• Proceedings of the KAIS Fall Conference
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• 2002.11a
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• pp.260-262
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• 2002

제품의 소재를 미리 테입 형태로 만들어 단면의 경계면을 따라 레이저로 절단하여 적층하는 방식은 제품의 표면에 계단 모양의 무늬가 생기므로 정밀한 제품을 제작하는데 어려움이 있었다. 이를 극복하기 위하여 단면의 경계선을 절단할 때 수직으로 절단하는 것이 아니라 경사면을 따라 절단하여 전체적인 제품의 옆면이 부드럽게 연결되는 경사절단형 임의형상가공시스템을 개발하였다. 이를 위하여 레이저 5축 경사절단기를 개발하였는데, x축과 y축은 상용화되어 있는 x-y table을 이용하였고 z축은 한 개의 z축 이송대를 이용하였다. 롤과 피치를 위하여는 서보모터 두 개를 이용하여 작업대가 회전할 수 있도록 하였다. 이와 같은 레이저 5축 경사절단기를 개발함으로써 시편의 어느 위치에서든 어느 각도로도 절단이 가능하게 할 수 있었다.

• Journal of the Korean Society for Railway
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• v.7 no.2
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• pp.125-129
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• 2004

This study investigates the fatigue lift estimation of butt weld specimen for the railway vehicle by examining butt weld bead profiles. The butt weld beads, which are welded by semi-robot method, have non-uniform bead profiles described by $\theta$, p and h. The stress concentration factors, K$\_$t/, are changed by different $\theta$, p and h from 1.395 to 2.863. Hence, the sensitivity of K$\_$k/ is changed by each $\theta$, p and h. As $\theta$ becomes lower and p and h become higher, K$\_$t/ increases. The fatigue life can be estimated very closely for the AAY specimens without residual stress using only butt weld bead profiles. But, for the AAN specimens with residual stress, the fatigue life must be estimated by considering both the weld bead profiles and the residual stress data.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.155-160
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• 2008

Using a three-dimensional (3-D) FE analyses, this paper provides the shape optimization of the standard test specimen for the torsion test, as well as a method for analyzing effects of misalignment under the angular and concentric misalignment. For verification, FE analysis is performed, which is designed for the perfectly full-model. To optimize the design shape of the torsion-controlled fatigue test specimen, we performed sensitivity analysis using shape parameters. Additionally, two kinds of misalignment (angular misalignment and concentric misalignment) are applied to the circular and tubular specimens to show effects of misalignments in the FE analysis. The present results will provide valuable information for designing shafts for every kind of mechanical system under torsional force.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.10
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• pp.57-68
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• 1995

An upper bound elemental technique (UBET) program has been developed to predict forging load, die-cavity filling, preform in non-axisymmetric forging. To analyze the process easily, it is suggested that the deformation is divided into two different parts. Those are axisymmetric part in corner, plane-strain part in lateral. The plane-strain and axisymmetric parts are combined by building block method. And the total energy is computed through combination of three deformation parts. A dumbbell-type preform has been obtained from height and volumetric compensations of the billet based on the backward simulation. Experimetns have been carried out with pure plasticine at room temperature. Theoretical predictions are in good agreement with expereimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.10a
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• pp.93-97
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• 1993

방진고무는 진동을 방지하여 다른 구조물의 진동전달 차단은 물론, 장비의 수명연장 및 효율을 증가시키기 위한 목적으로 사용되는데 이러한 방진고무 의 동적특성을 일반화하는 것은 어렵기 때문에 방진고무 시편의 동특성 해 석시험 결과치를 기준으로 원하는 성능에 부합하도록 방진고무의 재질을 선 정하고 사양에 의한 엔진마운트를 설계 제작하여야 한다. 이번에 제작한 UEM 엔진마운트는 해상용, 육상용 설비에 적용 가능하며, 특히 해상용에 적 용하고 외부 환경에 의한 부식으로부터 방진고무 및 기자재를 보호하기 위 하여 하우징을 특수재질로 제작하였고, 수직.수평력을 고려하여 큰 하중에 견딜 수 있도록 원추형 형상설계와 강성을 보강하였다. 특히, 원추형 형상으 로 제작하여 하중을 일정하게 분산시키고, 사용 가능한 선형영역을 확대 시 켰으며, Buffer(Steel Bar)를 이용하여 높은 파고 등에 의한 외부 충격량에 따른 큰 변위의 발생으로부터 설비를 보호할 수 있다. 본 논문에서는 물리적 특성이 같은 방진고무를 사용하고, 적층 수만 다르도록 두가지 모델 UEM-155와 UEM-255를 설계 제작하여 수직.수평방향의 정적시험, 동적시 험, 현장 장착시험 등을 수행함으로써 기업에서 요구한 사양에 적합한가를 고찰하였다.

• The Journal of the Acoustical Society of Korea
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• v.34 no.4
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• pp.264-273
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• 2015

Improvement of the radiation beam profile of a medical ultrasonic transducer has been researched in this paper. In order to improve the beam profile, a new transducer structure has been devised that includes both a shaded electrode and a multi-focus lens. For a linear sound source, the beam profile was investigated through finite element analysis, and then the optimal design of the devised structure was carried out by considering such performances as sidelobe level, focal range and beamwidth simultaneously. In the process, the optimal dimension of the devised structure was derived by using the ratio of the focal range to the minimum beamwidth as a performance index. As a result, the beam profile has been improved to have a lower sidelobe level at -20.2 dB and a consistent narrow beamwidth from 30 mm to 160 mm depth with the minimum beamwidth at 2.04 mm. Further, a prototype transducer was fabricated to have the devised structure, and its performance was measured and compared with the analysis results to confirm the validity of the devised transducer structure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.725-731
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• 1985

In this study the rigid-plastic finite element method is used in order to study the deformation characteristics of solid cylinder upsetting. The effects of friction and aspect ratios on the effective strain distribution, axial stresses at the die-material interface, radial displacements, strain components, grid distortion on the meridional cross-section and gradual changes of outer profile are studied analyzed and compared with the experiments for commercially pure aluminum and .alpha.-brass. The agreement between numerical (or theoretical)and experimental results is shown to be acceptable for the engineering purpose.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.51-55
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• 2007

Nickel iron (Ni-Fe) alloy coating was investigated. The effects of the current density, current type, pulse duration and bath compositions on the morphologies and surface hardness of nickeliron deposits as well as the chemical compositions were investigated. The morphologies, surface hardness and chemical compositions of nickel-iron deposits were varied with current density, current type and bath compositions. The surface hardness was increased up to $550{\sim}600Hv$ when PC plating was employed. Crackless coating was obtained when saccharin was added. The change of composition with thickness was analyzed with EDS and FESEM.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.12
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• pp.967-974
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• 2013

Recently the authors had proposed the z-pinning patch concept to simply manufacture z-pinned composite structures at industrial production site and manufactured composite single-lap shear joint specimens using the concept. Through static tensile test on the specimens they had obtained 54~68% improvement of the joint strength. As a sequential study of it, in this study, fatigue test has performed to measure an improvement of joint strength under cyclic loading. The z-pin's material is stainless steel and its surface was specially machined into zagged shapes and chemically corroded to increase the connection force with composite materials. Approximately 98~125% improvement of the joint strength under cyclic loading was obtained.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.1
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• pp.1-6
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• 2003

A novel Solid Freeform Fabrication System, which makes prototype by cutting tapes at the boundary of object and accumulating the tapes, has been developed. In order to overcome the staircase shape at the surface of prototype, the laser beam is irradiated tangent to the surface. Five axis cutting system and the tangent cutting trajectory generation algorithm have been developed.