• Nuclear Engineering and Technology
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• 제54권3호
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• pp.1145-1151
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• 2022

A hybrid cutting using both plasma and end mill was developed for safe and efficient dismantling of nuclear facilities. In this cutting method, a moving arc plasma heats up the workpiece before milling. Thermally softened part of the workpiece is then removed quickly and deeply with an end mill. For the cutting experiments, a three-axis numerical control (NC) milling machine was combined with a commercialized arc plasma torch and used to cut 25 mm thick stainless steel plates. Experimental results revealed that pre-heating by arc plasmas can improve the cutting volume per unit time higher than 40% by reducing the cutting load and increasing the cuttable depth when using an end mill without cutting fluids. These advantages of a hybrid cutting process are expected to contribute to quick and safe segmentations of metal structures with radioactively contaminated inner surfaces.

• Journal of Welding and Joining
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• 제9권4호
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• pp.69-74
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• 1991

The Plasma Arc Cutting Method using high density and hight temperature beam is well applicable to the cutting of the nonferrous metal (Al alloy ) and stainless steel which are unable to be cut by the use of the oxy-fuel gas. This study focalizes on the cutting phenomena of the plate of (mm) thickness, since the cutting phenomena of thick plates have been rather thoroughly studied. In this study the cutting groove, adhesive phenomena of dross, surface roughness were measured according to the variation of cutting speed and compared with the case of mild steel plates. The result showed that the kerf width variation of Al alloy was similar to the case of mild steel, while that of the stainless steel differed from the mild steel. In the adhesive phenomena of dross, 6(mm) thick plates of Al alloy showed a difference from those of thick plates, but the stainless steel was similar to thick plates. The surface roughness variation of Al alloy wias minimum at 67 cm/min, while that of stainless steel was at 30cm/min.

• Steel and Composite Structures
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• 제6권6호
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• pp.531-555
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• 2006

H-shaped welded steel column members are fabricated by welding together pre-cut flanges and the web. Modern fabricators are increasingly using plasma-cutting technique instead of traditional flame cutting. Different fabrication techniques result in different degrees of geometric imperfections and residual stresses, which can have considerable influence on the strength of steel columns. This paper presents the experimental investigation based temperature profiles, geometric imperfections, and built-in residual stresses in plasma cut-welded H-shaped steel column members and in similar flame cut-welded H-shaped steel columns. Temperature measurements were taken during and immediately after the cutting operations and the welding operations. The geometric imperfections were established at closely spaced grid locations on the original plates, after cutting plates into plate strips, and after welding plate strips into columns. Geometric imperfections associated with plasma cut element and members were found to be less than those of the corresponding elements and members made by flame cutting. The "Method of Section" technique was used to establish the residual stresses in the plate, plate strip, and in the welded columns. Higher residual stress values were observed in flame cut-welded columns. Models for idealized residual stress distributions for plasma cut and flame cut welded sections have been proposed.

• 한국CDE학회논문집
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• 제9권2호
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• pp.102-111
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• 2004

In this paper, the efficient layout method for generating common and continuous cutting path of flat-bar profile. The ‘flat -bar’ is a stiffener and has long rectangular shape. This paper describes a fast nesting algorithm of the flat-bar, and a procedure to generate cutting path of gas/plasma torch, which is operated by a NC (numerically controlled) gas/plasma cutting machine. By using this common and continuous path, the machining-time for cutting and the maintenance-cost of plasma-torch could be reduced. Proposed procedures are written in C-language and applied to the Interactive Flat-Bar-Nesting System executable on Open VMS with X-Window system.

• 한국기계가공학회지
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• 제14권3호
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• pp.112-123
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• 2015

There are many systems for cutting plates or pipes into a desired shape. A typical system is a plasma cutter. It uses plasma, which means that an effective design of the table supporting the workpiece is an important issue in order to ensure a long operational career. Conventional roller-support worktables have a short lifespan due to scratches from the plasma, and it is also difficult to maintain the roller balance. By using a bolt-fastening method, deformation and failure of the final product can occur due to the stress concentration at bolting points. To escape these issues, a polygon support and bracket fastening method was designed. Due to polygons having a number of support surfaces, when one surface has been damaged, it is possible to reuse the support by utilizing a different surface. The bracket-fastening method can extend the worktable lifetime and increase productivity by reducing stress concentration. In this paper, the polygon support/bracket-fastening method is compared with existing technologies. Consequently, performance benchmarks are verified through a structure analysis and experimentation.

