• 한국정밀공학회지
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• 제8권2호
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• pp.36-46
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• 1991

This study was carried out to investigate the characteristic of dynamic component in drilling. Materials used were carbon steel, brass and cast iron, and the drills used were high speed steel drill and cemented carbide. The cutting resistance generated in drilling was detected with the aid of piez0-electric tool dynamometer which has an excellent frequency response, and then the magnitude and shape of dynamic component and its frequency component as well were analyuzed. After a thorough study of interrelationship, the obtained results are as follows; 1) The shape of torque and thrust of the early drilling are different. 2) The shapes of dynamic component can be classified into four kinds. 3) Torque is related to frequency more closely than thrust. 4) As cutting speed increased, dynamic component increased. 5) Chipping took place continuously, and its size decreased as cutting proceeded.

• 한국기계기술학회지
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• 제13권2호
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• pp.1-7
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• 2011

The CFRP composite has a lot of merits such as mechanical characteristic, light and thermal resistance. For these merits, CFRP is applied to so many industrial area. In order to use the composite materials in the aircraft structures or machine elements, accurate surfaces for bearing mounting or joints must be provided, which require precise, machining. In this study, the specimens differentiating the stacking sequence of 5kinds were used. When drilling the carbon fiber reinforced plastics, it was checked on whether the stacking sequence reached any effect on the cutting force. Also relationship between the drill diameter is examined from the drilling experiment, which is the drilling of Fabric, Unidirectional specimen with ∅6mm, ∅10mm, ∅12mm cemented carbide drill. Considering cutting force and drilling diameter, the results are analyzed.

• 한국기계가공학회지
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• 제21권7호
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• pp.53-63
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• 2022

Recently, the use of aluminum components in the reduction of the vehicle weight to improve fuel efficiency and reduce carbon dioxide emissions has increased. In the aluminum machining cutting process, hole-making is an important process that accounts for 30% of the machining process. Although many studies have been conducted using the continuously advancing hole processing technology, studies on the machinability of the tool depending on the type of chuck on the workpiece are still lacking. In this study, the machining performance of cemented carbide burnishing drills was compared and analyzed according to chuck type. The burnishing drill was used to create a hole in the AL6061 workpiece, and the surface roughness and dimensional accuracy of the hole were examined according to the type of chuck while monitoring the spindle load.

• 한국산학기술학회논문지
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• 제13권2호
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• pp.471-477
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• 2012

SCM420재질의 기어를 담금질을 실시한 후 초경호브(Hob)에 PACVD 코팅처리 후 표면경도가 높은 표면(HRC 60)을 절삭하였다. 코팅처리 없이 난삭재(難削材)로 분류되는 경도가 큰것, 경한 물질을 포함한 것, 강도가 높은 것에 공구수명과 생산성을 향상에는 한계성을 가지고 있다. 이를 개선하기 위해 초경호브에 TiCN코팅처리 전후에 대하여 Skiving 절삭으로 코팅처리 한 호브가 가공성이 좋고, 공구마멸이 적어, 공구수명이 2.5배 증가하는 결과를 얻었다. 실험은 CNC 스카이빙 호빙머신을 이용하여 습식절삭으로 절삭속도와 이송량으로 다양한 조건을 적용하여 공구마멸과 표면거칠기 데이터를 얻었다. 실험결과 조건 2에서(V=200m/min F=0.7mm/rev) Cutting speed가 절삭표면에 Feed Mark가 미세하고, 표면거칠기는 Rmax $4.7{\mu}m$(Ra $1.19{\mu}m$)의 데이터를 얻었다.

• 한국분말재료학회지
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• 제25권3호
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• pp.251-256
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• 2018

We report the feasibility of TaC production via self-propagating high temperature synthesis, and the influence of the initial green compact density on the final composite particle size. Experiments are carried out from a minimum pressure of 0.3 MPa, the pressure at which the initial green body becomes self-standing, up to 3 MPa, the point at which no further combustion occurs. The green density of the pellets varies from 29.99% to 42.97%, as compared with the theoretical density. The increase in green density decreases the powder size of TaC, and the smallest particle size is observed with 1.5 MPa, at $10.36{\mu}m$. Phase analysis results confirm the presence of the TaC phase only. In the range of 0.3-0.5 MPa, traces of unreacted Ta and C residues are detected. However, results also show the presence of only C residue in the matrix within the pressure range of 0.6-3.0 MPa.

