Papers by Author: Ji Yeon Shim

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Authors: Reenal Ritesh Chand, Ill Soo Kim, Ji Hye Lee, Jong Pyo Lee, Ji Yeon Shim, Young Su Kim
Abstract: In robotic GMA (Gas Metal Arc) welding process, heat and mass inputs are coupled and transferred by the weld arc and molten base material to the weld pool. The amount and distribution of the input energy are basically controlled by the obvious and careful choices of welding process parameters in order to accomplish the optimal bead geometry and the desired mechanical properties of the quality weldment. To make effective use of automated and robotic GMA welding, it is imperative to predict online faults for bead geometry and welding quality with respect to welding parameters, applicable to all welding positions and covering a wide range of material thickness. To successfully accomplish this objective, two sets of experiment were performed with different welding parameters; the welded samples from SM 490A steel flats adopting the bead-on-plate technique were employed in the experiment. The experimental results of current and voltage waveforms were used to predict the magnitude of bead geometry and welding quality, and to establish the relationships between weld process parameters and online welding faults. MD (Mahalanobis Distance) technique is employed for investigating and modeling of GMA welding process and significance test techniques were applied for the interpretation of the experimental data. Statistical models developed from experimental results which can be used to control the welding process parameters in order to achieve the desired bead geometry based on weld quality criteria.
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Authors: Ji Yeon Shim, Young Choi, Bong Yong Kang
Abstract: The high cost of manufacturing and manufacturing time is required for preliminary experiment by manufacturing various type of coil every time for the forming of the required shape, it is essentially required to develop the coil design technology using a FEM. Thus, in order to form the required shape, it is important to design the coil using a FEM and predict the final forming product. Therefore, in this study developed electro-mechanical coupled FE-model for thin aluminum plate forming using electromagnetic force. In order to carry out this, magnetic pulse forming was carried by electromagnetic forming system total energy of 24kJ. Peck current and discharge speed acquired through magnetic pulse forming experiment using Rogowski current waveform transducer was used as input data in electromagnetic FE-model. Then, calculated electromagnetic force between forming coil and workpiece through the developed electromagnetic model was inputted as a load of mechanical FE-model for the prediction of thin aluminum plate forming shape. As results, developed electromagnetic-mechanical coupled model shall be able to be usefully used when designing the forming coil to secure the required forming shape later.
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Authors: Ji Yeon Shim, Ill Soo Kim, Ji Hye Lee, In Ju Kim, Bong Yong Kang
Abstract: Magnetic pulse forming is based on the principle of generation of a repulsive force called, Lorentz force due to opposing magnetic fields of adjacent conductors. Magnetic pulse forming of light weight materials such as aluminum, magnesium has been studied by many universities, institutes due to its advantages. But magnetic pulse forming is a complicated research area involving different topics in electromagnetic mechanics, plastic working, and materials mechanics. Therefore, development of FE-model of magnetic pulse forming process is a useful approach for better insight into workpiece deformation mechanics with electromagnetic interaction and further provides design and quality control information. To successfully accomplish this objective, a 3-dimensional ax-symmetric electromagnetic numerical model has been developed. The equation was solved using a general mechanics computer program, ANSYS EMAG and LS-DYNA code.
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Authors: Ji Yeon Shim, Ill Soo Kim, Dong Hwan Park, Bong Yong Kang
Abstract: Generally a MPF(Magnetic pulse forming) process refers to the high velocity and high strain rate deformation of a low-ductility materials driven by electromagnetic forces that are generated by the rapid discharge current through the forming coil. The goal of this study was to investigate the main design parameter in MPF. To achieve the above objectives, An intelligent system which consisted of thin 5053 aluminum sheet and bar forming coil was employed for the experiment. The measured strain data have been analyzed using the developed electromagnetic FE-model. The analysis data showed that the uniform electromagnetic force is one of most important design parameters in MPF process.
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