• 한국정밀공학회지
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• 제15권10호
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• pp.65-72
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• 1998

The BTA drilling chip is better for deep hole drilling than other self-piloting with pad drilling chips because the large length to diameter ratio allows a unique cutting force dispersion and better supplies the high pressure fluid. Therefore the BTA is useful for many tasks, such as coolant hole drilling of large scale dies, as well as tube seat drilling, which is essential for the heat exchanger, and variable component drilling for automobiles. Deep hole drilling has several significant problems, such as hole deviation, hole over-size, circularity, straightness, and surface roughness. The reasons for these problems, which often result in quality short comings, are an alignment of the BTA drilling system and the unbalance of cutting force by work piece and tool shape. This paper analyzes the properties through an experiment which com¬pared single-edge BTA drills with multiple-edge BTA drills, as well as the shapes of the tools to cause an unbalance of cutting force, and its effect on the precision of the worked hole. Conclusions are as follows. 1) In SMSSC drilling, 60m/min of BTA with single and multi-edged tools proved the best cutting condition and the lowest wear character. 2) The roundness got a little worse as cutting speed was increased, but surface roughness was hot affected. 3) It was proved that the burnishing torque of both drills approached 26%. which is almost the same as the 24% insisted on by Griffiths, and the dispersion characteristic of the multi-edged BTA drill proved better than the single-edge BTA drill.

• 한국추진공학회지
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• 제21권1호
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• pp.44-50
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• 2017

지상고정장치는 발사체 엔진의 추력이 정상상태에 도달할 때까지 발사체를 발사대에 고정시켜주는 역할을 한다. 본 연구에서는 지상고정장치에 적용되는 구동 유압실린더의 형상 및 운동 특성에 대한 해석적 연구를 수행하였다. 유압 실린더의 수축 운동은 분리 동작에 가장 중요한 요소로서, 해석 결과 실린더의 slit 면적이 축소되고 초기 충전 압력이 증가될수록 수축 하중이 증가함을 확인하였다. 이를 통해 최적화된 slit 면적과 초기 충전압력을 결정하였다. Transient 해석을 통해 실린더가 수축 시 발생하는 하중, 변위, 내부 압력분포를 확인하였다. 해석 결과 실린더가 발생시키는 하중은 실린더에 작용하는 외력과 동일한 값을 발생시키는 것을 확인하였다. 또한 실린더가 운동하는 중에 실린더 내부의 압력분포는 일정한 것을 확인할 수 있었다.

• 한국자기학회지
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• 제22권3호
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• pp.79-84
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• 2012

나노크기의 물질이 가지는 새로운 특성을 응용하는 연구가 매우 활발하게 진행되어 지고 있다. 본 연구에서는 PAD법으로 제조한 ${\alpha}$-Fe 나노분말을 이용하여 높은 포화자화와 기계적인 경도, 화학적 안정성, 작은 입자로 인한 tape noise의 감소 등의 특성을 지니고 있는 질화철인 $Fe_4N$을 합성하고, 이를 환원/확산법과 $N_2$가스 질화법으로 합성한 $Fe_{17}Sm_2N_x$ 자성분말과 자성 특성을 비교하였다. $NH_3+H_2$(부피비 3 : 1) 혼합가스를 이용하였을 경우 $Fe_4N$의 생성 온도와 반응시간 등의 조건 변수를 통해 $400^{\circ}C$에서 4시간 동안 열처리함으로서 단일상의 $Fe_4N$이 생성되는 것을 관찰 할 수 있었으며, 나노크기의 $Fe_4N$ 분말과 마이크론 크기의 $Fe_{17}Sm_2N_x$ 분말의 포화자화의 값은 각각 149, 117 emu/g의 값을 나타내었다.

