• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2520-2528
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• 2000

Mechanical and physical properties of composite materials make a great difference due to their cure process condition. In order to clarify the effect of cure process condition on the microscopic damage behavior and failure mechanism of Carbon/Epoxy composites, three point bend test has been performed. For this purpose, two kinds of specimens with single adhesive and multiple adhesive layers were prepared. For single adhesive layer, four different types of specimen were used, that is, non-sanding, sanding, cocured, laminated specimens. Three different types of specimen were also used for the multiple adhesive layer, non-sanding, sanding, cocured specimens. Acoustic emission technique has also been employed to monitor the damage progresses associated with each micro-failure mechanism. The characteristics of AE parameters associated with micro-failure mechanism of each specimen were discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.226-229
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• 1999

Epoxy compound has been used as insulation material in electrical equipment for a long time because of its excellent electrical, mechanical and chemical properties. Nowdays, becoming higher voltage system, the properties of interface between epoxy and metal insert become more important. The breakdown voltage of epoxy compound for electric material is variable according to the surface roughness of metal insert. Generally, with metal insert sanding, the adhesion strength is enhanced and the breakdown strength is reduced. But in this study, we knew that the adhesion strength became enhanced but the breakdown strength didn\`t reduced with metal insert sanding. So in this study sanding. So in this study, we suggest the optimum interface condition by adjusting the surface roughness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1524-1530
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• 2003

Translucent plastics are commonly used in packaging of mechanical and/or electrical components. Although Rapid Prototyping(RP) provides prototypes of various materials, translucent RP parts are not readily available from most RP processes. ABSi is one of the ABS materials available for Stratasys' FDM process, and the material had potential to be translucent. In this paper, two post-processing techniques were applied in order to increase optical transmissivity of the parts made of FDM's ABSi. First, elevated temperature condition was applied resulting in increased transmissivity while dimensional shrinkage was observed. Second, resin infiltration and surface sanding provided up tp 16 ％ transmissivity without shrinkage. These post-processes can be selectively applied to increase transmissivity of ABSi parts. Thus, translucent FDM part can be fabricated from regular FDM process followed by the post-processes developed in this study.

• International Journal of Ocean System Engineering
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• v.2 no.3
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• pp.185-194
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• 2012

A Macroscopic combination of two or more distinct materials is commonly referred to as a "Composite Material", having been designed mechanically and chemically superior in function and characteristic than its individual constituent materials. Composite materials are used not only for aerospace and military, but also heavily used in boat/ship building and general composite industries which we are seeing increasingly more. Regardless of the various applications for composite materials, the industry is still limited and requires better fabrication technology and methodology in order to expand and grow. An example of this is that the majority of fabrication facilities nearby still use an antiquated wet lay-up process where fabrication still requires manual hand labor in a 3D environment impeding productivity of composite product design advancement. As an expert in the advanced composites field, I have developed fabrication skills with the use of machinery based on my past composite experience. In autumn 2011, the Korea government confirmed to fund my project. It is the development of a composite sanding machine. I began development of this semi-robotic prototype beginning in 2009. It has possibilities of replacing or augmenting the exhaustive and difficult jobs performed by human hands, such as sanding, grinding, blasting, and polishing in most often, very awkward conditions, and is also will boost productivity, improve surface quality, cut abrasive costs, eliminate vibration injuries, and protect workers from exposure to dust and airborne contamination. Ease of control and operation of the equipment in or outside of the sanding room is a key benefit to end-users. It will prove to be much more economical than normal robotics and minimize errors that commonly occur in factories. The key components and their technologies are a 360 degree rotational shoulder and a wrist that is controlled under PLC controller and joystick manual mode. Development on both of the key modules is complete and are now operational. The Korean government fund boosted my development and I expect to complete full scale development no later than 3rd quarter 2012. Even with the advantages of composite materials, there is still the need to repair or to maintain composite products with a higher level of technology. I have learned many composite repair skills on composite airframe since many composite fabrication skills including repair, requires training for non aerospace applications. The wind energy market is now requiring much larger blades in order to generate more electrical energy for wind farms. One single blade is commonly 50 meters or longer now. When a wind blade becomes damaged from external forces, on-site repair is required on the columns even under strong wind and freezing temperature conditions. In order to correctly obtain polymerization, the repair must be performed on the damaged area within a very limited time. The use of pre-impregnated glass fabric and heating silicone pad and a hot bonder acting precise heating control are surely required.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1193-1198
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• 2003

Translucent plastics are commonly used in packaging of mechanical and/or electrical components. Although Rapid Prototyping(RP) provides prototypes of various materials, translucent RP parts are not readily available from most RP processes. ABSi is one of the ABS materials available for Stratasys' FDM process, and the material has potential to be translucent. In this paper, two post-processing techniques were applied in order to increase optical transmissivity of the parts made of FDM's ABSi. First, elevated temperature condition was applied resulting in increased transmissivity while dimensional shrinkage was observed. Second, resin infiltration and surface sanding provided upto 16% transmissivity without shrinkage. These post-processes can be selectively applied to increase transmissivity of ABSi parts. Thus, translucent FDM part can be fabricated from regular FDM process followed by the post-processes developed in this study.

