• 한국정밀공학회지
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• 제16권7호
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• pp.7-14
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• 1999

어브레시브 워터젯을 이용한 Drilling시 깊이에 대한 예측은 가장 중요한 변주중의 하나다. 이 논문에서는 구멍 깊이의 예측 및 구멍 형상을 연구하기 위하여 3차원 해석 모델이 제안되었다. 해석 모델은 크게 두 가지로 구성되었다. 하나는 비선형 반복 방정식에서 생성된 입자의 운동식이며, 다른 하나는 수많은 입자에 의한 충돌시 가공능력을 규정지우는 Constitutive Equation으로 구성되었다. 이 모델은 구멍 가공이 진행됨에 따라 발생하는 감쇠 효과를 고려하였다.실험적인 고찰이 해석모델의 유용성을 검증하기 위하여 이루어졌으며, 근사한 결과를 보였다.

• 한국시뮬레이션학회논문지
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• 제20권2호
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• pp.11-17
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• 2011

본 논문은 해양구조물 rig의 굴착시스템의 하부 부분의 3차원 모델링과 굴착과정의 시뮬레이션에 있다. 최근 조선사들은 높은 부가가치성과 신조의 감소로 인해 해양구조물 rig에 관심이 집중되고 있다. 그러나 대부분의 경우 해양구조물 rig의 기본 설계, 설치 및 운영은 외국회사들이 수행하고 있다. 따라서 굴착에 대한 지식과 정보를 얻기가 쉽지 않다. 본 논문에서는 해양구조물 rig의 핵심장비로 굴착장비, 폭발방지장치인 BOP, 시멘트 작업 및 머드 순환 장치 관련 장비들을 포함하였다. 이들의 구조와 기능은 객체지향기술 관점에서 분석하였다. 이 분석에 기초하여 3차원 소프트웨어 도구인 CATIA와 3DVIA Composer 를 이용하여 이 장비들을 모델링하였다. 굴착과정은 굴착작업의 시나리오에 따라 시뮬레이션되었다. 이 시뮬레이션 시스템은 해양플랜트 산업분야의 엔지니어와 학생들에게 교육도구로 유용하게 활용될 수 있다.

• International Journal of Precision Engineering and Manufacturing
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• 제2권1호
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• pp.11-17
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• 2001

In drilling of composite laminates, it is important to minimize of reduce occurrences of delaminations. In particular, a peel -up delamination at entrance and push-up delamination at exit are common. Deleaminations may by avoided by regulating the drill thrust force can be controlled by adjusting the feedrate of the drill. Dynamics involved in drilling of composite laminates is time varying and nonlinear. In this paper, a fuzzy logic model and control strategy are proposed. Simulation results show that the fuzzy model can describe the nonlinear time-varying process well. The fuzzy controller realizes a fast rise time and a little overshoot of drilling force.

• 한국안전학회지
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• 제16권4호
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• pp.47-51
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• 2001

The carbon fiber reinforced plastics(CFRP) have been widely used in aircraft and spacecraft structures as well as sports goods because it has high specific strength, high specific stiffness and low coefficient of thermal expansion. Machining of CFRP poses problems not frequently seen for metals due to the nonhomogeneity, anisotropy, and abrasive characteristics of CFRP. Delamination is a common problem faced while drilling holes in CFRP using conventional drilling. Therefore, AE characteristics related to drilling damage process of unidirectional and [0/90/]s crossply laminate composite was studied. Also drilling damage like the delamination was observed by video camera in real time monitoring technique. From the results, we basically found the relationships between the delamination from drilling and AE characteristics for CFRP composites.

• Journal of Advanced Marine Engineering and Technology
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• 제18권4호
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• pp.62-68
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• 1994

Recently, the trends toward reduction in size and weight of industrial products increased the application of micro hole for manufacturing gadgets of high precision and gave rise to a great deal of interest for micro hole drilling M/C. Quite a few research work is performed on micro drilling on domestic basis compared with the tendency of analyzing cutting mechanism, adaptive control, monitoring of generally available drills of diameter greater than 1mm. This study adresses the design, manufacturing and controlling a micro hole drilling M/C with the overload detection instrument and the step feed mechanism. Controlling and monitoring of the drilling process are acomplished on PC basis for more user interfaces and effectiveness. The test machine of the results of this research shows a good foundation for extending further micro hole machining technique.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 춘계학술대회 논문집
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• pp.6-11
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• 1997

In most machining operations, undesirable burr are formed on the edge of the workpiece adjacent to the machined surface. Such burrs are often the cause of various problems during automatic maching process. Therefore, it is very important to know characteristics of burr formation in maching process. This paper describes characteristic of exit burrs generated during miniature drilling process. In particular, the effect of spindle speed, feedrate and drill diameter on burr formaton is investigated. The result showed that exit burr height increased significantly with increasing feedrate.

