• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.482-485
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• 2002

Development projects in KAIST rotted to the micro thermal device is introduced. Multi disciplinary research team is composed by combustion group and semiconductor group in KAIST and catalyst research center in KRICT to develop micro thermal/fluidic device and various items are on development. Among the projects, various kind of componenst that is required by the micro thermal devicesystem is introduced. Technology related to development of micro combustor, Micro igniter, micro fabrication of 3D structure, micro reactor and micro catalyst preparation is introduced.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.368-371
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• 2008

An extensometer system to measure strain and displacement of cylindrical fatigue specimen in a autoclave of high temperature and high pressure environment has been developed by KEPRI. The extensometer reads the displacement caused by fatigue loads at the target length of the specimen installed inside the autoclave. The performance of the extensometer were tested at 15MPa, $315^{\circ}C$ of a operating pressurized water reactor. Two LVDT's of magnet type were connected to the extensometer and used for converting the fatigue displacement to electronic signal. The device is being used for developing environmental fatigue curve of CF8M cast austenitic stainless steel (CASS) in the test condition of low cycle and low strain. This paper introduces the background and results of the development.

• Journal of the KSME
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• v.30 no.3
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• pp.246-251
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• 1990

마이크로폴라 탄성이론은 다른 마이크로연속체(microcontinuum) 이론에 비해 적용이 간단하며, 실제 많은 물리적인 현상을 규명하는 데 다양하게 이용할 수 있다. 특히 고전 탄성이론에 의해 적절하게 해결될 수 없는 덤벨(dumbell) 분자로 이루어진 물체, 액체 결정체(liquid crystals), 과립상(granular)의 분자로 구성된 물체와 복합 섬유재료(composite fibrous materials) 등은 마 이크로폴라 탄성이론에 의해 잘 해결될 수 있다. 또한 마이크로폴라 탄성이론은 고체 내에서의 파의 전파(propagation)와 분산(dispersion), 구멍 주위의 응력집중과 외부 하중을 받는 물체에 있어 균열끝에서의 응력 분포 등의 고체역학 문제들은 물론이고, 경계층(boundary layer), 난 류(turbulence), 유체 유동의 불안정(instability)과 표면장력 현상 등의 유체역학에서의 복잡한 문제들을 해결하는 데에도 이용할 수 있다. 마이크로폴라 탄성이론은 고전 탄성이론에 비해 상 대적으로 새롭고 미개척 분야이긴 하지만 이론의 기반이 확고하기 때문에 앞으로의 회전응력 측정장치의 개발을 통해 미소구조의 영향을 고려해야 하는 많은 문제들을 해결하는데 큰 기여를 할 것으로 전망된다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.292-298
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• 1991

Previous studies on the performance of the round type impactor were reexamined and extended to the case of high particle mass loading. It was pointed out that the previous numerical studies need to be supplemented in the numerical process. The impactor performance was calculated under the same conditions as previous studies by the exact calculation process and it was found out that a tail of the collection efficiency curve, which have not been found in the previous studies, appeared in the results of ours. Numerical results for high particle mass loading show that the value of the collection efficiency in the impactor decreases but better particle-cut characteristics can be obtained, as the amount of the particle mass loading increases.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.121-128
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• 2005

Solder joints in microelectronic devices are frequently operated at an elevated temperature in service. They also experience plastic deformation caused by temperature excursion and difference in thermal expansion coefficients. Deformed solders can go through a recovery and recrystallization process at an elevated temperature, which would alter their microstructure and mechanical properties. In this study, to predict the changes in mechanical properties of Pb-free solder joints at high temperatures, the high temperature microhardness of several Pb-free and composite solders was measured as a function of temperature, deformation, and annealing condition. Solder alleys investigated include pure Sn, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, Sn-2.8Ag-7.0Cu (composite), and Sn-2.7Ag-4.9Cu-2.9Ni (composite). Numbers are all in wt.$\%$ unless specified otherwise. Solder pellets were cast at two cooling rates (0.4 and $7^{\circ}C$/s). The pellets were compressively deformed by $30\%$ and $50\%$ and annealed at $150^{\circ}C$ for 2 days. The microhardness was measured as a function of indentation temperature from 25 to $130^{\circ}C$. Their microstructure was also evaluated to correlate with the changes in microhardness.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.55-59
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• 2003

