Papers by Author: Young Shin Lee

Abstract: The Korea Atomic Energy Research Institutes has been developing the SMART (System integrated Modular Advanced ReacTor), an environment-friendly nuclear reactor, for the generation of electricity, and to perform desalination. SMART reactors can be exposed to various external and internal loads caused by seismic and coolant flows. Reactor structures need to be maintained for the reactor’s safety and integrity against these loads during the operational time of the SMART. This paper presents two FE-models, 3-D solid models of the reactor internals in the air and in the coolant, and then compares the results of the dynamic characteristic for the two FE-models using a commercial Finite Element tool, ANSYS V12. A solver was selected by the Block Lanczos method. These FE-models are looking forward to being executed in various researches concerning the SMART in further studies.

Abstract: A sandwich construction is applied to wing skins and fuselages, along with many other structures in aeronautical applications, due to its increased stiffness and reduced weight. In this paper, a face-sheet composed of plain-woven composite laminate that uses prepregs (HPW193/RS3232) and a core material of aluminum honeycomb (Al5052/F40-0.0025) is used. Launch vehicle structures have cut-out areas to check the status of the payload and electric equipment. Cut-out areas reduce the structural stiffness of the launch vehicle structure. Changes in the shape of cut-outs can cause a difference in load support ability of the structure. Compression tests and FEM analysis were performed on composite sandwich panels with various types of cut-out, but with the same overall area.

Abstract: Radioactive waste is shipped in casks designed to prevent the release of the radioactive material into the environment in normal accidental conditions. So, the cask must maintain its integrity such as shielding characteristics and leak tightness after the 9m free drop. In this paper, we consider several types of radioactive material transport casks. The drop scenarios for the integrity evaluation are 6 drop cases. The dynamic analysis is performed by applying the various free drop angle of cask for research the dynamic impact behavior and integrity evaluation of a radioactive material transport cask. As a results of impact drop analysis on radioactive material transport cask, the container maintain structural integrity evaluation in 9 meter free drop conditions.

Abstract: The end coupling is the main component of the aluminum hot rolling process. The end coupling used for transmission of rotational power with heavy-duty load. Fracture of the end coupling causes serious economic injury because an end coupling is a very expensive component and takes a long time to repair. To prevent the destruction of the end coupling it is essential for mechanical life cycle to be known. In this paper, a parameter study on end coupling was performed in order to minimize maximum stress of an end coupling under static loads. To verify the interference of spindle assembly with modified end coupling, kinematic simulation was performed by applying the various combination type and dynamic boundary condition of the spindle assembly. The interference of an optimized model did not occur during combination process and driving process. As a result of an optimum design for life extension on end coupling, the maximum stress of end coupling was reduced about 26% compared with original model.

Abstract: This paper reports on experimental and finite element analysis of the free vibration analysis of three rectangular plates under thermal load. The materials of the three rectangular plates were steel, aluminum and stainless-steel, respectively. The dimension of the plate was 0.1 x 0.1 x 0.002 m. Halogen lamps were used for thermal loading. A PCS (Power Control System) electric control system and a scanning vibrometer (Poly Tech) for frequency response function’s (FRF’s) acquisition were used. The applied temperature conditions were from room temperature to 300oC in 50oC steps. The boundary condition was a free-free condition using bungee cord and one entire side of the plate was heated. ABAQUS was used for FEM analysis. At first, the heat transfer analysis was conducted for each temperature condition and the modal analysis afterwards. The FEM model was verified by comparing experiment and FEM analysis. The FEM model for the modal analysis of thermally loaded plates could be verified.

Abstract: On the human-rifle system, the human body is affected by the firing impact. The firing impact will reduce the firing accuracy and change the initial shooting posture. Therefore the study of biomechanical characteristics using human-rifle modeling and numerical investigation is needed. The muscle-skeleton model was developed by the finite element method using beam and spar elements. In this study, a structural analysis has been performed in order to investigate the human body impact by firing a 5.56mm small caliber machine gun. The firing experiments with a standing shooting posture were performed to verify analytical results. The result of this study shows analytical displacements of the human-rifle system and experimental displacements of real firing. In the results, the analytical displacement on the human body is presented.

Abstract: During fuel irradiation tests of material and fuel rods, all parts of cylindrical shells with multiple holes act as heat sources due to fission heat and γ-flux. The thermal stress is induced by a temperature difference among the heat sources. In this study, the thermal stress of the cylindrical structure is minimized by using an optimization method about the geometric variables. The circular shapes of the multi-specimens are investigated. For the thermal analysis of the structure, the finite element method code, ANSYS 8.1 is used. A sub-problem approximation method is used for the structural design optimization.

Abstract: This study contains several estimation methods of the static buckling load for the spacer grid of nuclear fuel assembly in pressurized water reactor. Three different estimation methods were proposed for the calculation of the static buckling loads of spacer grid. The linear and non-linear static buckling analyses were performed to estimate the static buckling load of the spacer grids using ANSYS program. The analyses results were compared with the static buckling test results. Based on the analysis and test results, the applicability of the proposed estimation method for the static buckling load of the spacer grid was investigated.

Abstract: With the increasing needs of the more convenient transportation, wheelchairs are often used by people with mobility disabilities and the elderly people. However, as wheelchairs are primarily designed for the mobility assistive devices, not for the vehicle seats, wheelchair users are exposed to risk factors for neck and upper body injury caused by automobile accidents. In this paper, in accordance with the ANSI/RESNA WC-19, a fixed vehicle mounted wheelchair occupant restraint system (FWORS), wheelchair integrated restraint system (WIRS), and wheelchair integrated x-bend restraint system (WIXRS) are evaluated using computer simulations for the case when a wheelchair is subjected to the frontal impact (20 g, 48 km/h).

Abstract: The foot plays an important role in supporting the body and keeping body balance. An abnormal walking habit breaks the balance of the human body as well as the function of the foot. The foot orthotics which is designed to consider biomechanics effectively distributes the load of the human body on the sole of the foot. In this paper, gait analysis is performed for subjects wearing the orthotics. In this study, three male subjects were selected. The experimental apparatus consists of a plantar pressure analysis system and digital EMG system. The gait characteristics are simulated by ADAMS/LifeMOD. The COP (Center of Pressure), EMG and ground reaction force were investigated. As a result of gait analysis, the path of COP was improved and muscle activities were decreased with orthotics on the abnormal walking subjects.