• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.03a
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• pp.159-166
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• 1994

A constitutive model was proposed to analyze creep densification and grain growth of alumina powder compacts during high temperature processing. Theoretical results from the constitutive model were compared with various experimental data of alumina powder compacts in the literature including pressureless sintering, sinter forging and hot pressing. The proposed constitutive equations were implemented into finite element analysis program (ABAQUS) to simulate densification for more complicated geometry and loading conditions. High temperature forming processing of alumina compact with complicated shape was simulated. Processing of Alumina Powder Compacts

• Transactions of Materials Processing
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• v.14 no.9 s.81
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• pp.756-763
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• 2005

The applicability and productivity of hydroforming process can be increased by combining pre- and post-forming processes such as the bending, piercing and embedding process. For the fabrication of automotive parts, the hollow bodies with connecting nuts are widely used to connect parts together. Hollow body with connecting nuts has been conventionally fabricated by welding nuts or screwing in autobody screws. It requires multiple steps and devices fur the welding and/or screwing Therefore in this study, hydro-embedding process that combines the hydraulic embedding of connecting element(nut) with hydroforming process is investigated. Studies on the hydro-embedding technology have been performed to optimize the shape of the connecting element by analyzing the deformed mode of the embedded tube The effects of the shape of the screw tip, screw thread and shape of thread on the connection force between the tube and the connecting element have been investigated to optimize the shape of connecting element. Finite element analysis has also been performed to provide deformation behaviors of the tube surrounding a hole produced by hydro-embedding.

• Transactions of Materials Processing
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• v.13 no.6 s.70
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• pp.484-489
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• 2004

This paper employed a systematic analysis using a 2-D hybrid special finite element containing an edge crack in order to describe the fracture behavior of spot-welds in automotive structures. The 2-D hybrid special finite element is derived form a mixed formulation with a complex potential function with the description of the singularity of a stress field. The hybrid special finite element containing an edge crack can give a better description of its singularity with only one hybrid element surrounding one crack. The advantage of this special element is that it can greatly simplify the numerical modeling of the spot welds. Some numerical examples demonstrate the validity and versatility of the present analysis method. The lap-shear, lap-tension and angle-clip specimens are analyzed and some useful fracture parameters such as the stress intensity factor and the initial direction of crack growth are obtained simultaneously.

• Journal of Information Processing Systems
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• v.15 no.4
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• pp.967-985
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• 2019

Bug report processing is a key element of bug fixing in modern software maintenance. Bug reports are not processed immediately after submission and involve several processes such as bug report deduplication and bug report triage before bug fixing is initiated; however, this method of bug fixing is very inefficient because all these processes are performed manually. Software engineers have persistently highlighted the need to automate these processes, and as a result, many automation techniques have been proposed for bug report processing; however, the accuracy of the existing methods is not satisfactory. Therefore, this study focuses on surveying to improve the accuracy of existing techniques for bug report processing. Reviews of each method proposed in this study consist of a description, used techniques, experiments, and comparison results. The results of this study indicate that research in the field of bug deduplication still lacks and therefore requires numerous studies that integrate clustering and natural language processing. This study further indicates that although all studies in the field of triage are based on machine learning, results of studies on deep learning are still insufficient.

• The KIPS Transactions:PartA
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• v.12A no.6 s.96
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• pp.531-538
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• 2005

In the high performance Analog Information Processing Systems(AIPS), gain boosting or additional gain stage is required when the gain is not sufficient with one stage amplification. This work shows that high gain is neatly obtained by enhancing the gain using the negative resistance element. Compared to the conventional techniques, the proposed scheme enjoys full output swing, small circuit area and power consumption, and the applications to various configurations of amplifiers. The negative resistance element is placed between the differential output nodes when used in the Op-Amp. The HSPICE simulation indicates that enhancement of more than 40 dB is readily obtained in this simple configuration when the negative resistance element is implemented in the form of cross-coupled CMOS inverters.