In this study, $Al_xTa_{1-x}$(x=0.0∼1.0) alloy thin films were grown by RF-Magnetron sputtering system, and the structural, mechanical and electrical properties of samples were examined by 4-point probe, XRD, AFM and micro-Vickers hardness profiler. The electrical resistivity was maximum and the crystal quality was optimum for the samples with Al content x=0.245 (Al 24.5 at.%). Regarding the surface hillock formation, the hillock density decreased with an increase of Al content for the low Al content range, and the hillock was eliminated for the sample with Al=24.5 at.%. The hillock density increased with the further increase of Al content. The high values of micro-Vickers hardness were obtained for the samples with x=0.2∼0.45. The results obtained demonstrate that the crystal quality, electrical resistivity, surface morphology and micro-hardness are closely inter-related, and that the optimum physical properties are obtained for the sample with x=0.245.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.107-119
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• 1991

This dissertation analyzes the running mechanism of flexible and thin tape above rotating head through the experiment. The scope of study is confined to measure the vertical deformation of running tape under hydrodynamic pressure invoking phenomena of elasto-hydrodynamic lubrication between the protruded bump on a rotating cylinder ad the running tape. Experimental system is devised to measure the vertical deflection of the running tape by opto-electronical displacement gauge, which enables to detect microscopic surface deflection of high frequency. Thorough the tests of small specimens of groove and bump, the accuracy and reliability of this experimental method is confirmed and achieved an accuracy within 5%(2.mu.m) error for the microscopic deflection with high frequency. In experimental works, the effects of bump size on flying characteristics of the tape were evaluated and examined. For the vertical deformation of the running tape. the numerical results and its trend agree qualitatively with the experimental ones.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.125-125
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• 2013

기계부품 및 자동차부품 등의 내마모나 내피로성의 향상을 위한 표면처리로서 고주파처리, 침탄처리, 질화처리 등이 사용되고 있다. 최근에는 변형을 최소화 함으로써 후가공을 생략할 수 있는 질화처리가 주목받고 있다. 질화처리종류로는 염욕질화나 가스질화법이 사용되고 있으나, 이들에 비해 환경오염 및 공해가 적고 인체에 무해한 플라즈마 연질화법이 사용되고 있다. 플라즈마 연질화 기술은 IT기기의 제품에 적용되는 표면경화의 공정개발은 미비한 실정이다. 마이크로 구동 요소 부품중의 하나인 Leadscrew는 이송장치를 구성하는 핵심 부품으로 IT기기의 정밀 이송 및 구동제어에 사용되는 핵심 부품으로 사용되고 있으며, 리드스크류의 소재인 SWCH1018A(냉간압조용강선)은 표면 경도가 낮고 변형이 쉽기 때문에 표면 경화를 위한 플라즈마 연질화 기술을 이용하고자 했다. 본 연구는 플라즈마 연질화 공정을 적용한 시편의 표면경도를 높혀주고 변형을 최소화 할 수 있는 공정을 확인하는 것이다. 공정변수를 변화 시키면서 얻어진 시편의 표면미세 구조를 미소경도측정, XRD, SEM분석을 통하여 확인하였으며, 이를 통해 시편 표면경도를 높여주는 공정 조건을 도출하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.183-193
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• 2003

Micro-weighing device by using null balance method is being essential part in fields of high-technology industries such as precision semiconductor industry, precision chemistry, biotechnology and genetics etc. Also, requirements for high resolution and for large measurement range increase more and more. The performance of the micro-weighing device can be determined by the mechanism design and analysis. The analytical design method has been proposed for the performance improvement such as resolution, measurement range and fast response. The 2-stage displacement amplification is designed to overcome the limit of conventional force transmitting lever. The parallel spring is designed for the measurement result independent of the input force position variation. Also, the natural frequency of mechanism is analyzed for the fast response. After each analysis, optimal design has been carried out. To verify the analysis and design result, characteristics experiments had been carried out after construction. Finally, the system had been controlled.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1246-1251
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• 2003

The fracture behaviors of Zr-based bulk amorphous metals(BAMs) having compositions of $Zr_{55}Al_{10}Ni_{5}Cu_{30}$, were investigated under impact loading and quasi-static conditions. For experiments, a newly devised instrumented impact testing apparatus and the subsize Charpy specimens were used. The influences of loading rate and the notch shape on the fracture behavior of the Zr-based BAM were examined. The Zr-based BAMs showed an elastic deformation behavior without any plastic deformation on it before fracture. Most fracture energies were absorbed in the process of the crack initiation. The maximum load and fracture absorbed energy under quasi-static condition were larger than those under impact condition. However, there existed relatively insignificant notch shape effect. Fracture surfaces under impact loading were smoother than those under quasi-static loading. The absorbed fracture energy appeared differently depending on the extent of the vein-like pattern region due to the shear bands developed at the notch tip. It can be found that the fracture energy of the Zr-Al-Ni-Cu alloy is closely related with the development of shear bands during fracture.