• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1641-1646
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• 2011

The second-generation magnetic abrasive polishing is one of the nontraditional machining technologies newly developed. Because of the flexibility effect in magnetic abrasive polishing, the precise and mirror like surface can be obtained during this process. In this study, magnetic abrasive polishing process was applied in small grooved surface. As a result, it was seen that the flexible magnetic abrasive tool was effective to remove burrs on the edge of the groove. However, the efficiency of magnetic abrasive polishing at the slot was very low according to increasing depth and width of slot. So, correlation between geometric parameters, such as the depth and width, and surface roughness was evaluated and the minimum width for suitable polishing was found by experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.313-318
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• 2013

Magnetic abrasive polishing is an advanced deburring process for nonmagnetic materials and micropattern products that have non-machinability characteristics. Despite these advantages, there are some problems with using MAP for deburring. MAP has introduced geometric errors into microgrooves because of an over-cutting force caused by uncontrolled magnetic abrasives in the MAP tool. Thus, in this study, to solve this problem, an EP (electrolyte polishing)-MAP hybrid polishing process was developed for deburring microgrooves in an STS316 material. In addition, an evaluation of EP-MAP for the deburring of microgrooves was carried out by profiling the burrs. The results of the experiment showed geometric errors after the deburring process using MAP. However, in the case of EP-MAP, no geometric error was observed after the process because of the lower material removal rate in EP-MAP.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.197-205
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• 1999

소형 히트파이프에서 ？을 구리망사 또는 그루브를 적용할 수 있고 그루브 형상은 U, V 등 다양하다. 망사？은 모세압이 큰 잇점이 있어나 제작 단가가 높다. 그루브？은 대량생산이 용이하나 전밀 가공 기술이 요구된다. 현재까지 국내에서는 노트북 PC의 CPU 냉각에 사용한 소형 히트파이프의 전량을 해외에서 구매하고 있다. 본 연구에서는 직경 7 mm U형 그루브 관을 인발하여 관직경을 축소한 결과 내경 3.6 mm의 외경 4mm 의 V형 그루브관을 얻을 수 있었다. 이 관을 이용하여 소형 히트파이프를 제작하고 열전달 성능 시험을 수행하였다. 열전달 한계는 40~6$0^{\circ}C$ 범위작동온도 경사각 0$^{\circ}$ 에서 3 W를 얻을 수 있었다. U형 그루브 히트파이프에 비하여 모세압 저하로 인하여 낮은 값을 나타내었다. 열저항을 약 0.7~l.3 $^{\circ}C$/W 로 U형 그루브와 유사하였다.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.7-7
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• 2009

TIG 용접에서는 후판 용접의 경우 용입의 한계 때문에 깊고 넓은 그루브 가공을 하여 다층 용접을 한다. 이 때, 그루브를 채우는 용착금속에 의한 응고 수축과 과대한 입열로 인한 변형이 문제시 되고 있다. 변형을 줄이기 위해서는 용착금속의 양과 입열량을 줄여야 한다. 이러한 문제를 해결하기 위해 그루브의 루트패이스를 두껍게 하고 그루브각을 줄여서 용착량을 줄인다. 이때, 좁은 그루브에서 두꺼운 루트패이스를 완전 용입할 수 있는 용접 프로세스가 필요하다. 비드가 좁고 깊은 용입 특성을 가지는 Plasma welding(PAW) 경우에는 좁은 그루브 속에 토치가 접근하기 어려워 적용하기 어렵다. 따라서 접근성이 용이한 TIG 용접에서 높은 용입형상비를 가지는 용접공정 개발이 필요하다. 선행연구로 높은 용입 형상비를 가지는 Active flux Tungsten Inert Gas(ATIG) 용접이 연구되었다. ATIG의 용입 증가 메커니즘으로는 Marangoni effect, 음이온들로 인한 아크 수축 효과, 절연 플럭스에 의한 아크 수축효과 등으로 알려져 있다. 또한 선행연구에서 ATIG에서 Ar가스에 He 또는 $H_2$ 가스를 첨가하면 용입이 더욱 증가하는 것을 확인하였다. 본 연구에서는 A-TIG에 He 가스를 적용하고 아크길이 0.5mm, 1.0mm, 2.0mm와 전극 선단각 30도, 60도, 90도에 따른 용입 형상비와 변형량을 검토하기 위해 실험을 하였다. 실험 결과는 아크길이가 감소할수록 전극 선단각이 증가할수록 용입 형상비는 증가하였고, 변형량은 감소하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4052-4056
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• 2014

These days, household condensing gas boilers are an obligatory trend. The use of environmentally-friendly boilers that emit less pollutant, such as CO and NOx, are strongly recommended. In this paper, heat flow analysis of the additional inner groove in the tube of the secondary latent heat exchanger was studied to increase the efficiency. A 20% difference in the heat transfer area was obtained with the addition of an inner grove, which showed an increase in the amount of heat transferred. This was confirmed using three-dimensional numerical analysis. With the addition of an inner groove, the exit temperature increased by $1^{\circ}C$. This increase in exit temperature was considered to be a substantial increase in the efficiency of the condensing gas boiler.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1379-1386
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• 2013

