• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.11
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• pp.45-54
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• 2018

The primary objective of this study is to develop a conceptual design of all-in-one attachment based steel pipe pile cutting robot that improves the conventional work in safety, quality, convenience and productivity. For this, the following research works are conducted sequentially; 1)literature review, 2)field investigation, 3)selection of element technology for conceptual design, 4)deduction of conceptual design and its work process, 5)technical feasibility analysis of the conceptual design and its work process. As a result, leveling laser and laser detector, plasma cutter, rotary grapple are selected as core technologies. Futhermore, a conceptual design and work process of an all-in-one attachment based steel pipe pile cutting robot are developed based on the core technologies. According to the technical feasibility analysis result, at least 76.8% of the respondents are selected positive answer about each device of the all-in-one attachment based steel pipe cutting robot. It is expected that the application range and impact on the construction industry will be enormous due to the increasing trend of the steel pipe pile market.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.5919-5924
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• 2014

Accumulated dross adhered to the cutting support degrades the cutting accuracy and aggravates the working environment by reducing the efficiency of the dust collector. Furthermore, the cutting machine and product can be damaged by the scattering of molten metal. In this study, an attempt was made to increase the productivity of steel cutting process and improve the working environment by dross control. The dross adhesion characteristics were invested by a cutting experiment and the design concept for a dross removal machine was devised. Finally, a cutting support cleaning system and its operating algorithm were developed. The applicability of the developed system was examined and verified by a long-term field test after installation of the plasma arc cutting system of a shipyard.

• Korean Journal of Materials Research
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• v.31 no.7
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• pp.392-396
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• 2021

Expensive PCBN or ceramic cutting tools are used for processing of difficult-to-cut materials such as Ti and Ni alloy materials. These tools have the problem of breaking easily due to their high hardness but low fracture toughness. To solve these problems, cutting tools that form various coating layers are used in low-cost WC-Co hard material tools, and research on various tool materials is being conducted. In this study, binderless-WC, WC-6 wt%Co, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are densified using horizontal ball milled WC-Co, WC-Co-Mo₂C powders, and spark plasma sintering process (SPS process). Each SPSed Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are almost completely dense, with relative density of up to 99.5 % after the simultaneous application of pressure of 60 MPa and almost no significant change in grain size. The average grain sizes of WC for Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are about 0.37, 0.6, 0.54, and 0.43 ㎛, respectively. Mechanical properties, microstructure, and phase analysis of SPSed Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are investigated.

• Applied Science and Convergence Technology
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• v.26 no.2
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• pp.34-41
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• 2017

A 2.45 GHz microwave plasma with linear antenna has been prepared for hydrophobic and wear-resistible surface coating of carbon steel. Wear-resistible properties are required for the surface protection of cutting tools and achieved by depositing a hydrogenated amorphous carbon film on steel surface through linear microwave plasma source that has $TE_{10}-TEM$ waveguide. Compared to the existing RF plasma source driven by 13.56 MHz, linear microwave plasma source can easily generate high density plasma and provide faster deposition rate and wider process windows. In this study, $Ar/CH_4$ gas mixtures are used for hydrogenated amorphous carbon film deposition. When microwave power of 1000 W is applied, 40 cm long uniform $Ar/CH_4$ plasma could be obtained in gas pressure of 200~400 mTorr. The Vickers hardness measurement of hydrogenated amorphous carbon film on steel surface was evaluated. It was found the optimized deposition condition at $Ar:CH_4=25:25$ sccm, 300 mTorr with microwave power of 1000W and RF bias power of 100W. By deposition of hydrogenated amorphous carbon film, contact angle on steel surfaces increases from $43.9^{\circ}$ to $93.2^{\circ}$.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.66-70
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• 2000

In order to cope with environmental problems caused by harmful gases emitted from various industrial sources, a new technology which employs discharge plasma formed in ordinary atmospheric pressure has been intensively investigated in many industrialized nations. Although a plenty of useful outcomes and suggestions have been made public by scientists in this field, few commercial products which effectively decompose pollutant gases have appeared as yet. This is partly because that the energy efficiency of a most effective plasma reactor has not reached a satisfactory level in comparison with those of devices using conventional technologies. In an attempt to solve the problem mentioned above, we noticed to combine heterogeneous electrical discharges. This concepts is based on that each plasma reactor has its specific spatial region in which chemical reaction are active and by electrically affected with another reactor of different type, the activated region would increase - which may lead to cutting down the energy consumption. To prove this concept experimentally, two different discharge equipments, a plane ceramic-based surface discharge electrode and a corona electrode with tungsten needle may, are selected and combined to fabricate a hybrid plasma reactor. The results are summarized as follows; (1) Ozone concentration generated in the plasma region drastically increases when the positive corona discharge is added to the surface discharge. The rate of increase of ozone depends on the frequency of the surface discharge. The negative corona, however, does not contribute to the improvement of the ozone generation. (2) NO(nitrogen monoxide) decomposition rate also improves by simultaneously applying the surface and the positive corona discharges. The effect of the corona superposition is more evident when the level of the surface discharge is moderate. (3) By adjusting the corona level, the net energy efficiency during NO decomposition improves in comparison with the simple surface discharge reactor.

