• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.930-933
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• 2000

Experimental study was conducted for finding the characteristics of machining precision according to the change of feedrate when ball endmilling of semisphere shape. The values of tool deflection and cutting force were measured simultaneously by the systems of eddy-current sensor and dynamometer. The machining precision was analyzed by roundness values, which were deeply relating with tool deflection and forces. the roundness was decreased in down-milling than in up-milling for each feedrate. As the cutting edge is moved to radius direction on the tool path, the tool deflection and the cutting force were seemed to be decreased. As the tool path was moved downward, the values of roundness, cutting force and tool deflection were obtained better ones. When compared the values of roundness, cutting force and tool deflection for different feedrate, the best machining accuracy was obtained at feed rate of 90mm/min in down-milling.

• 대한산업공학회지
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• 제26권2호
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• pp.95-100
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• 2000

Presented in this paper is a scheme for constructing ball rolling blends of a non-uniform B-spline surface(NUBS) patches. Ball rolling blending is a popular technique for blending between parametric surfaces. Along the "common edge" of a pair of "base surfaces" to be blended, a sequence of "ball positions" is sampled. The radius of the ball may vary along the line. At each sampling point, a ball center point and a pair of ball contact points are computed by applying a Jacobian inversion method. Using ball contact points, the constructing scheme of blend NUBS patches consists three steps; 1) determination of intermediate control vertices; 2) determination of boundary vectors; 3) determination of B-spline control vertices. The proposed blending scheme has been tested in a Omega CAM system and found to be working satisfactorily.

• 한국공작기계학회논문집
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• 제15권6호
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• pp.76-81
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• 2006

In this paper, profile error measurement method of a turbine blade using 3D-scanner is developed. The method begins with scanning the upper and lower sides of the blade on which three small balls are attached, and constructs a solid measurement model by registering the two scanned surfaces. Airfoils are derived from the model at each interval by intersecting it with a plane, and arranged with design airfoils. The $2^2$ factorial design search method is engaged in arranging the two airfoils, from which the main blade parameters including the edge radius are computed. The developed measurement technique is applied to practical blade manufacturing and validates its effectiveness.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1068-1073
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• 2003

Method for contact failure mitigation is studied in this paper. The focus is laid on the contact shape that eventually influences the internal stresses. Contact mechanics is consulted within the frame of plane problem. Hertzian contact, rounded punch and uniform traction profiles are considered. Frictional as well as frictionless contact is also considered. As results, the higher traction profile induced by the rounded punch reveals the greatest among the considered shapes. Therefore, it is suggested to increase the edge radius as large as possible if a contact body of punch shape needs to be designed. It is also found that uniform traction cannot always provide the solution of contact failure mitigation.

• Tribology and Lubricants
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• 제15권4호
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• pp.297-303
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• 1999

O-rings in automotive engines are important components such as a coolant pipe, engine oil circulating lines and fuel injector for sealing that makes efficient performance of the engine. Life cycle of O-rings is effected in environments of the O-ring seal, like that applied pressure, working temperature, precompressed ratio and materials. It is related in extrusion, expansion and fatigue failure of O-rings. In this paper, an pressurized, compressed elastomeric O-ring inserted into a rectangular groove is analysed numerically using the nonlinear finite element method. The calculated FEM results showed that extrusion ratio and contact stress are strongly related to the gap clearance and edge radius of the groove.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.594-596
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• 2000

The best simulation condition for the fiber collimator that uses ball lenses was investigated. This kind of fiber collimator can be used in a Micro-Optical-Cross-Connects(MOXC). MOXC is composed of collimating ball lenses, micro mirrors and single-mode fibers. In order to design a MOXC, it is very important to calculate beam path, beam radius, divergence angle that determines the insertion loss of the MOXC. Since the beam profile from the fiber facet is not exact Gaussian profile, it was found that the simulation condition in which beam waist exists on the fiber facet, ignoring Numerical Aperture(NA), gives best agreement with the experimental results. Beam radii were measured with conventional knife edge method.

