• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.39-47
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• 2005

In this paper, a novel high power micropump using active check valves in place of conventional passive check valves employed at the inlet and outlet ports is presented. It actively controls open/close motion of check valves using piezoelectric actuator for expansion/contraction of pump chamber. A prototype micropump having an effective size of $17mm{\times}8mm{\times}11mm$ is fabricated. Frequency-dependent flow rate characteristics, bi-directional flow characteristics and load characteristics are experimentally investigated using a timing control method for valve closing motion. From the obtained experimental results, it is ascertained that optimal values of the phase shift compared to the voltage to drive pump chamber are $15^{\circ}$ for inlet check valve and $195^{\circ}$ for outlet. Based on the obtained results, a sheet-type active shuttle valve that has a unified valve-body for inlet and outlet check valves is proposed. A micropump with an effective size of $10mm{\times}10mm{\times}10mm$ is fabricated and the basic characteristics are experimentally investigated.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1864-1869
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• 2003

A novel piezoelectric micropump using active check valves in place of conventional passive check valves in inlet and outlet has been proposed and investigated. It actively controls open/close motion of check valves using piezoelectric actuator for expansion/contraction of pump chamber. In this paper, bi-directional flow characteristics and load characteristics are experimentally investigated using an adequate timing control for valve closing motion with a prototype micropump fabricated with the effective size of $17{\times}8{\times}11mm^{3}$. From the experimental results, it is ascertained that optimal values of phase shift against voltage to drive pump chamber for realization of a miniaturized but powerful micropump, are $15^{\circ}$ in inlet check valve and $195^{\circ}$ in outlet. Based on the obtained results, a sheet-type active shuttle valve that has a unified valve-body for inlet and outlet check valves is proposed. A micropump with the effective size of $10{\times}10{\times}10mm^{3}$ is fabricated and basic characteristics are experimentally investigated.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.6
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• pp.22-32
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• 1998

This paper describes a research work of developing a computer-aided design of irregularly shaped-sheet metal product with bending and piercing operation for progressive working. An approach to the CAD system is based on the knowledge-based rules. Knowledge for the CAD system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system has been written in AutoLISP on the AutoCAD with a personal computer and is composed of five main modules, which are input and shape treatment, flat pattern-layout, production feasibility check, blank-layout, and strip-layout module. Based on knowledge-based rules, the system is designed by considering several factors, such as radius and angle of bend, material and thickness of product, complexities of blank geometry and punch profile, and availability of press. This system is capable of unfolding a formed sheet metal part to give flat pattern and automatically account for the adjustment of bend allowances to match tooling requirements by checking dimensions and the best utilization ratio of blank-layout within bending production feasibility area which is beyond ${\pm}30^{\circ}$ degrees intersecting angle between grain flow and bending edge line and which is suitable to progressive bending operation. Also the strip-layout drawing generated by a bending and a piercing operation according to punch profiles divided into automatically for external area of irregularly shaped-sheet metal product is displayed in graphic forms.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1312-1316
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• 2007

Strip casted and rolled magnesium sheet is become exiting material for car manufacturer, due to its better formability and specific strength compare with conventional extruded sheet. TWB technology was attractive for car body designer, because it saves the weight of the car without strength loss. In this study, the laser welding performance of magnesium sheet was investigated for Mg TWB panel manufacturing. The material was strip casted and rolled magnesium alloy sheet contains 3 wt% Al and 1 wt% Zn (AZ31). Lamp pumped Nd:YAG laser of 2kW was used and its laser light was delivered by optical fiber of 0.6mm core diameter to material surface with focusing optics of 200mm focal length for TWB welding. The microstructure of weld bead was investigated to check internal defects such as inclusion, porosity and cracks. Also mechanical properties and formability were evaluated for press forming of car body. For the results, there was no crack but inclusion or porosity on weld at some conditions.The tensile strength of weld was over 95% of base metal. Inner and outer panel of engine hood were press formed and assembled at elevated temperature.

• Bulletin of the Society of Naval Architects of Korea
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• v.8 no.1
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• pp.1-16
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• 1971

Ship hulls obtained by the streamline tracing method usually have characteristically drooped keel lines at the bottom, and a flattening of these bottoms would contribute considerably in utilizing these analytically obtainable hull forms in practical usage. In this dissertation, the author deals with a study on the determination of a practical hull form by the streamline tracing method with a particular emphasis on the bottom flattening problem. Investigations are centered around the form and the terms of bottom doublet distribution. Several examples are computed by varying bottom doublet sheet systematically while the main side source distribution is kept the same. The following conclusions are obtained based on those computed results: after the strength of a bottom doublet sheet can be determined more easily and efficiently by employing the concept of a control plane. If the distance from the distributed plane of the bottom doublet sheet to the control plane is defined as the control distance, the strength of the bottom doublet sheet, the flatness of traced lines, and the increment of the beam length ratio by adding the bottom doublet sheet are all related to the control distance by linear equations near the design bottom. It is observed that a better result can be obtained by using a "line-sampling method" for ${\zeta}_K>2T/L$, and a "plane-sampling method" for ${\zeta}_K{\leq}2T/L$, provided that the check points are sampled in the range ${\xi}{\leq}0.7$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.10a
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• pp.44-54
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• 1994

