• 한국표면공학회지
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• 제53권6호
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• pp.271-279
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• 2020

Non-ferrous metals, widely used in the mechanical industry, are difficult to machine, particularly by drilling and tapping. Since non-ferrous metals have a strong tendency to adhere to the cutting tool, the tool life is greatly deteriorated. Diamond-like carbon (DLC) is one of the promising candidates to improve the performance and life of cutting tool due to their low frictional property. In this study, a sacrificial DLC layer is applied on the hard nitride coated drill tool to improve the durability. The DLC coatings are fabricated by controlling the acceleration voltage of the linear ion source in the range of 0.6~1.8 kV. As a result, the optimized hardness(20 GPa) and wear resistance(1.4 x 10-8 ㎣/N·m) were obtained at the 1.4 kV. Then, the optimized DLC coating is applied as an sacrificial layer on the hard nitride coating to evaluate the performance and life of cutting tool. The Vickers hardness of the composite coatings were similar to those of the nitride coatings (AlCrN, AlTiSiN), but the friction coefficients were significantly reduced to 0.13 compared to 0.63 of nitride coatings. The drilling test were performed on S55C plate using a drilling machine at rotation speed of 2,500 rpm and penetration rate of 0.25 m/rev. The result showed that the wear width of the composite coated drills were 200 % lower than those of the AlCrN, AlTiSiN coated drills. In addition, the cutting forces of the composite coated drills were 13 and 15 % lower than that of AlCrN, AlTiSiN coated drills, respectively, as it reduced the aluminum clogging. Finally, the application of the DLC sacrificial layer prevents initial chipping through its low friction property and improves drilling quality with efficient chip removal.

• 한국작물학회지
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• 제42권1호
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• pp.14-21
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• 1997

본 시험은 직파재배 유형에 따른 생육 및 수량을 밝히고자 동벼와 농안벼를 공시하여 수행하였던 바 그 결과를 요약하면 다음과 같다. 1. 직파재배 유형간 입수수는 건답평면세조파에서 가장 많았고 무논골뿌림재배에서 적었다. 2. 초기의 경수 증가 속도는 어린모 기계이앙재배가 빨랐으며 유교경비율은 직파재배가 이앙재배보다 낮았다. 3. 출수일수는 직파재배가 어린모 기계이앙재배보다 동진벼는 2∼13일, 농안벼는 10∼18일 길었다. 4. 뿌리의 표층 분포 비율은 담수표면산파>담수표면조파>무논골뿌림>건답평면세 조파>어린모 기계이앙재배 순으로 높았다. 5. 제4절간의 굵기는 재배유형간에 차이가 없었으며 제4절간의 간벽두께는 어린모 기계 이앙재배가 직파재배보다 두꺼웠고 줄기 매몰깊이는 어린모 기계이앙>건답평면세 조파>무논골뿌림>담수표면 조파>담수표면산파 순으로 깊었다. 6. 중심고는 직파재배가 어린모 기계이앙재배보다 높았고 모멘트는 어린모 기계이앙재배가 낮았으며 도복지수는 어린모 기계이앙재배가 가장 낮았고 무논골뿌림, 건답평면세 조파, 담수표면조파, 담수표면산파 순으로 낮았다. 7. 도복은 농안벼에서는 발생하지 않았거나 매우 경미하였으나 동진벼는 담수표면직파>담수표면조파>무논골뿌림>건답직파=어린모 기계이앙의 순으로 도복발생이 심하였다. 8. 수량 구성요소와 수량성은 품종간에는 유의적인 차이가 인정되었으나, 어린모 기계이앙 재배와 직파재배, 그리고 직파재배와 유형간에는 유의적인 차이가 없었다.

• 한국기계가공학회지
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• 제14권2호
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• pp.25-30
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• 2015

This study involved the fabrication of precision machine tools using a polycrystalline diamond tip [sintered PCD and cemented carbide (WC-Co) tip] and WC-Co shanks via diffusion bonding with a paste-type nickel alloy filler metal. Diffusion bonding is a process whereby two materials are pressed together at high temperature and high pressure for a sufficient period of time to allow significant atomic diffusion to occur. For smooth progress, a filler metal of nickel alloy was used at the interface. Optical microscopy images were used to observe the copula of the bonded layer. It was confirmed that cracks occurred near the junction in all cases. The tensile strength of the bond was measured using a universal testing machine (UTM) with WC-Co proportional test specimens.

