Papers by Author: Sung Il Seo

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Authors: Nam Po Kim, Jung Seok Kim, Sung Il Seo, Tae Won Park
Abstract: This paper shows the experimental study to evaluate the fatigue strength of a bogie frame for Korean tilting train. The various load cases were established based on the international standard (UIC615-4) and the special tilting load case, which is unique in the tilting train, was derived by dynamic analysis and logical assumption of operation under worst tilting condition. The experimental study was conducted by means of two ways, both static and fatigue loading test. Through the static load test, the safety against fatigue was assessed using Goodman diagram of the material used. The fatigue load test was carried out up to 1x107cycles. The fatigue strength was assessed by fatigue crack inspection by means of NDT test at the stage of 6x106cycles and 1x107cycles.
Authors: Choo Soo Park, Sung Il Seo, Sung Hoon Choi, Jin Yong Mok
Abstract: In designing the structures of railway rolling stocks, deterministic methods associated with the concept of a safety factor have been traditionally used. The deterministic approaches based on the mean values of applied loads and material properties have been used as safety verification for the design of the car body structures. The uncertainties in the applied loading for the high speed train and the strength of new materials in the structure require the application of probabilistic approaches to ensure fatigue safety in the desired system. Pressure loadings acting on the car body when the train passes through tunnels show reflected pressure waves for high-speed trains and they may cause a fatigue failure in vehicle bodies. In this paper, it is proposed that a fatigue design and assessment method based on a structural reliability that deals with the loading of pressure variations on a railway vehicle reflected in tunnels and the strength variations of material. Equation for the fatigue reliability index has been formulated to calculate the reliability assessment of a vehicle body under fluctuating pressure loadings in a tunnel. Considered in this formulation are the pressure distribution characteristics, the fatigue strength distribution characteristics, and the concept of stress-transfer functions due to the pressure loading.
Authors: Sung Il Seo, Jung Seok Kim, Se Hyun Cho, Seong Chul Kim
Abstract: Sandwich panels are widely used in the main structure of aircrafts and ships because of their lightweight, high strength, stiffness, durability, and corrosion resistance. The present paper proposes a manufacturing process of a carbody structure of rolling stock using a composite honeycomb sandwich panel. The panel is made of carbon/epoxy composite faces and an aluminum core. The faces bear bending loads and the core shearing load. A product is manufactured by lay-up of composite material on the mold of the product in final dimensions; then cured in a large autoclave for obtaining one body of a structure. In this study, in order to evaluate the mechanical properties of the honeycomb sandwich panel, tensile test, compressive test, flexural test and shear test of the face in honeycomb sandwich panel were performed. Impact test for the honeycomb sandwich panel was also carried out. Moreover, end compression test was conducted. The results show that the composite honeycomb sandwich panel has good properties for the carbody structure of rolling stock.
Authors: Jung Seok Kim, Jong Cheol Jeong, Sang Jin Lee, Se Hyun Cho, Sung Ho Yoon, Seong Ho Han, Sung Il Seo
Abstract: This paper explains the structural safety evaluation of a hybrid composite train carbody. The composite carbody with length of 23m was manufactured as a sandwich structure composed of a 40mm-thick aluminum honeycomb core and 5mm-thick woven fabric CF1263 carbon/epoxy face. In order to evaluate the structural safety of it, the dynamic force of ±0.2g was applied to the full weight carbody by two 50-ton capacity hydraulic actuators. The excitation frequency was determined by the first bending natural frequency evaluation test under full weight condition. The test was conducted for 2x106cycles. During the test, the nondestructive tests using X-ray for the composite body structure and liquid penetrant test for the welding region of the steel underframe were performed.
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