• 한국정밀공학회지
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• 제22권2호
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• pp.133-138
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• 2005

The deformation of sheet metal due to the residual stress during blanking or piercing process, is numerically simulated by means of a commercial finite element code. Two dimensional plain strain problem is solved and then its result is applied to the deformation analysis of the lead frame. The plain strain element is applied to the 2D problem to observe the Von Mises equivalent stress concentration at the both shearing edges. As the punch penetrates into the sheet material, the stress concentration generated on both edges is getting increased to be the shearing surface. The limits of the punching depth applied to the simulation is 16% and 24% of the sheet thickness for the plain strain element and the hexahedral element, respectively. The hexahedral element and the limit of punching depth were applied to the deformation analysis of the lead frame for the blanking process. The FEM results for the lead deformation were very good agreement with the experimental ones. This paper shows that the coarse mesh has enabled to analyze the lead deformation generated due to the blanking mechanism. This simple approach to save the calculation time will be very effective to the design of the blanking tools in industries.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.389-394
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• 2003

In this paper, a shape optimization technique is applied to design of an air-conditioner mounting bracket. The mounting bracket is a structural component of an engine, on which bolts attach an air-conditioner compressor. The air-conditioner mounting bracket has a large portion of weight among the engine components. To reduce weight of the bracket, the shape is optimized using a finite element software. The compressor assembly, composed of a compressor and a bracket is modeled using finite elements. An objective function for the shape optimization of the bracket is the weight of the bracket. Two design constraints on the bracket are the first resonant frequency of the compressor assembly and the fatigue life of the bracket. The design variables are the shape of the bracket including thickness profiles of the front and back surfaces of the bracket, radius of outer bolt-holes, and side edge profiles. The coordinates of the FE nodes control the shape parameters. Optimal shapes of the bracket are obtained by using SOL200 of MSC/NASTRAN.

• 대한조선학회논문집
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• 제43권2호
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• pp.206-212
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• 2006

Structural reliability of electrical panels installed in naval vessels is of critical importance from structural performance viewpoint. The electrical panels may be exposed to vibration and fatigue loadings from internal and external sources as well as wave loadings which result into a crack and fracture due to the decrease of fatigue strength. It is also well known that welded joints including brackets within steel structures .such as vessels and bridges are vulnerable against such repeated loadings. This study introduces a preliminary result of the optimized shape of frame bracket consisting of electrical panels in navel vessels against fatigue loading and their fatigue life at brackets of electrical panels by means of hot spot stress and structural stress methods.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2010년도 정기 학술대회
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• pp.409-412
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• 2010

본 연구는 목조 건축물 흙벽의 수평가력실험 결과를 이용한 내진성능 평가를 목적으로 한다. 흙벽 실험시험체는 기둥과 보 결합방식에 따라 민도리, 초익공, 장여방식으로 분류되고 벽체 형태에 따라 창문, 문, 전면 벽체, 인방 부재수 등으로 계획을 하였다. 12개 흙벽 시험체의 가력결과, 전면 벽체 시험체는 변위각 1/30에서 가장 큰 강성 저하율을 보이며 중인방과 수직재가 있는 벽체는 에너지 소산능력이 가장 큰 것으로 나타났다. 기존 연구로부터 목조 건축물 항복점 평가방법을 이용하여 등가탄소성 곡선으로 나타낸 전단내력은 민도리방식이 프레임과 전면 벽체일 경우 가장 크고, 전단응력은 벽체 개구율에 따라 다르게 나타났다. 실험결과로부터 적용 대상 건축물의 X, Y방향 구조성능을 산출하고 구조내진지표와 역량스펙트럼을 이용하여 내진성능 평가를 실시한 결과, 대상 목조 건축물은 내진성이 있음으로 평가되었다.