• Transactions of Materials Processing
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• v.23 no.2
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• pp.95-102
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• 2014

The under-drive brake piston is an important component in automotive transmissions. It changes the velocity by controlling the gear ratio. It has been traditionally manufactured by hot forging. Recently, there has been an effort to replace this traditional manufacturing method with cold forging in order to improve the dimensional accuracy and decrease the surface roughness. Cold forging uses a smaller amount of initial material and also has a shorter cycle time since the forged surface can be the final surface without the need of post-processing such as machining or grinding. In the current study, finite element analysis was conducted to evaluate a process design using an initial plate with reduced thickness. This smaller thickness decreases the amount of material needed for the part as well as the machining to produce the final product.

• Computational Structural Engineering
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• v.8 no.1
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• pp.161-172
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• 1995

An Integrated processing system for finite element structural analysis has been studied. It is designed to control integratedly the preprocessing, the execution and the postprocessing of a finite element structural analysis program on Windows. It becomes a better graphic user interface(GUI) for the concurrent representation of various inputs and outputs through the dialog-type on multi-windows by the multi-tasking and the object linking and embedding(OLE). Data input can be done easily through menus, dialog boxes and automatic stepwise inputs on the multiple windows, and then output results can be seen with input data on the same screen. Efficiency and validity of the system were examined by solving several numerical examples.

• Computational Structural Engineering
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• v.2 no.4
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• pp.69-77
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• 1989

Until recently post-processing of finite element model has been heavily relied on expensive graphic peripheral devices. With the aid of inexpensive microcomputers, very economical post-processor graphics program called MICRO-POST has been developed. Model geometry or results of analysis for the unlimited meshes can be easily presented in a number of low-cost graphic devices. The paper presents the procedure obtaining the device-independent graphics, and the structure and functions of the program. It also describes efficient I/O scheme to overcome the memory limitation, and dialogue-type input technique to control the plot operation in an interactive manner. Through the post processing examples for the general purpose finite element programs, it demonstrates the usefulness of the program.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.5
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• pp.553-559
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• 2019

Various types of nozzles have been used to cope with fire in ships. However, in Korea, precise nozzles that perform fine spraying function are required for fire fighting in case of fire in a ship, and most of these nozzles depend on imports. Therefore, in this study, we developed various types of nozzles to develop the water spray nozzle for evolving fire in the engine room of the ship, and developed an optimal nozzle through flow analysis and fire test. For this purpose, we selected the materials that can satisfy the characteristics of existing nozzle materials and developed the design technology and processing technology in the nozzle considering fluid flow to achieve optimal water spraying performance. In order to develop an optimal nozzle, the flow through the finite element analysis was first analyzed and the nozzle was manufactured. As a result of flow analysis of the developed nozzle, the maximum velocity at the outlets of four holes at 0.3 MPa was about 3m/s and about 0.15 MPa. In addition, when the pressure at the inlet was 1.8 MPa, it showed the outlet speed of about 18m/s and a pressure of 1.2 MPa.

• Transactions of Materials Processing
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• v.32 no.5
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• pp.287-293
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• 2023

This study aims to develop a computational framework based on the finite element method for modeling the hydrogen embrittlement in martensitic steel. The hydrogen embrittlement is a well-known phenomenon, in which the hydrogen penetrates into the surface, flows through the microstructure and finally leads to pre-mature fracture under external or internal stresses. The current numerical model takes into account the effect of hydrogen on the plasticity and failure behavior of martensitic steel under various stress states. This allows for the construction of a failure criterion that accounts for conventional stress states and hydrogen concentration. The developed model is capable of simulating hydrogen diffusion through the lattice based on the distribution of hydrostatic stress. Additionally, it can calculate the hydrogen concentration in trapped sites, such as dislocations, using a local equilibrium assumption, often referred to as Oriani's equilibrium. The developed model parameters are identified through the tensile tests with and without hydrogen environment, and the performance of model can be validated by analyzing fractured automotive part in the hydrogen environment.