The present work reports the mismatch limit loads for a V-groove welded pipe for a circumferential crack using finite element (FE) analyses. To integrate the effect of groove angles on mismatch limit loads, one geometry-related slenderness parameter was modified by relevant geometric parameters including the groove angle, crack depth, and root opening based on plastic deformation patterns in the theory of plasticity. Circumferential through-wall cracks are located at the centre of the weldments with two different groove angles ($45^{\circ}$, $90^{\circ}$). With regard to the loading conditions, axial (longitudinal) tension and bending are applied for all cases. For the parent and weld metal, elastic-perfectly plastic materials are considered to simulate and analyze under- and over-matching conditions in plasticity. The overall results from the proposed solutions are found to be similar to the FE results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.19-24
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• 2009

Structural Dynamics Modification (SDM) is a very effective technique to improve structure's dynamic characteristics by adding or removing auxiliary structures, changing material properties and shape of structure. Among those of SDM technique, the method to change shape of structure has been mostly relied on engineer's experience and trial-and-error process which are very time consuming. In order to develop a systematic method to change structure shape, surface grooving technique is studied and successfully applied to HDD cover model. To verify Surface Grooving Technique, fully embossed HDD cover model was optimized. And comparing with previous optimization result, the effectiveness of this surface grooving technique was checked. The shape of groove and 1 st natural frequency were converged to the same result of previous optimization.

• Journal of the Korean Institute of Gas
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• v.10 no.2 s.31
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• pp.40-46
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• 2006

In this paper, the optimized design of a rectangular O-ring groove has been analyzed for a maximum Cauchy stress and maximum strain using the Taguchi method. This method may efficiently optimize the design parameters for an O-ring groove of a LPG filling unit. The computed FEM results indicate that the optimized design parameters can only be drawn by nine experimental numbers of iterations when the Taguchi design technique has been employed with a finite element method. This means that the Taguchi design method is very useful for the optimization design of O-ring rectangular groove geometry. Based on the computed FEM results by the Taguchi design technique, the dimensions of a groove geometry are given as h=2.5 mm, d=2.74 mm, c=0.15 mm, and w=3.0 mm. In this study, the initial compression ratio of O-rings is recommended as 8.7% for a gas supply pressure of 18 $kg/cm^2$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.11a
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• pp.249-254
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• 2004

광의 효율적 사용을 위해 표면에 마이크로 그루브가 새겨진 고성능 광학 부품의 개발이 활발하고, 이들 부품의 다량 생산을 위한 초정밀 금형제조기술이 각광을 받고 있다. 최근의 초정밀 미세 기계가공의 경우 간단한 공정으로 이러한 마이크로 그루브 금형을 제작할 수 있다. 특히 조명각 변조용 렌티큘러 렌즈와 같이 실린더형 그루브 금형의 경우에는 기존의 Lithography, MEMS, LIGA 등 광 에너지를 이용한 다른 제조방법들에서는 가공하기 어려운 점이 있으나, 기계가공에서는 쉽게 제작가능한 장점이 있다. 본 연구에서는 이러한 미세기계가공기술의 장점을 활용하여 U 형 마이크로 그루브를 가진 Lenticular 렌즈용 금형을 가공하고자 하였다. 가공에는 3 축 구동의 초정밀 미세 복합가공기와 단결정 천연 다이아몬드공구가 사용되었고, 가공방식은 마이크로 세이핑 공정을 적용하였으며, 가공 금형 재료에는 Brass와 무전해 Nickel이 사용되었다. 실험을 통하여 금형가공시의 절삭력, 칩 형상, 가공표면 등의 분석이 수행되었으며 이를 기반으로 여러 가지 가공문제점을 해결하고, 최종적으로 양호한 렌티큘러렌즈용 금형을 가공하였다.

• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.72-79
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• 2002

In this study, time-dependent distributions of temperature and stresses, in the box-column welded from ultra thick plates with center segregation, has been analyzed by the commercial finite element package SYSWELD+, for several types and angles of groove. The major points of investigation are the optimum type and angle of groove that minimize weld stress specially at the center segregation, as well as temperature distribution, residual stresses and changes in the mechanical properties. The results can be summarized as follows; 1) Generally the thermal cycle at the root of groove exhibits relatively rapid cooling pattern, however, most of the other part weldment have a slow cooling pattern in all groove types. 2) Most of the micro-structures of weldment are composed of ferrite and pearlite, meanwhile we could find martensite and bainite locally a the root of the groove. 3) Optimum groove type for high heat input welding of box-column corner is a double groove type, and the optimum angle for the groove is 30~$45^{\circ}$ that minimize deformation and weld stress at the center segregation.