• Journal of the Korean Society for Precision Engineering
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• v.7 no.4
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• pp.103-116
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• 1990

The mixed mode surface crack in finite-width plate subjected to uniform shearing has been analyzed in 3-D problem by using boundary element method. The calculations were carried out for the surface crack angles (${\alpha}$) of $0^{\circ}, 15^{\circ}, 30^{\circ}, 45^{\circ}, 60^{\circ}, and 75^{\circ}, $ and for the aspect ratio(a/c) of 0.2, 0.4, 0.6 and 1.0 to get stress intensity factors at the boundary points of the surface crack. For the aspect ratio of 1.0 and the surface crack angles, finite element method was used to check the results in this in this study. Comparison of the results from both method showed good agreement.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.4
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• pp.117-129
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• 1990

The mixed mode surface crack in finite-width plate subjected to uniform shearing has been analyzed in 3-D problem by using boundary element method. The calculations were carried out for the surface crack angles (${\alpha}$) of $0^{\circ}, 15^{\circ}, 30^{\circ}, 45^{\circ}, 60^{\circ}, and 75^{\circ}, $ and for the aspect ratio(a/c) of 0.2, 0.4, 0.6 and 1.0 to get stress intensity factors at the boundary points of the surface crack. For the aspect ratio of 1.0 and the surface crack angles, finite element method was used to check the results in this in this study. Comparison of the results from both method showed good agreement.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.142-150
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• 2002

This study describes a method of finding an optimal path of a soccer robot by using a concentric circle method with different radii of rotation. Comparing with conventional algorithms which try to find the shortest path length, the variable concentric circle method find the shortest moving time. The radius fur the shortest moving time for a given ball location depends on the relative location between a shooting robot and a ball. Practically it is difficult to find an analytical solution due to many unknowns. Assuming a radius of rotation within a possible range, total path moving time can be calculated by adding the times needed for straight path and circular path. Among these times the shortest time is obtained. In this paper, a graphical solution is presented such that the game ground is divided into 3 regions with a minimum, medium, and maximum radius of rotation.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.6
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• pp.108-113
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• 1999

For cylindrical shells, the closed-form solutions are confined to the specific boundary and/or loading conditions. Though the finite element method is certainly a powerful solution approach for the structural dynamics problems, it has been well known to provide the solution reliable only in the low frequency region due to the inherent high sensitivities of structual and numerical modeling errors. Instead, the spectral element method has been proved to provide accurate dynamic characteristics of a structure even at the ultrasonic frequency region. Since the wave characteristic of a cylindrical shell becomes identical to that fo a flat plate as the frequency increases, an equivalent plate model (EPM) representing the high-frequency dynamic characteristics of the cylindrical shell is introduced herein. The EPM-based spectral element analysis solutions are compared with the known analytical solutions for the cylindrical shells to confirm the validity of the present modeling approach.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.112-119
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• 2003

This paper presents the identification of rotor dynamic parameters. The solution of the system equation can be obtained using least square method. The sensitivity analysis is performed to extract optimized solution, which is considered to be insensitive to inherent measurement errors. The cosine and sine term of orbit shapes can be obtain ed through the by experiment of the orbit analysis at a different speed after doing orbit analysis at an arbitrary selected speed. This values measured time domain are used to search the stiffness and damping coefficients of rotor bearing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.501-504
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• 2004

This paper describes the fabrication method for atomic force microscopy(AFM) tip with multi-walled carbon nanotube(MWNT). For making a carbon nanotube (CNT) modified tips, AC electric field which cause the dielectrophoresis was used for alignment and deposition of CNTs in this research. By dropping the MWNT solution and applying an electric field between an AFM tip and an electrode, MWNTs which were dispersed into a diluted solution were directly assembled onto the apex of the AFM tips due to the attraction by the dielectrophoretic force. In this case, we investigate the effect of the angle between a tip axis and an electrode. Experimental setup were presented, and then CNT attached AFM tips are successfully shown in this paper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.739-742
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• 2000

Micro machining technology has been studied to fabricate small size and high accuracy milli-structure products. To perfectly overcome the conventional mechanical machining methods, the chemical mechanical micro machining(C3M) process was developed. The mechanism of C3M process is that chemical solution etches the material and results in the generation of the chemical reacted layer, and the mechanical micro tool subsequently removes the layer. From the fundamental experiments, the C3M process has been founded to have the advantages of lower machining resistance, tool wear, and higher surface quality and form accuracy than conventional methods. This study focuses on the micro grooving of both the metallic material(SKDII, A1) and hard brittle silicon oxide.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.243-248
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• 1992

Computer Integrated Manufacturing(CIM) is a growing technology as a solution for the total automation of a manufacturing system. However, the implementation in the shop floor is extremely difficult due to many reasons. Flexible Manufacturing System (FMS) is usually considered as a solution for the shop floor automation. One of the difficulties in FMS is the communications problem. Since various machinaries with different communications protocols are included, applying a unified scheme is almost impossible. Therefore, a systematic approach is a key point to solve the communication problem. A cell is defined as an automation unit where closely related for a job reside together. A cell is a messenger between upper level computers and lower level machine equipment. In this research, the functions of the cell are defined to have more capabilities than conventional cell since a cell can be often a total manufacturing system in a small to medium sized factory. The cell conducts communications with different machines through the communications schemes established here. A set of software system has been developed according to the defined communications. The software has been tested for a simulation and real experiments for proof.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.354-357
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• 2001

The developed method is proposed to identify rotor dynamic parameters. The method known imbalance vector, which renders over-determined linear system equation. The solution of the system equation can be obtained using least square method. The sensitivity analysis is performed to extract optimized solution, which is considered to be insensitive to inherent measurement errors. As an alternative approach to identify the parameters of bearings and rotor, adding a known imbalance to the rotor produces another equation set to make the system equations over-determined and linearly independent.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1374-1377
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• 2003

Ti-8Ta-3Nb is made for biomaterial. The experimental speciments are as-cast Ti-8Ta-3Nb and Ti-8Ta-3Nb swaged. The solution treatment in the range 760-96$0^{\circ}C$have been carried out. The microstructural investigations have been carried out on the specimens after the solution treatment. and the hardness have been measured. And the specific heat and the dilatometer of Ti-8Ta-3Nb swaged have been measured. From the result, the $\beta$ transus of the alloy was determined to be 880-86$0^{\circ}C$.