• Journal of the Optical Society of Korea
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• 제20권5호
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• pp.593-600
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• 2016

Operation properties, such as output power, beam radius, and crystal temperature rise were investigated in a diode-pumped edge-cooled monolithic Yb:YAG laser with ~ 4 W pumping level. The output power showed saturation behavior because of severe temperature rise and poor spatial overlapping between pump beam and lasing mode. Face cooling geometry by using a sapphire plate was also investigated. No apparent saturation behavior in output power was observed due to the reduced temperature rise, which could be attributed to efficient heat removal through the crystal-sapphire interface.

• Tribology and Lubricants
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• 제28권5호
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• pp.240-245
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• 2012

In this study, we developed a new carrier finger to prevent scratches in a sheet metal forming line. The developed carrier finger was designed to have a streamlined shape with a larger radius of curvature at the edges, as well as a smaller contact area. To evaluate the scratch alleviation effect, a sliding contact analysis and scratch test using the pin on a plate wear tester were conducted for both the old and new carrier fingers. The results show that, for both transverse and longitudinal movements of the strip, the newly designed carrier finger reduces both the friction and scratch depth by its streamlined shape, which decreases the pressure spike at the edge.

• Smart Structures and Systems
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• 제23권4호
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• pp.373-385
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• 2019

A study concerning the strength of brittle materials is presented in this paper. The failure behavior was investigated examining the plane of the crack after the failure and comparing the results obtained with those deriving from the fracture mechanics theory. Although the proposed methods are valid in general for brittle materials, the experiment was performed on glass because the results are more significant for this. Glass elements of various sizes and different edge finishes were subjected to bending tests until collapsing. The bending results were studied in terms of failure load and energy dissipation, and the fracture surfaces were examined by means of microscopic analysis, in which the depth of the flaw and the mirror radius of the fracture were measured and the strength was calculated. These results agreed with those obtained from the fracture mechanics analysis.

• 한국안광학회지
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• 제15권4호
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• pp.355-360
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• 2010

목적: 국내에서 시판되는 안경렌즈의 성능을 분석하고 최적화 설계로 수차가 보정된 안경렌즈를 설계하였다. 방법: 굴절률 1.6의 재질을 갖는 4개 회사의 ${\pm}$5.00D의 구면 렌즈와 비구면 렌즈의 중심두께, 곡률반경, 비구면 계수를 측정하였다. Mitutoyo사의 ID-F150으로 중심두께를 측정하였고, Automation Robotics사의 FOCOVISION(SR-2)를 이용하여 곡률반경을 측정하였다. 비구면 계수는 Taylor Hobson사의 PGI 1240S로 측정하였다. 렌즈 후면부터 눈의 회선점까지의 거리 27 mm, 동공직경 4 mm, 중심시야 $30^{\circ}$에서 적은 양의 수차를 갖는 안경렌즈를 설계하였다. 측정 렌즈보다 Axial height를 짧게 함으로써 미용 상의 이점을 높였다. 설계에는 ORA사의 Code V를 이용했다. 결과: -5.00D 비구면 렌즈는 구면 렌즈보다 비점수차와 왜곡수차는 약간 크게 나타났으나 Axial height가 짧고 가장자리 두께가 감소하여 미용 상의 장점이 있다. +5.00D 비구면 렌즈는 왜곡수차의 성능이 향상되고 (-)렌즈와 마찬가지로 Axial height와 중심두께의 감소로 미용 상의 장점을 확인하였다. 최적화 과정을 통한 전면 비구면 렌즈는 비점수차와 왜곡수차가 측정 구면 렌즈보다 좋은 성능과 미용 상의 장점을 확인할 수 있다. 결론: 국내에서 시판되는 비구면 렌즈는 수차의 성능보다는 미용 상의 장점을 키우는 Axial height의 감소와 두께의 감소에 주안점을 둔전면 비구면 설계가 이뤄지고 있다. 최적화 설계이론을 통해 측정렌즈보다 향상된 수차성능과 미용 상의 이점을 모두 갖는 전면 비구면 안경렌즈의 설계를 하였다. 후면 비구면 렌즈의 설계를 통해 전면 비구면 렌즈보다 향상된 성능을 얻을 수 있음을 기대할 수 있다.