• 대한기계학회논문집A
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• 제24권6호
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• pp.1491-1498
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• 2000

In recent years, CFRP composite materials have been increasingly used in various fields of engineering because of a high specific strength and stiffness properties. Drilling is one of the most impo rtant cutting processes that are generally carried out on CFRP materials owing to the need for the structural integration. However, delamination are often occurred as one of the drilling damages. Therefore, there are needs studying for the relationships between CFRP drilling and delamination in order to avoid low strength of the structures and inaccuracies of the integration. In this study, AE signals and thrust forces were used for the evaluations of the delamination from a drilling process in [0/900]s CFRP materials. And the drilling damage processes were observed and measured by a real time monitoring technique with a video camera. From the results, we found that the relationships between the delamination from drilling and AE characteristics and drill thrust forces for [0/900]s CFRP composites. Also, we proposed the monitoring method for a visual analysis of drilling damages.

• 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.

• 화약ㆍ발파
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• 제38권1호
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• pp.14-22
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• 2020

천공 중 비트의 손상은 천공 효율을 떨어뜨리는 주요 원인이다. 현재 천공 중 비트의 마모와 손상에 대한 관리는 현장 작업자의 기술에 의지하고 있어 이를 예측하고 관리하는 시스템의 구축이 시급하다. 비트의 정확한 손상 시점을 판단하기 위해 천공 중 발생하는 소음 자료를 이용해 웨이블릿 변환 분석을 하였다. 이를 통해 얻은 시간-주파수 스펙트럼을 분석한 결과 천공 후 652.8 sec에 주파수 500 Hz 구간에서 웨이블릿 변환 값이 0.9로 최대치가 되는 이상점을 확인하였다. 또한, 천공 속도 분석을 통해 이상치가 발견된 후 천공 속도가 평균인 32 mm/s 보다 9 mm/s 줄어든 것을 확인하였다. 이러한 결과를 통해 웨이블릿 변환 분석을 이용해 천공 중 드릴 비트의 손상을 진단할 수 있음을 보였다.

• 동력기계공학회지
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• 제3권2호
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• pp.42-50
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• 1999

In recent years, composite materials like CFRP are increasingly used in various fields of engineering because of their unique properties which offer a high strength/density and high modulus/density. When CFRP structures are manufactured in drilling processes which are frequently practiced in an Industry, they bring on the delaminations sometimes. So, acoustic emission(AE) techniques were used for a condition monitoring of the drilling process in CFRP. In this study, the AE from CFRP estimated the delamination which reduces the strength and load carrying capacity under the drilling process and the initial delamination were well caught and measured by a video camera. From the results, it was found the relationships between failure mechanism of CFRP delamination and AE characteristics as like amplitude and count.

• 한국태양에너지학회 논문집
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• 제31권4호
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• pp.103-111
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• 2011

Laser drilling of vias is the one of key technologies in developing Emitter-Wrap Through(EWT) solar cell which is particularly attractive due to the use of industrial processing and common solar grade p-type silicon materials. While alternative economically feasible drilling process is not available to date, the processing time and laser induced damage should be as small as possible in this process. This paper provides an overview on various factors that should be considered in using the laser via drilling technology for developing highly efficient and industrially applicable EWT solar cells.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.47.1-47
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• 2001

The drilling process has a great importance for the production technology due to its widerspread use in the manufacturing industry. In order to enhance a maximum production rate and prevent the drill from the damage, it is important to monitor and control the drilling system. Thrust force and cutting torque are the main output variables in the design of drilling control systems. In this paper, an alternative estimation method of thrust force by using flexible neural networks is proposed. Flexible neural network uses the sigmoid activation function with adjustable parameter in order to enhance the approximation accuracy ...

• 한국레이저가공학회지
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• 제17권2호
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• pp.5-10
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• 2014

Aluminum has been widely used in the electric applications because of light metals. When mechanical element is periodically moving with contacting other surfaces, the anodizing process for aluminum is useful for avoiding the abrasive damage. The anodized element has quietly different characteristics with respect to the distribution of hardness and crystal structure. In this work, the laser drilling of anodized surface is studied experimentally. Fusion drilling method - laser drilling with inert gas blowing - is used. The effect of various process parameters (gas pressure, laser power, focus position) is investigated with respect to the hole size and circularity.

• 한국정밀공학회지
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• 제12권8호
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• pp.27-38
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• 1995

For solving troubles happened during the drilling process with carbon fiber epoxy composite materials(CFRP) by using HSS drill, a few types of diamond gift electroplated drills are manufactured, and machinability of these drills is experimented with a variety of cutting speed and feed rate. These drills have some advantages of good wear resistant and the conception of grinding process. As a result, using of these drills improves both troubles being caused by tool wear and damage of exit surface depending on fiber stacking angle. It is desirable that cutting conditions for the cutting thickness per revolution must be set under 0.01mm when the size of a diamond grit is # 60 .approx. 80.

• 한국해양공학회지
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• 제34권2호
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• pp.110-119
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• 2020

Explosions and fires on offshore drilling units and process plants, which cause loss of life and environmental damage, have been studied extensively. However, research on drilling units increased only after the 2010 Deepwater Horizon accident in the Gulf of Mexico. A major reason for explosions and fires on a drilling unit is blowout, which is caused by a failure to control the high temperatures and pressures upstream of the offshore underwater well. The area susceptible to explosion and fire due to blowout is the drill floor, which supports the main drilling system. Structural instability and collapse of the drill floor can threaten the structural integrity of the entire unit. This study simulates the behavior of fire subsequent to blowout and assesses the thermal load. A heat transfer structure analysis of the drill floor was carried out using the assessed thermal load, and the risk was noted. In order to maintain the structural integrity of the drill floor, passive fire protection of certain areas was recommended.

• 산업공학
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• 제7권3호
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• pp.155-168
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• 1994

In computer integrated manufacturing environment, tool management plays an important role in controlling tool performance for machining operations. Knowledge of tool behavior during the cutting process and effective tool-behavior prediction contribute to controlling machine costs by avioding production delays and off-target parts due to tool failure. The purpose of this paper is to review and develop the tool condition monitoring scheme for drilling operation to assure a fast corrective response to minimize the damage if tool failures occur. If one desires to maximize system through-put and product quality as well as tooling resources, within an economic environment, real-time tool sensing system and information processing system can be coupled to provide the necessary information for the effective tool management. The example is demonstrated as to drilling operation when the aluminum composites are drilled with carbide-tipped HSS drill bits. The example above is limited to the situation that the tool failure mode of drill bits is wear.