• Journal of Drive and Control
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• v.14 no.3
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• pp.25-31
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• 2017

This study presents a methodology for simulating a unified approach that controls interaction force between tool and objective by using a synthesis method of robot interacting control law for stabilizing the transient process of motion. Root locus is used to analyze stabilization of motion deviation characteristics. Based on responses of motion deviation, contact force is derived to satisfy exponential stability and we generate control input with respect to motion trajectories and interaction force. Moreover, simulation is applied to experimental application of a Cartesian robot driven by two stepper motors, and the noise of feedback signals is considered as presence of system inaccuracies, and the unified approach of interaction force control is examined precisely.

• Conservation Science in Museum
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• v.27
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• pp.67-90
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• 2022

A C-46 transport aircraft, which can be thought of as a large cultural heritage item from the modern period, was subjected to paint analysis and conservation treatment in preparation for its exhibition. The C-46 is the first aircraft ever dispatched to overseas combat zones by the Korean Air Force and carried out missions during the Vietnam War. The aircraft is mainly made of aluminum and shows signs of corrosion on its surface, including pitting and etching, as well as gray and white powdery attachments. In the analysis of the paint, diatomite(SiO₂·nH₂O) was confirmed in the red paint, titanium dioxide(TiO₂) was identified in the white paint, black iron oxide(Fe₃O₄) was detected in the black paint, and colcothar(Fe₃O₄) mixed with putty was confirmed in the blue paint. Infrared spectroscopy revealed the use of alkyd resin in the paint on the main body and nitrocellulose in the Taegeuk pattern. During the conservation treatment, mechanical cleaning, such as sanding, was conducted to remove paint and varnish from the surface. Corrosion was removed by sanding and cleaning with chemical solvents, and new paints and varnishes were applied. Through the paint analysis and conservation treatment, the aircraft was made available for exhibition in a stable condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1958-1967
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• 2004

This paper describes the method to rapidly fabricate the large-sized physical model with the envelope model size of more than 600 mm${\times}$ 600 mm${\times}$ 600 mm using two type semi-automatic VLM-ST processes in connection with the reverse engineering technology. The fabrication procedure of the large-sized solid shape is as follows: (1) Generation of STL data from 3D scan data using 3D scanner, (2) generation of shell-type STL data by Boolean operation, (3) division of shell-type STL data into several pieces by solid splitting, (4) generation of USL data for each piece with VLM-Slicer, (5) fabrication of each piece by cutting and stacking according to USL data using VLM-ST apparatus, (6) completion of a shell-type prototype by zigzag stacking and assembly for each piece, (7) completion of a 3D solid shape by foam backing, (8) surface finish of a completed 3D solid shape by coating and sanding. In order to examine the applicability of the proposed method, the miniature of the Mount Rushmore Memorial has been fabricated. The envelope model size of the miniature of the Mount Rushmore Memorial is 1,453 mm${\times}$ 760 mm${\times}$ 853 mm in size. From the result of the fabricated miniature of the Mount Rushmore Memorial, it has been shown that the method to fabricate the large object using two type semi-automatic VLM-ST processes in connection with the reverse engineering technology are very fast and efficient.

• Journal of Korea Foundry Society
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• v.31 no.2
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• pp.66-70
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• 2011

Hot dip aluminizing (HDA) is widely used in industry for improving corrosion resistance of material. The formation of intermetallic compound layers during the contact between dissimilar materials at high temperature is common phenomenon. Generally, intermetallic compound layers of $Fe_2Al_5$ and $FeAl_3$ are formed at the Al alloy and Fe substrate interface. In case of cast iron, high contact angle of graphite existed in the matrix inhibits the formation of intermetallic compound layer, which carry with it the disadvantage of a reduced reaction area and mechanical properties. In present work, the process for the removal of graphite existed on the surface of specimen has been investigated. And also HDA was proceeded at $800^{\circ}C$ for 3 minutes in aluminum alloy melt. The efficiency of graphite removal was increased with the reduction of particle size in sanding process. Graphite appears to be present both in the region of melting followed by re-solidification and in the intermetallic compound layer, which could be attributed to the fact that the surface of cast iron is melted down by the formation of low melting point phase with the diffusion of Al and Si to the cast iron. Intermetallic compound layer consisted of $Fe(Al,Si)_3$ and $Fe_2Al_5Si$, the layer formed at cast iron side contained lower amount of Si.