• 한국생산제조학회지
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• 제21권5호
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• pp.755-760
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• 2012

In this study, three dimensional cutting force components and surface roughness appeared in high speed cutting by using tungsten carbide endmill tools implanted ion or not found mutual relations through several analysis of statistical dispersion. It is showed that cutting force(Fx) is affect with spindle speed and feed rate, cutting force(Fy) is affect with spindle speed and ion implantation time and cutting force(Fz) is affect with feed rate in interaction through the statistical method of ANOVA of cutting force and surface roughness, it is analyzed that it is affected of spindle speed and feed rate in surface roughness.

• 한국기계가공학회지
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• 제21권1호
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• pp.22-27
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• 2022

In accordance with the growing trend of decommissioning nuclear facilities, research on the cutting process is actively proceeding worldwide. In general, a thermal cutting process, such as plasma cutting is applied to decommissioning a nuclear reactor pressure vessel (RPV). Plasma cutting has the advantage of removing the radioactive materials and being able to cut thick materials. However, when operating under water, the molten metal remains in the cut plane and re-solidifies. Hence, cutting is not entirely accomplished. For these environmental reasons, it is difficult to cut thick metal. The contact arc metal cutting (CAMC) process can be used to cut thick metal under water. CAMC is a process that cuts metal using a plate-shaped electrode based on a high-current arc plasma heat source. During the cutting process, high-pressure water is sprayed from the electrode to remove the molten metal, known as rinsing. As the CAMC is conducted without using a shielding gas, such as Argon, the electrode is consumed during the process. In this study, CAMC is introduced as a method for dismantling nuclear vessels and the relationship between the metal removal and electrode consumption is investigated according to the cutting conditions.

• Journal of Welding and Joining
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• 제30권4호
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• pp.44-48
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• 2012

H-beam used for stiffening the upper structure of ocean plant is cut in the various shapes. The cutting process of the H-beam is done manually and requires a long time and high cost. Therefore, automation of H-beam cutting is an important task. This research aims to develop a 3-D simulator to build the automatic H-beam cutting system and to determine the optimal cutting method. The automatic H-beam cutting system composes of 6 robots including 2 cutting robots hang to a crane and 1 conveyer. The appropriate system layout for covering the various sizes and types of H-beam was tested and determined using the simulator. The H-beam cutting system uses a hybrid type of plasma and gas cutting because of special cutting shapes of H-beam. The cutting area of each cutting method should be properly divided according to the size and shape of H-beam to shorten the total cutting time. Additionally the collision between a robot and a robot or a robot and H-beam should be avoided. The optimal cutting method for the shortest cutting time without the collision could be found for the various cutting conditions by use of the simulator. 2 simulation samples shows the availability of the simulator to find the optimal cutting method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1404-1406
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• 1995

In this paper, argon gas was used for numerical analysis of an arc in a cutting plasma torch driven by constant current. We established nozzle-constricting type torch domain and calculated steady state characteristics of argon arc plasma using the control volume method(CVM). For simplicity, we assumed that the flow field is laminar and the local thermodynamic equilibrium(LTE) prevails in all domain regions. We also neglected cathode-fall and anode-fall effects. Considering magnetic pinch effect and viscosity effect, we solved the momentum equation. Voltage drop in the arc column due to input current was calculated from the temperature field obtained by the energy balance equation.

• 전력전자학회논문지
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• 제14권1호
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• pp.72-81
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• 2009

본 논문에서는 대기압 플라즈마 발생용 정현파펄스형 교류 전원 장치에 대한 연구를 진행하였다. 정현파펄스형 전원장치는 기존의 LC공진을 이용한 교류 전원장치보다 높은 dv/dt를 갖게 되므로 안정적인 플라즈마 공급이 가능하며 펄스형에 비해 고조파 노이즈가 적고, 정전류 턴온-영전압 턴오프 형태로 동작하므로 매우 높은 효율을 갖는다. 또한 플라즈마 점화 기능을 강화하고 안정적인 전압제어를 위해 3상 부스트형 컨버터를 입력단에 사용하여 입력 역률이 매우 높은 시스템을 구성할 수 있다. 실험실 수준의 10kW부하시설을 사용하여 본 연구의 결과를 입증하였다.