A variational formulation and the associated finite elemet equations have been derived for general three-dimensional deformation of a planar anisotropic rigid-plastic sheet metal which obeys the strain-rate potential proposed by BARLAT et al [13]. By using the natural convected coordinate system, the effect of geometric change and the rotation of planar anisotropic axes are considered efficiently. In order to check the validity of present formulation, a cylindrical cup and a square cup deep drawing test was modeled. good agreement was found between the FE simulation and the experiment. The results have shown that the present formulation for planar anisotropic deformation can be efficiently applied to the analysis of sheet metal working processes for planar anisotropic nonferrous metals.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.122-128
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• 2004

In order to make a doubly-curved sheet metal effectively, a sheet metal forming process has been developed by adopting the flexibility of the incremental forming process and the principle of bending deformation which causes slight deformation in thickness. The developed process is an unconstrained forming process with no holder. For this study, the experimental equipment is set up with the roll set which consists of two pairs of support rolls and one center roll. In the experiments using aluminum sheets, it is found that the curvature of the formed sheet metal is determined by controlling the distance between supporting rolls in pairs and the forming depth of the center roll and it also depends on the thickness of the sheet metal. In order to check the effect of process parameters on the generation of sheet metal curvatures in this process, the orthogonal array is adopted. From the experimental results, among the process parameters, the distance between supporting rolls in pairs along the direction of one principal radius of curvature as well as the forming depth and the thickness of the material is shown to influence the generation of curvature in the same direction significantly. That is, the other distance between supporting rolls in pairs which are not located in the same direction of one principal radius of curvature, does not have an significant effect on the generation of the curvature in that direction. It mainly affects the generation of curvature in its own direction with the forming depth and the thickness of the material.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.08a
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• pp.53-57
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• 2003

In order to make a doubly curved sheet metal effectively, a sheet metal farming process has been developed by adopting the flexibility of the incremental forming process and the principle of bending deformation which causes slight deformation to thickness. The developed process is an unconstrained forming process with no holder. For this study, the experimental equipment is set up with the roll set which consists of two pairs of support rolls and one center roll. In the experiments using aluminum sheets, it is found that the curvature of the formed sheet metal is determined by controlling the distance between supporting rolls in pairs and the forming depth of the center roll and it also depends on the thickness of the sheet metal. In order to check the effect of process parameters on the generation of sheet metal curvatures in this process, the orthogonal array is adopted. From the experimental results, among the process parameters, the distance between supporting rolls in pairs along the same direction of one principle radius of curvature as well as the forming depth and the thickness of the material is shown to influence the generation of curvature in the same direction significantly. That is, the other distance between supporting rolls in pairs which are not located in the same direction of one principle radius of curvature, does not have an significant effect on the generation of the curvature in that direction. It just affects the generation of curvature in its own direction mainly with the forming depth and the thickness of the material.

• Journal of the Korea Institute of Building Construction
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• v.13 no.1
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• pp.90-100
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• 2013

Deck-plates are widely used on construction sites, and have the advantage of enabling contractors to achieve a relatively uniform quality. But nevertheless, quality deviation in deck-plate construction can occur as the result of differences in site conditions and the experience of crew workers. In this study, the authors present a site quality evaluation prototype for building deck-plate construction. Through analyses of case studies and interviews with experts, standard quality check sheets and a quality management index were developed by estimating the importance of quality check items based on a Failure Mode and Effects Analysis (FMEA) method. The applicability and effectiveness of the prototype was evaluated through a case study and interviews with case participants. It was found that the prototype promoted an active quality management as a way of continuously improving quality management in deck-plate construction instead of passive quality inspection practice.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.8
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• pp.174-182
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• 1998

This paper describes a research work of developing a computer-aided design and machining of irregular shaped-sheet metal product for blanking or piercing operation. An approach to the CAD/CAM system is based on the knowledge-based rules. Knowledge for the CAD/CAM system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system has been written in AutoLISP on the AutoCAD and in customer tool kit on the SmartCAM with a personal computer and is composed of nine modules, which are input and shape treatment, flat pattern-layout, production feasibility check, blank-layout, strip-layout, die-layout, data conversion, modelling, and post-processor module. Based on knowledge-based rules, the system is designed by considering several factors, such as material and thickness of product, complexities of blank geometry and punch profile, diameter and material of a wire, and availability of press. This system is capable of generating NC data automatically according to drawings of die-layout module. Results which are carried out in each module will provide efficiencies to the designer and the manufacturer of blanking or piercing die in this field.