• 대한치과의사협회지
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• 제53권5호
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• pp.368-376
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• 2015

Purpose : The objective of this research was to develop a more simplified drilling procedure with an enhanced implant drill. Materials and Methods : The drill enhanced design factors enabled implantation of Dia. 5.0mm fixture with only 2 times drilling which is more simplified drilling procedure. The enhanced drill was designed with 2 flutes, 2-phase or 3-phase formed drill tip and 25 degrees of helix angle. The proposed drilling procedure (2 times) was compared with a general drilling process (4 times) in terms of temperature changes, cutting time and ISQ value. Results : The simplified drilling procedure indicated less heat than a conventional drilling procedure (p<0.05). The enhanced drill showed significantly shorter drilling time than a conventional drill (p<0.05). On the other hand, higher insertion torque and ISQ value were observed on the the suggested drilling procedure than the conventional drilling procedure (p<0.05). Conclusion : A simplified drilling procedure with the newly designed drill could provide higher effectiveness and safety of dental implant operations under properly controlled external conditions, such as irrigation and RPM of drilling.

• 터널과지하공간
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• 제24권5호
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• pp.386-394
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• 2014

발파를 이용한 채광작업에 있어서 천공의 정확성은 발파의 효율성을 결정할 수 있는 중요한 요소 중의 하나이며, 따라서 천공오차의 발생 원인에 대한 분석과 천공오차의 발생 정도를 줄일 수 있는 대책 마련은 발파의 효율성 및 안전성 확보에서 매우 중요하다. 본 연구에서는 천공오차의 발생 원인을 제어가능 요인과 제어불가능 요인으로 나누어 분석하였으며 현장조사와 AHP 분석을 통하여 천공오차를 유발하는 요인들의 영향성을 살펴보았다. 또한 이들 간의 가중치 분석을 통해 천공오차를 낮출 수 있는 효과적인 대책을 제시하였다.

• Geomechanics and Engineering
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• 제7권5호
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• pp.553-567
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• 2014

Borehole instability during drilling process occurs frequently when drilling through shale formation. When a borehole is drilled in shale formation, the low permeability leads to an undrained loading condition. The pore pressure in the compressed area near the borehole may be higher than the initial pore pressure. However, the excess pore pressure caused by stress concentration was not considered in traditional borehole stability models. In this study, the calculation model of excess pore pressure induced by drilling was obtained with the introduction of Henkel's excess pore pressure theory. Combined with Mohr-Coulumb strength criterion, the calculation model of collapse pressure of shale in undrained condition is obtained. Furthermore, the variation of excess pore pressure and effective stress on the borehole wall is analyzed, and the influence of Skempton's pore pressure parameter on collapse pressure is also analyzed. The excess pore pressure decreases with the increasing of drilling fluid density; the excess pore pressure and collapse pressure both increase with the increasing of Skempton's pore pressure parameter. The study results provide a reference for determining drilling fluid density when drilling in shale formation.

• 한국기계가공학회지
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• 제17권3호
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• pp.7-15
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• 2018

Drilling processes require a cutting monitoring function that can be analyzed and gives feedback about strange conditions, tool collision and tool wear in real time. In this study, we proposed a drill monitor using the torque from the main spindle in CNC machine tools and a PROFIBUS network as a PLC-based interface. This paper studied drilling torque changes depending on drill size, the repetition cutting of the drilling and the drill's wear in the same cutting conditions. The material of the drills was high speed steel (HSS) and uncoated. The drills chosen were 2.7 mm, 6.7 mm, and 10.0 mm in diameter. These drills were selected because they had basic holes for their taps.