• Geomechanics and Engineering
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• 제19권1호
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• pp.93-104
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• 2019

Anomalies and/or fractured grounds not detected by the surface geophysical and geological survey performed during design stage may cause significant problems during tunnel excavation. Many studies on prediction methods of the ground condition ahead of the tunnel face have been conducted and applied in tunneling construction sites, such as tunnel seismic profiling and probe drilling. However, most such applications have focused on the drill and blast tunneling method. Few studies have been conducted for mechanized tunneling because of the limitation in the available space to perform prediction tests. This study aims to predict the ground condition ahead of the tunnel face in TBM tunneling by using an electrical resistivity tomography survey. It compared the characteristics of each electrode array and performed an investigation on in-situ tunnel boring machine TBM construction site environments. Numerical simulations for each electrode array were performed, to determine the proper electrode array to predict anomalies ahead of the tunnel face. The results showed that the modified dipole-dipole array is, compared to other arrays, the best for predicting the location and condition of an anomaly. As the borehole becomes longer, the measured data increase accordingly. Therefore, longer boreholes allow a more accurate prediction of the location and status of anomalies and complex grounds.

• 한국정밀공학회지
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• 제30권6호
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• pp.638-643
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• 2013

Laser beam machining (LBM) is fast, contactless and able to machine various materials. So it is used to cut metal, drill holes, weld or pattern the imprinted surface. However, after LBM, there still leave burrs and recast layers around the machined area. In order to remove these unwanted parts, LBM process often uses electrochemical etching (ECE). But, the total thickness of workpiece is reduced because the etching process removes not only burrs and recast layers, but also the entire surface. In this paper, surface coating was performed using enamel after LBM on metal. The recast layer can be selectively removed without decreasing total thickness. Comparing with LBM process only, the surface quality of enamel coating process was better than that. And edge shape was also maintained after ECE.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.649-654
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• 2002

In recent days the more use of CFRP composite is in the airplane, automobile, and sport goods , etc., the more necessity of research on it in this engineering. In this research, the CFRP composite specimen are fabricated by 48 CFRP plies with 8 orientation angles, and the specimens are drilled with 3 tools. The results are analyzed with consideration of cutting force, type of tools and fabrication condition. The specimens with each drilling conditions are also investigated with SEM. The optimal drilling conditions such as drill types and cutting fence with respect to the fabricating condition are studied.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.395-398
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• 2002

This study is to examine the safety by analizing the hardness of bed and the characteristic of vibration to improve basic efficiency of machine-tool of drill-cell which is a high line center. The mistake of existing design was shown through the analysis of 3-D and structure. The purpose of this paper is to draw up a plan to improve performance and to propose the design method through finding out the optimum by analyzing dynamic property of structure in a quantity-way by CAE for a quantity-analogy of dynamic property in design steps.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.438-441
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• 2002

Today, it is concentrating on automation and these appearance of industrial robot has been dealing flexibly with this field. If it is drilling through these industrial robot, it will be a high efficiency of the productivity. Therefore, electric drill is setting on articulated robot with six degree of freedom and the 5 face is drilling as the type of articulated robot by a machine object setting. This study was carried out to get the possibility about drilling as analyzing with experimental frequency, original vibration of robot and appearance of vibration when it is practical drilling.

• 한국생산제조학회지
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• 제7권4호
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• pp.117-122
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• 1998

Glass fiber epoxy composite material is widely used in the structures of aircrafts, robots and other machines because of their high specific strength, high specific stiffness and high damping. In order for the composite materials to be used in the aircraft structures or machine elements, accurate surfaces for bearing mounting or joint must be provided, which require precise machining. In this paper, the machinability of the glass fiber epoxy composite material was experimentally investigated. The results can be summarized as follows : 1. The entrance of hole is very good manufacturing existing, but exit come to occur sever surface exfoliation. 2. The cutting force in drilling of the glass fiber epoxy composite material is decreased as the drilling speed increased. 3. If the glass fiber epoxy composite material is drilling by the standard twist drill, then the hole recommand cutting condition is spindle speed 400∼600rpm, feed 40∼50mm/min.

• 한국기계가공학회지
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• 제2권2호
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• pp.37-44
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• 2003

Composite materials are widely used to make all kinds of machine parts, internal and structural materials of cars, aerospace industries, building structures, ship materials, sporting goods and others. It is worth the while to use composite materials as various substitutions when compared With others. But the use is limited in the field of the mechanical processing because of its difficulties in cutting. The surface roughness of in and out in the hole processing was discussed after cutting the GFRP with HSS drill in the vertical machining center. And it is observed that as it processed more, the powdered chip may be got more than the fluid type long chip.