• The Journal of Advanced Prosthodontics
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• 제9권2호
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• pp.110-117
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• 2017

PURPOSE. This laboratory study assessed the effect of different dentin cleaning procedures on shear bond strength of resin cements for recementing prosthesis. MATERIALS AND METHODS. A $4{\times}4$ flat surface was prepared on the labial surface of 52 maxillary central incisors. Metal frames ($4{\times}4{\times}1.5mm$) were cast with nickel-chromium alloy. All specimens were randomly divided into 2 groups to be cemented with either Panavia F2.0 (P) or RelyX Ultimate (U) cement. The initial shear bond strength was recorded by Universal Testing Machine at a crosshead speed of 0.5 mm/min. Debonded specimens were randomly allocated into 2 subgroups (n = 13) according to the dentin cleaning procedures for recementation. The residual cement on bonded dentin surfaces was eliminated with either pumice slurry (p) or tungsten carbide bur (c). The restorations were rebonded with the same cement and were subjected to shear test. Data failed the normality test (P < .05), thus were analyzed with Mann Whitney U-test, Wilcoxon signed rank test, and two-way ANOVA after logarithmic transformation (${\alpha}=.05$). RESULTS. The initial shear bond strength of group P was significantly higher than group U (P = .001). Pc and Uc groups presented higher bond strength after recementation compared to the initial bond strength. However, it was significant only in Pc group (P = .034). CONCLUSION. The specimens recemented with Panavia F2.0 provided higher bond strength than RelyX Ultimate cement. Moreover, a tungsten carbide bur was a more efficient method in removing the residual resin cement and increased the bond strength of Panavia F2.0 cement after recementation.

• 한국표면공학회지
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• 제49권3호
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• pp.307-315
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• 2016

The properties of AlTiN films by a cathodic arc deposition process have been studied. Oblique angle deposition has been applied to deposit AlTiN films. AlTiN films have been deposited on stainless steel (SUS304) and cemented carbide (WC) at a substrate temperature of $500^{\circ}C$. AlTiN films were analyzed by scanning electron microscopy, glow-discharge light spectroscopy, micro-vickers hardness, and nanoindenter. When applying a current of 50 A to the cathodic arc source, it showed that the density of macroparticle of AlTiN films was 5 lower than other deposition conditions. With the increase of the bias voltage applied to the substrate up to -150 V, the density of macroparticle was decreased. The change of the $N_2$ flow rate during coating process made no influence on the film properties. For the multi-layered films, the film prepared at oblique angle of $60^{\circ}$ showed the highest hardness of 28 GPa and $H^3/E^2$ index of 0.18. AlTiN films have been shown a good oxidation resistance up to $800^{\circ}C$.

• 한국생산제조학회지
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• 제22권2호
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• pp.268-274
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• 2013

Electric discharge machining drill (EDM-drill) is an efficient process for the fabrication of micro-diameter deep metal hole. As there is non-physical contact between tool (electrode) and workpiece, EDM-drill is widely used to machine the hard machining materials such as high strength steel, cemented carbide, titanium alloys. The electro-thermal energy forces the electrode to wear out together with the workpiece to be machined. The electrode wear occurs inside of a machining hole. and It causes hard to monitor the machining state, which leads the productivity and the quality to decrease. Thus, this study presents a methodology to estimated the electrode wear amount while two coefficients (scale factor and shape factor) of the logarithmic regression model are evaluated from the experiment result. To increase the accuracy of estimation model, the linear transformation method is adopted using the differences of initial electrode wear differences. The estimation model is verified through experiment. The experimental result shows that within minute error, the estimation model is able to predict accurately.

• 한국기계가공학회지
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• 제4권3호
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• pp.32-38
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• 2005

Electrical discharge machining is the method of using thermal energy by electrical discharge. Generally, if the material of workpiece has conductivity even though very hard materials and complicated shape which are difficult to cut such as quenching steel, cemented carbide, diamond and conductive ceramics, the EDM process is favorable one of possible machining processes. But, the process is necessarily required of finish cut and heat treatment because of slow cutting speed, no mirror surface, brittleness and crack due to the residual stress for manufactured goods. In this experimental thesis, the super EDM drilling was developed for high precision semiconductor die steel and for minimization of leadframe width. It was possible to development of EDM drilling machine for high precision semiconductor die with the electrode guide and its modelling and stress analysis. The development of electrode with the copper pipe type was conducted to drill the hole from the diameter of 0.1mm to 3.0mm with the error of from 0.02mm to 0.12mm. From the SEM and EDX analysis, the entrance of the EDM drill was found the resolidification of not only the component of tungsten but also the component of copper.

• 자원리싸이클링
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• 제14권2호
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• pp.43-55
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• 2005

세계의 인구증가와 경제성장에 따라 천연자원 특히 전략금속의 수요가 급격히 증가하고 있다. 국가가 보유하고 있는 자원의 양은 천연자원 뿐 아니라 재활용을 통하여 얻을 수 있는 폐자원을 함께 포함해야 한다. 본 연구에서는 전략금속의 안정적 확보와 폐자원의 효율적 재활용을 위하여 코발트의 국내외 사용현황 등을 조사하였으며 아울러 미국 내에서의 코발트 물질흐름에 대한 자료를 정리하였다. 그 결과 미국에서는 2003년도에 약 8,000톤의 코발트가 사용되었으며 원료로 재사용된 스크랩의 양은 총사용량의 28%인 2,200톤이었다. 미국의 경우 초합금과 촉매의 재활용은 잘 이루어지고 있으나 자석류와 초경합금의 경우 재활용율이 다소 낮음을 알 수 있었다.