Papers by Author: Sung Cheol Yoon

Abstract: An evaluation was carried out by applying a load to the underframe of the freight car to determine the structural strength of the carbody of a newly manufactured freight car for transportation. This study is aimed at evaluating the safety of the underframe of the freight car under the maximum load conditions. The freight car for use in rail freight was designed mainly with SM490A steel and ASTM A441 steel for production. The carbody for rolling stock is a principal structure supporting major underframe equipment and freight. Thus, strength evaluation of this structure is very important. Both structural analysis and loading test were performed under the loading condition. Prior to evaluating structural strength, finite element method software was used for structural analyses of stress distribution in a carbody of freight car. The strain gages were attached on the carbody based on the FEM results. A vertical load test, compressive load test, measurement of deflection amount and a natural frequency measurement test were conducted.

Abstract: The drive shaft of the bi-modal tram has been designed and built into independent wheel drive; all driving wheels are driven by electric motor-gearbox sets independently, in order to make low floor to provide the old and the handicapped with easy access, and to remove differential gears to reduce turning radius. This paper was aimed to evaluate torques on drive shafts while the bi-modal tram was running on slope way in the test track, and at maximum speed in public roadway. On the basis of the torques measured on the drive shafts, torsion characteristics of the independent wheel drive were discussed in this paper.

Abstract: This study is an experimental research on using stainless steel car body structure for urban railway vehicles. The car body used in the experiment was made of stainless steel. To evaluate the structural characteristics and safety of the stainless car body, static load test was carried out by means of "Performance Test Standard for Electrical Multiple Unit" with the reference code JIS E 7105. The structural safety of the car body was evaluated by implementing vertical load, horizontal compressive load, twist load, and 3-point support tests. Test results verified that the structural safety of a car body was very stable and safe under design load conditions.

Abstract: The truck that is used as running equipment for freight car support is a core structural part that supports the load of the car body and that greatly influences the safety of freights and vehicles, as well as their running performance. The running equipment is composed of truck frames, wheels and wheel axles, independent suspensions, and brakes. Among these components, the truck frame supporting the load of the vehicles and freights may be the most important one. This study was carried out to analyze the structure of truck frames and to determine whether they are safe when the maximum vertical load, breaking load, and front and rear loads are applied to them. This was done by subjecting the truck frames to stress tests and then measuring the stress on each of their parts. Before the load test, a structural-analysis program was used for the stress distribution analysis of the truck frame. To measure the stresses based on the results of the structural analysis, strain gages were attached to the surfaces of truck frames. The results of the stress tests showed that truck frames have a safe vehicle load design.

Abstract: The temperature monitoring on the surface of the railway brake disc was performed using high-speed infrared (IR) camera. The railway brake disc was developed for disc braking of maximum train speed of 180 km/h. The braking tests were conducted with a full scale dynamometer, and a high-speed infrared camera was employed to monitor temperature evolution on the brake disc during braking operation. The high-speed IR camera provides the measurement of temperature change during braking as well as the images of temperature contour on the brake disc surface. In general, the hot spot generation has been considered the main degradation mechanism in railway brake disc. In this investigation, damage evolution due to generation of hot spots on railway brake disc was investigated using the infrared thermography method.

Abstract: The tensile fracture behavior of polymer matrix composite materials was investigated with the aid of a nondestructive evaluation (NDE) technique. The materials, E-glass fiber reinforced epoxy matrix composites, which are applicable to bogie materials in railway vehicles to reduce weight, were used for this investigation. In order to explain stress-strain behavior of polymer matrix composite sample, the infrared thermography technique was employed. A high-speed infrared (IR) camera was used for in-situ monitoring of progressive damages of polymer matrix composite samples during tensile testing. In this investigation, the IR thermography technique was used to facilitate a better understanding of damage evolution, fracture mechanism, and failure mode of polymer matrix composite materials during monotonic loadings.

Abstract: This paper describes the results of structural analysis and loading test of a bogie frame. The purpose of the analysis and test is to evaluate the safety and functionality of the bogie frame under maximum load. The bogie system consist of the bogie frame, suspensions, wheel-sets, a brake system and a transmission system. Of these components, the bogie frame is the major component subjected to the vehicle and passenger loads. The evaluation method used the JIS E 4207 specifications throughout the FEM analysis and static load test. The test results have shown the bogie frame to be safe and stable under design load conditions.

Abstract: This study introduces the structural analysis and the testing results of the composite structure which is applied to tilting train in Korea. The composite structure is made of aluminum honeycomb structure materials like a sandwich. The static load test was performed to evaluate the structural characteristic and stability of the composite structure. Considering the vertical, compressive, torsional load and 3-point supporting type as a testing terms, the structural stability of a carbody was evaluated. Load test are based on "Performance Test Standard for Electrical Multiple Unit" with the reference code JIS E 7105. The test results have been very safety and stable for design load conditions.

Abstract: The electrical units of diesel electric locomotives, which were used for over 30 years, were characterized for deterioration evaluation through insulation resistance measurement, degradation testing, and infrared thermography method. Especially, an infrared camera and thermocouples were employed for the evaluation. The thermocouples were attached on high-voltage cables connected to traction motors, for in-situ measurement of abnormal heating during test running. After test running, the thermographic images were obtained for the inspection of high-voltage cables using the infrared camera. The thermographic results were quantitatively analyzed, and compared with temperature changes during running. In this investigation, various analysis techniques for the safety characterization of diesel electric locomotives have been introduced, and the analysis results have been used to provide the deterioration or wear information in current locomotive systems.

Abstract: The hot spot generation has been considered as the main degradation mechanism in railway brake disc. Therefore, the understanding of hot spots, also called hot judder, which is undesirable low frequency vibrations developed by non-uniform contact area between brake pad material and brake disc, is important for a better understanding of material design as well as enhancement of materials properties in railway brake disc. Also, infrared (IR) thermography is a powerful NDE technique for the characterization of thermal phenomenon in engineering components and/or systems including engineering materials. The high-speed IR camera provides the measurement of temperature change during brake operation as well as the images of temperature contour on the brake disc surface. In this investigation, damage evolution due to generation of hot spots on railway brake disc was investigated using the infrared thermography method. Moreover, based on obtained thermographic images of hot spots, the hot spots and thermal damage of railway brake disc during braking operation were qualitatively analyzed.