• Journal of Powder Materials
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• v.14 no.6
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• pp.348-353
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• 2007

In the present study, Zr-base metallic glass (MG) and Zr-base BMG/diamond composites were fabricated using a combination of gas atomization and spark plasma sintering (SPS). The microstructure, thermal stability and mechanical property of both the specimens as atomized and sintered were investigated. The experimental results showed that the SPSed specimens could be densified into nearly 100% and maintained the initial thermal stability at the sintering temperature of 630K. In addition, MG/diamond powder composites were successfully synthesised using SPS process. The composites, even a very low diamond volume fraction, generated a significant increase in compressive strength. With increasing the diamond volume fraction, the compressive strength was also increased due to the addition of hardest diamonds. It suggests that these composites would be potential candidates for a new cutting tool material.

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.44-50
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• 2022

Transition metal carbides (TMCs) are used to process difficult-to-cut materials due to the trend of requiring superior wear and corrosion properties compared to those of cemented carbides used in the cutting industry. In this study, TMC (TiC, TaC, Mo₂C, and NbC)-based cermets were consolidated by spark plasma sintering at 1,300 ℃ (60 ℃min) with a pressure of 60 MPa with Co addition. The sintering behavior of TMCs depended exponentially on the function of the sintering exponent. The Mo₂C-6Co cermet was fully densified, with a relative density of 100.0 %. The Co-binder penetrated the hard phase (carbides) by dissolving and re-precipitating, which completely densified the material. The mechanical properties of the TMCs were determined according to their grain size and elastic modulus: TiC-6Co showed the highest hardness of 1,872.9 MPa, while NbC-6Co showed the highest fracture toughness of 10.6 MPa^*m^1/2. The strengthened grain boundaries due to high interfacial energy could cause a high elastic modules; therefore, TiC-6Co showed a value of 452 ± 12 GPa.

• Journal of Powder Materials
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• v.26 no.2
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• pp.132-137
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• 2019

Tungsten carbide (WC) hard materials are used in various industries and possess a superior hardness compared to other hard materials. They have particularly high melting points, high strength, and abrasion resistance. Accordingly, tungsten carbide hard materials are used for wear-resistant tools, cutting tools, machining tools, and other tooling materials. In this study, the WC-5wt.%Co, Fe, Ni hard materials are densified using the horizontal ball milled WC-Co, WC-Fe, and WC-Ni powders by a spark plasma sintering process. The WC-5Co, WC-5Fe, and WC-5Ni hard materials are almost completely densified with a relative density of up to 99.6% after simultaneous application of a pressure of 60 MPa and an electric current for about 15 min without any significant change in the grain size. The average grain size of WC-5Co, WC-5Fe, and WC-5Ni that was produced through SPS was about 0.421, 0.779, and $0.429{\mu}m$, respectively. The hardness and fracture toughness of the dense WC-5Co, WC-5Fe, WC-5Ni hard materials were also investigated.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.2
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• pp.75-80
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• 2021

The crystal grains of polycrystalline diamond vary depending on deposition conditions and growth thickness. The diamond thin film deposited by the CVD method has a very rough growth surface. On average, the surface roughness of a diamond thin film deposited by CVD is in the range of 1-100 um. However, the high surface roughness of diamond is unsuitable for application in industrial applications, so the surface roughness must be lowered. As the surface roughness decreases, the scattering of incident light is reduced, the heat conduction is improved, the mechanical surface friction coefficient can be lowered, and the transmittance can also be improved. In addition, diamond-coated cutting tools have the advantage of enabling ultra-precise machining. In this study, the surface roughness of diamond was improved by thermal diffusion reaction between diamond carbon atoms and ferrous metals at high temperature for diamond thin films deposited by MPCVD.

• Korean Journal of Construction Engineering and Management
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• v.19 no.6
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• pp.115-123
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• 2018

The primary objective of this study is to develop an all-in-one based steel pipe pile cutting robot prototype that improves the conventional steel pipe pile head cutting work in safety, quality, and productivity. For this, the following research works are conducted sequentially; 1)literature review and expert survey, 2)selection of core technology using AHP analysis, 3)deduction of detail design, 4)verification of structural stability, 5)development of full-scale prototype. As a result leveling laser and laser detector(94.46), plasma cutter(96.72), rotary grapple(98.45) are selected as a core technologies. As an outcome, it is analyzed that gripper, cylinder pivot bracket and gripper base are structurally stable. Their maximum stresses are shown as 43.0%, 19.4%, 5.3% compared to their yield strength respectively. The development of full-scale prototype in this study will be utilized for the development of the all-in-one attachment based steel pipe pile cutting robot commercialization model.