• 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.

• Fire Science and Engineering
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• v.27 no.6
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• pp.38-43
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• 2013

As a preliminary study to evaluate the reliability of the calculation method of fire load for residential furniture combustibles, the present study estimates the fire load considering the volume data obtained by the 3D geometrical information of combustibles and material properties based on the literature survey and sample burning test. A kitchen sink cabinet, couch and workstation were investigated for estimating its fire load and real fire test have been performed to measure total energy released from the combustibles. Based on total energy measured from real fire test, the relative error of the estimated fire load due to literature survey and measured material properties showed 6~120% and less than 20%, respectively. It shows that the estimation error of fire load are greatly affected by its material properties as well as geometrical information of combustibles and the present study will be able to contribute to accurate estimation of fire load.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.1
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• pp.52-60
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• 2015

Nuclear power plant contain many dissimilar metal welds that connect carbon steel components with stainless steel pipes using alloy600 welding materials. Primary water stress corrosion cracks at dissimilar metal welds have been continuously reported around the world. In periodic integrity evaluations, dissimilar metal welds are examined using a generic ultrasonic testing procedure, KPD-UT-10. In this procedure, the gap between the probe and examination surface is limited to 1/32 inch (0.8mm). It is not easy to test some dissimilar metal welds in Korean plants applying ordinary technology because of their tapered shapes and irregular surface conditions. This paper introduces a method for applying a flexible phased array technology to improve the reliability of ultrasonic testing results for various shapes and surface conditions. The artificial flaws in specimens with irregular surfaces were completely detected using the flexible phased array ultrasonic technology. Therefore, it can be said that the technology is applicable to field examination.