• 한국CDE학회논문집
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• 제3권2호
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• pp.103-112
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• 1998

In this paper insertion of numerous control points to be performed by using the Chebyshev polynomial root at the selection of knot vector. This method introduces a simple method of knot refinement and it is applied in a developed program. The Chebyshev roots exist densely in broth ends of the range and are proposed more effective knot refinement to modify a surface. Therefore, generated control points are relatively uniform in specified knot interval. In the surface generation, a local insertion of numerous control points are easily inserted by using the characteristic of Chebyshev polynomial roots at knot refinement. It is possible to create a complex surface with a single surface. The number of control point can be reduced by using the local insertion of control points in a required shape

• 한국표면공학회지
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• 제23권1호
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• pp.1-7
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• 1990

Ion implantation is a well established superior superior surface modification technique for the improvement of wear resistance, hardenece, hardness, corrosion resistance, biocompaibity, surface friction, as well as for the modification of surface electric conductance. Conventional ion implantaion is a line-of-sight process witch ues the ion beam accelerator techniques. Plasma sheath ion implantation (PSII), as a new technique, is described in this paper. In PSII high voltage pulse is applied to a target material placed directly in a plasma, forming a think ion-matrix sheath around the target. Ions accelerate through the sheath drop and bombard the traget from all sides simultaneosuslyregardless of the target shape. This paper describes the principle of PSII, which has non-line-of sight characteristics, as well as the experimental appratus.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.243-251
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• 1998

A method of establishing the tooth modification for gear transmission of vehicles to reduce gear whine noise, caused by tooth impact phenomenon of mating gear, is introduced. The major causes of tooth impact are due to the deflections of gear teeth and shafts of transmission with the loaded condition including various kinds of manufacturing errors. The theoretical shape of tooth surface to avoid tooth impact is derived by the amount of elastic deformation of gear teeth and shaft and overall manufacturing error of machine tool. The surface function is converted with respect to the conventional commercial data usually communicated to the gear inspection system. The proposed method is applied to the gearbox of four wheel drive vehicle and shows the gear whine noise decreased to the 8 dB in the sound level.

• 한국전기전자재료학회논문지
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• 제19권3호
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• pp.233-239
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• 2006

Two different nanofluids were prepared by dispersing $Al_{2}O_3$ nanoparticles in transformer oil after hydrophobic surface modification. The agglomerated alumina nanoparticles with diameters from ${\mu}m$ to mm were ball-milled and then treated with surfactants such as lauric acid, stearic acid and oleic acid. The surface characteristics of modified nanoparticles were examined by FTIR spectroscopy. It showed that the hydrophobicity of nanoparticles was caused by esterification between hydroxyl groups on the particle surface and functional groups of surfactant. The shape and size distribution of ball-milled particles were analyzed by TEM and PSA. The results compared with the primary particles indicated that the size distributions of nanoparticles were dependant on milling times. The dispersion stability of modified nanoparticles dispersed in oil was highly dependent on the composition and amounts of surfactants.

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.71-73
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• 2008

The development of polymer/inorganic nanocomposites has attracted a great deal of interest due to the improved hybrid properties derived from the two different components. Various nanoscale fillers have been used to enhance polymer mechanical and thermal properties, such as toughness, stiffness, and heat resistance. The effects of the filler on the final properties of the nanocomposites are highly dependent on the filler shape, particle size, aggregate size, surface characteristics, polymer/inorganic interactions, and degree of dispersion. In this paper, we describe the influence of different $CaCO_3$ dispersion methods on the thermal properties of polyethylene terephthalate (PET)/$CaCO_3$ composites: i.e., the adsorption of $CaCO_3$ on the modified PET surface, and the hydrophobic modification of the hydrophilic $CaCO_3$ surface. We prepared PET/$CaCO_3$ nanocomposites using a twin-screw extruder, and investigated their thermal properties and morphology.

• Tribology and Lubricants
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• 제15권3호
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• pp.265-271
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• 1999

Wherever there are rotating equipment and contact between surface, there is wear and the generation of wear particles. The particles contained in the lubricating oil carry detailed and important information about the condition monitoring of the machine. This information may be deduced from particle shape, composition, size distribution, and concentration. Therefore, This paper was undertaken to Ferrography system of wear debris generated from lubricated moving machine surface. The lubricating wear test was performed under different experimental conditions using the Falex wear test of Pin and V-Block type by Ti(C, N) coated. It was shown from the test results that wear particle concentration (WPC) and wear severity Index( $I_{S}$), size distribution in normal and abnormal wear have come out all the higher value by increases sliding friction time. Wear shape is observed on the Ferrogram it was discovered a thin leaf wear debris as well as ball and plate type wear particles. This kind of large wear shape have an important effect not only metals damage, but also seizure phenomenon.

