In addition, in case of Jang-hang line between Cheon-an and Sin-chang, a train consisting of 10 fleets provides services which is same formation of train for Gyeong-bu line. This study proved that the congestion rate will not rise greatly with only 4 fleets of a train for the service in Jang-hang line, and it is considered that a study for shuttle service between Cheon-an and Sin-chang is necessary.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.10
• /
• pp.717-724
• /
• 2017

To improve the running safety of a tram operating on a concrete embedded track, a bogie, the core system of the tram, was developed and fabricated. After it was integrated with the prototype car body, a short distance track with a sharp curve and steep gradient was constructed for the test operation. A formula to check the interference of the wheel flange with the track during running was proposed. Based on the results provided by the formula, the track was designed. Another simple formula was derived to estimate the derailment quotient and the wheel unloading ratio. During running on the track, the acceleration of the car body was measured and the interface status between the wheel and the track was monitored by a video system. According to the results calculated by these simple formulas, the derailment quotient and wheel unloading ratio were estimated to be within the safety criteria. In the actual test, no derailment occurred and the measured acceleration satisfied the criteria. Also, there was no interference between the wheel and track. The video monitoring results showed no signs of derailment, such as the climbing of the wheel. The pinion in the center showed good running safety, contacting smoothly with the rack. The measurements of environmental noise proved that the criteria were satisfied.

• Journal of the Korean Society for Railway
• /
• v.17 no.3
• /
• pp.171-177
• /
• 2014

PWM converter trains exhibit excellent load characteristics in comparison with conventional phase-controlled trains with low power factors, as they can be operated at power factors which are close to unity by means of a voltage vector control method. However, in the case of a high track density or extended feeding, significant line losses and voltage drops can occur. Instead of operating these trains at a fixed unity power factor, this paper suggests a continuous optimal power factor control scheme for each train in an effort to minimize line losses and improve voltage drops according to varying load conditions. The proposed method utilizes the steepest descent algorithm targeting each car in the same feeding section to establish the optimized reactive power compensation levels that can minimize the reactive power loss of the feeder. The results from a simulation of a sample system show that voltage drops can be improved and line losses decreased.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.9
• /
• pp.29-38
• /
• 2015

In this study, track dynamic interaction characteristics caused by the vehicle running through transitional section such as bridge abutments were studied using the finite element analysis program. The geometric condition of track was generated by trigonometric function and allowable maximum track irregularity is determined by KORAIL track maintenance criteria. The sub-infrastructure under rail fastener system was modelled by 3D solid elements. To reduce computational cost only half track line is numerically considered and the roller boundary condition was applied to each side of model. In this study, the vehicle-track dynamic interaction analysis was carried out for standard Korean transition section of concrete track and the dynamic behaviors were investigated. The dynamic characteristics considered are wheel load variation, vertical acceleration at body, and maximum Mises stress at each part of transitional section.

• Tribology and Lubricants
• /
• v.33 no.1
• /
• pp.15-22
• /
• 2017

Because the running speed of vehicles is increasing and a shorter braking distance is required, high heat-resistant brake pads are needed to satisfy the requirements of customers and car makers. In the near future, hazardous materials such as Cu, Cr, Zn, and Sb will be restricted from use in friction materials. Ceramic composites reinforced by carbon fibers are good candidates for eco-friendly friction materials. In this study, we develop ceramic composite friction materials. The friction materials are composed of carbon fibers, Si, SiC, graphite, and phenol resin and are prepared by hot forming and heat treatment at high temperatures. The density, void ratio, and compressive strength are $1.59-1.66g/cm^3$, 16.6-20, and 70-90 MPa, respectively. Friction and wear tests are performed using a pin-on-plate-type reciprocating friction tester at 25, 100, and $200^{\circ}C$. The counterpart material is a CrMoV steel extracted from a KTX brake disc. Friction coefficient, wear amount, and wear mechanism are measured and examined. We determine that the friction coefficients depend on the temperature and the fluctuation of the friction coefficients is larger at higher temperatures. The amount of wear increases with the surface temperatures of the specimens. The tribological properties of the developed composites are similar to those of a Cu-based sintered friction material. Through this study, it is confirmed that ceramic composite materials can be used as friction materials.