• International Journal of Korean Welding Society
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• 제5권1호
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• pp.15-28
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• 2005

The ball shear test was investigated in terms of the effects of test parameters, i.e., shear height and shear speed, with an experimental and non-linear finite element analysis for evaluating the solder joint integrity of area array packages. Two representative Pb-free solder compositions were examined in this work: Sn-3.5Ag-0.75Cu and In-48Sn. The substrate was a common SMD type with solder bond pad openings of 460 $\mu$m in diameter. The microstructural investigations were carried out using SEM, and the IMCs were identified with EDS. Shear tests were conducted with the two varying test parameters. It could be observed that increasing shear height, at fixed shear speed, has the effect of decreasing shear force for both Sn-3.5Ag-0.75Cu and In-48Sn solder joints, while the shear force increased with increasing shear speed at fixed shear height. Too high shear height could cause some undesirable effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball. The low shear height conditions were favorable for screening the type of brittle interfacial fractures or the degraded layers in the interfaces. The shear speed conditions were discussed with the stress analyses of the solder ball, and we cannot find any conspicuous finding which is related to optimum shear speed from the stress analyses.

• Transactions on Electrical and Electronic Materials
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• 제12권2호
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• pp.56-59
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• 2011

The characterization of the chemical mechanical polishing (CMP) process for undensified phophosilicate glass (PSG) film is reported using design of experiments (DOE). DOE has been used by experimenters to understand the relationship between the input variables and responses of interest in a simple and efficient way, and it typically is beneficial for determining the appropriatesize of experiments with multiple process variables and making statistical inferences for the responses of interest. The equipment controllable parameters used to operate the machine consist of the down force of the wafer carrier, pressure on the back side wafer, table and spindle speeds (SS), slurry flow (SF) rate, pad condition, etc. None of these are independent ofeach other and, thus, the interaction between the parameters also needs to be understoodfor improved process characterization in CMP. In this study, we selected the five controllable equipment parameters the most recommendedby process engineers, viz. the down force (DF), back pressure (BP), table speed (TS), SS, and SF, for the characterization of the CMP process with respect to the material removal rate and film uniformity in percentage terms. The polished material is undensified PSG which is widely used for the plananization of multi-layered metal interconnects. By statistical modeling and the analysis of the metrology data acquired from a series of $2^{5-1}$ fractional factorial designs with two center points, we showed that the DF, BP and TS have the greatest effect on both the removal rate and film uniformity, as expected. It is revealed that the film uniformity of the polished PSG film contains two and three-way interactions. Therefore, one can easily infer that process control based on a better understanding of the process is the key to success in current semiconductor manufacturing, in which the size of the wafer is approaching 300 mm and is scheduled to continuously increase up to 450 mm in or slightly after 2012.

• 한국산학기술학회논문지
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• 제11권4호
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• pp.1210-1215
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• 2010

프로브 카드는 반도체 제조 공정 전에 반도체 소자 및 필름의 기능과 성능을 검사하기 위한 테스트 장비이다. 반도체 산업의 급속한 기술 발전과 반도체 소자의 고집적화로 인하여 반도체 소자의 패드 간격과 패드의 수가 증가하고 있다. 따라서 반도체 소자의 크기 및 배열의 형태가 계속 축소됨에 따라 미세 피치를 갖고 검사용 핀의 수가 많은 프로브 카드가 필요하다. 본 논문에서는 수직형 프로브 카드의 적용을 위하여 MEMS 기술을 이용한 프로브 팁을 개발하였다. 프로브 팁의 설계를 위해서 유한요소해석을 이용하여 프로브 팁의 구조 및 기계적 특성에 대한 구조설계를 수행하였다. 또한 구조 설계를 적용한 프로브 팁을 제작하여 유한요소해석의 결과와 실제 시험을 통한 접촉력의 평가를 수행하였다. 이에 따라 피치 간격이 약 $50{\mu}m$이하의 프로브 카드를 제작하였다.

• 한국소음진동공학회논문집
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• 제22권9호
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• pp.853-860
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• 2012

This paper identifies a cause of pick up noise in a laser printer and a relationship between pick up noise and major components related to pick up noise. A pick up sound is affected by many components such as spring force, spring constant, and friction coefficient. Objective evaluation for the pick up sound is difficult because of back ground sound such as operating sound. Especially, a sound between a friction pad and a paper in the process of printing has become an essential issue in an aspect of quality evaluation. However the existing criteria for determining the above sound have solely relied on human's subjective judgments; which highlights the requirement to objectify these criteria. In this paper, the standard of existing pick up noise is established by finding the tonality, which is a psychoacoustic parameter, of noticeable limit sound level. Based on the findings of the method, the study has found factors which cause pick up noise and suggests the substitution of following components of printers such as spring constants, spring force, and the quality of friction pads. As a result, it is confirmed that the proposed pick up noise index has usefulness to classify whether existence of pick up noise with an objective evaluation and not to occur the noise based on design optimized combination of laser printer components.