• 한국기계가공학회지
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• 제17권6호
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• pp.68-74
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• 2018

Study on the Ti-6Al-4V have been carried out using cutting simulation, and researches for cutting force and chip shape prediction have been actively conducted under various conditions. However, a 3D printer application method using Ti-6Al-4V metal powder material as a high-power method has been studied for the purpose of prototyping, mold modification and product modification while lowering material removal rate. However, in the case of products / parts made of 3D printers using powder materials, problems may occur in the contact surface during tolerance management and assembly due to the degradation of the surface quality. As a result, even if a 3D printer is applied, post-processing through cutting is essential for surface quality improvement and tolerance management. In the cutting simulation, the cutting force and the chip shape were predicted based on the Johnson-Cook composition equation, but the shape of the shear type chip was not predictable. To solve this problem, we added a damaging term or strain softening term to the Johnson-Cook constitutive equation to predict chip shape. In this thesis, we applied the constant value of the S-K equations to the cutting simulation to predict the cutting force and compare with the experimental data to verify the validity of the cutting simulation and analyzed the machining characterization by considering conditions.

• 연구논문집
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• 통권26호
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• pp.121-132
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• 1996

The carburising surface modification treatment of the die steel has been used for improving wear resistance and heat cycle strength of the die and preventing a pitting on the surface because the carbides are forming in the matrix during carburising. Generally, the hot forging die was used after quenching-tempering treatment or nitriding after quenching-tempering treatment. The nitriding after carburising on the surface of a hot die steel and a wear resistance die steels was suggested by SOUCHARD, JACQUOT. and BUVRON. This surface modification treatment improved the adhesive and abrasive wear resistance and friction coefficient. The process was introduced to the forging die of stainless steel, titanium alloy steel, alloy and medium carbon steel and the physical properties of the die after the treatment were improved. The surface hardening treatment of the nitriding, the carburising, the boriding, and TD process were used to improved the life time of the forging die. Also, the coating process of PVD, CVD and PCVD were used and the hard chromium plating was occasionally used. Therefore, this study analyzed the effects of the carburising time and the conditions of nitriding on STD61 steel. The case depth, the surface hardness, the forming carbide size and shape during overcarburising process on the die steel were also examined.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.259-262
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• 2005

Numerous studies showed that safety and serviceability of many concrete infrastructures and buildings built in 1970's have capacity less than their design capacities and thereby require immediate retrofitting. Currently, these aged concrete structure are being repaired using many repair and strengthening methods developed in the past. Therefore, in this study, a repairing and strengthening method for retrofitting high strength concrete columns that can effectively improve the performance of high strength concrete columns is developed. The square high strength concrete column's cross-sectional shape is modified to octagonal shape by attaching precast members on the surface of the column. Then, the octagonal column surface is wrapped using Carbon Fiber Sheets (CFS). The method allowed the maximum usage of confinement effect of externally wrapped CFS, which resulted in improved strength and ductility of repaired high strength concrete columns.

• 한국정보과학회논문지:시스템및이론
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• 제33권4호
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• pp.205-215
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• 2006

LCB 타블렛과 타블렛 PC 등과 같은 펜-입력 디스플레이는 CAD에서, 특히, 컨셉트 디자인 단계에서 유용하게 사용될 수 있다. 본 논문에서는, 이런 장치들을 대상으로 하는 CAD 시스템에서 사용될 수 있는 직관적인 B-Spline 수정 방법을 제안한다. 컨트롤 포인트를 기반으로 하는 B-Spline 수정 방법과는 달리, 본 논문에서 제안한 방법은 곡선이나 곡면의 최종적인 모양을 결정하는데 사용자의 펜 입력을 이용한다. 이전에 방법에서 컨트롤 포인트나 조작자(manipulator)를 이용했던 것에 비해 원하는 모양을 만들어 가는 데 소요되는 시간을 줄여준다. 이런 과정은 디자인을 하는데 있어서 지금까지는 피할 수 없는 것처럼 여겨져 왔다. 본 논문에서 제시된 방법의 용이성을 검증하기 위하여 여러 명의 디자이너들과 함께 실험을 수행한 결과를 보여준다.