• Design & Manufacturing
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• 제11권2호
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• pp.37-41
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• 2017

With light vehicle weight gradually becoming ever more importance due to tightened exhaust gas regulations, hot-stamping processing using boron alloyed steel is being applied more and more by major automobile OEMs since process assures both moldability and a high strength of 1.5 GPa. Although laser trimming is generally applied to the post-processing of the hot-stamped process with high strength, there have been many studies of in-die hot trimming using shear dies during the quenching of material in order to shorten processing times. As such, this study investigated the effects of the Shear rate and Shear mechanism on shear processes during the quenching process of hot-stamping material. In case of pad variable, padding force is very weak compared with shear force, so it does not affect the shear surface. In case of shear rate, the higher the shear at high temperatures and the higher the friction effect. As a result the rollover and the fracture distribution decreased, and the burnish distribution increased. Therefore, it is considered that the shear quality is guaranteed when high shear rate is applied in high temperature shear process.

• 한국전문물리치료학회지
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• 제28권2호
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• pp.154-160
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• 2021

Background: Theoretically, balance is affected by the height of center of mass (COM) during quiet standing. However, no one examined this in humans with variables derived from the center of pressure (COP). Objects: We have conducted balance experiment to measure COP data during quiet standing, in order to examine how the COP measures were affected by the height of COM, vision, floor conditions, and gender. Methods: Twenty individuals stood still with feet together and arms at sides for 30 seconds on a force plate. Trials were acquired with three COM heights: 1% increased or decreased, and not changed, with two vision conditions: eyes closed (EC) and eyes open (EO), and with two floor conditions: unstable (foam pad) and stable (force plate) floor. Outcome variables included the mean distance, root mean square distance, total excursion, mean velocity, and 95% confidence circle area. Results: All outcome variables were associated with the COM height (p < 0.0005), vision (p < 0.0005), and floor condition (p < 0.003). The mean velocity and 95% confidence circle area were 5.7% and 21.8% greater, respectively, in raised COM than in lowered COM (24.6 versus 23.2 mm/s; 1,013.4 versus 832.3 mm²). However, there were no interactions between the COM height and vision condition (p > 0.096), and between the COM height and floor condition (p > 0.183) for all outcome variables. Furthermore, there was no gender difference in all outcome variables (p > 0.186). Conclusion: Balance was affected by the change of COM height induced by a weight belt in human. However, the effect was not affected by vision or floor condition. Our results should inform the design of balance exercise program to improve the outcome of the balance training.

• 문화기술의 융합
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• 제8권3호
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• pp.265-270
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• 2022

본 연구는 콘크리트 궤도용 탄성레일체결장치(System 300-1)의 손상취약부에 관한 실험 및 해석적 연구이다. 콘크리트 궤도에서 탄성레일체결장치는 열차주행 시 레일과 침목을 결속하는 핵심 궤도구성품이다. 레일체결장치 구성품 중 방진패드와 텐션 클램프(Tension Clamp)는 압축력과 부상력에 대응하며 상시 변형이 발생되는 피로부재이다. 본 연구에서는 동일구간의 운행선에서 6년, 11년, 16년 동안 사용된 탄성레일체결장치를 채취하여 사용년수에 따른 텐션 클램프의 잔류변형 특성을 분석하였다. 또한 수치해석을 바탕으로 주요 구성품별 거동메커니즘을 분석하고 손상취약부를 도출하였다. 본 연구에서 수행한 수치해석을 통해 체결력 도입부터 외력 작용에 따른 텐션 클램프 각부의 응력(변형율)을 분석하여 텐션 클램프의 손상취약부를 도출하였다.