• 한국구조물진단유지관리공학회 논문집
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• 제22권1호
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• pp.176-182
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• 2018

본 연구의 목적은 볼접합부를 갖는 원형강관의 좌굴실험 결과를 토대로 하여 국내외 압축재 설계규준과 비교 평가함으로써 부재의 좌굴내력 및 좌굴길이 계수의 안전성과 합리성을 조사하는 것이다. 좌굴성능 평가를 위해 선정된 원형강관은 Ø$48.6{\times}2.8t$와 Ø$60.5{\times}3.2t$ 및 Ø$76.3{\times}3.2t$이다. 국내외 압축재 설계를 위해 우리나라의 하중저항계수 설계법(LRFD), 일본의 한계상태 설계법(LSD) 및 영국의 BS5950 규준을 적용하였다. 본 연구에서는 선행연구의 실험결과와 국내외 설계규준과의 좌굴성능을 비교 분석하였다. 그 결과를 요약해 보면 다음과 같다. 각국의 압축재 설계규준에서 부재의 전체길이를 좌굴길이로 적용한 결과 실험에 의한 좌굴내력의 64%~89% 정도로 나타났다. 따라서 안전을 위해 현재 설계 규준식에 준하여 부재설계를 수행하는 것이 바람직하다고 판단되었다. 실험결과 측정된 좌굴내력은 우리나라, 일본 및 영국의 압축재 설계규준에서 좌굴길이를 순수 원형강관만으로 고려한 좌굴내력 값에 비해 1.02배~1.43배 높은 것으로 나타났다. 따라서 스페이스 프레임 구조물 설계에 있어 개별부재 좌굴내력은 절점 간 길이가 아닌 순수 원형강관의 길이로 좌굴계수를 고려할 필요가 있을 것으로 보여 진다.

• 대한기계학회논문집A
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• 제31권11호
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• pp.1083-1092
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• 2007

The objective of the present paper is to evaluate the effect of the evolution of contact surface profile caused by fretting wear on fatigue life of press-fitted shaft by means of an analytical method based on experimental data. A finite element analysis was performed to analyze the stress states of press-fitted shaft, considering the worn contact profiles of shaft. The fatigue lives of the press-fitted shaft reflecting the evolution of contact stress induced by fretting wear were evaluated by stress-life approach using fatigue notch factor. It is found that the stress concentration of contact edge in press-fitted shaft decreases rapidly at the initial stage of total fatigue life, and its location shifts from the contact edge to the inside with increasing number of fatigue cycles. Thus the change of crack nucleation position in press-fitted shaft is mainly caused by the stress change of contact edge due to the evolution of contact surface profile by fretting wear. Furthermore, the estimated fatigue lives by stress-life approach at the end of running-in period of the fretting wear process corresponded well to the experimental results. It is thus suggested that the effect of fretting wear on fatigue life in press fits is strongly related to the evolution of surface profile at the initial stage of total fatigue life.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.277-282
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• 2011

Bogie frame is typical safety part of railway vehicle. Total serviceable life of bogie frame will be evaluated by Cumulative Damage Approach Method that is defined by dynamic strain measurement during revenue service under the actual track conditions. As a result of the standardization process developed in British Standard Institution, BS 7608 defines for fatigue design and test method of steel structure by fatigue test results over the long period. This paper evaluates the total serviceable life applying BS 7608 for the bogie frame of Electric Multiple Unit to verify structural safety of the bogie frame.

• 한국정밀공학회지
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• 제21권12호
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• pp.146-153
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• 2004

We compared the fatigue characteristics of weld metal with those of base metal, and not heat-treated with heat-treated. Also, we examined the influence of bead in a viewpoint of fatigue life. From the experimental results, it has been seen that the fatigue characteristics of welded specimens grinded the toe of bead are slightly better than not grinded. We have seen that the fatigue life is affected more by the stress concentration on the profile change in the weld toe rather than by residual stress influence, because heat-treated or not had almost no influence on the fatigue characteristics.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.830-835
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• 2007

In this paper, stress analyses using shell and solid elements on weld zone of railway bogie frame were performed. To calculate stress distribution on weld zone, a coupling model using shell and solid elements was suggested. For this purpose, we performed specimen analyses on T-type solid and shell model of T-type panels which were modeled using shell elements, solid elements and coupled elements, respectively. The result showed that the stress concentration at weld zone was occurred in solid model, but it didn't occur in shell model. And the stress distribution of coupled model was similar to that of solid model. Also, we applied the coupled modeling method on the analysis on weld zone of bogie frame. The stress distribution of coupled model showed much higher compared to that of shell only model. Therefore, the coupled model method is highly recommended for the stress analysis in weld zone of bogie frame.

• 마이크로전자및패키징학회지
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• 제14권2호
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• pp.49-57
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• 2007

본 연구에서는 Au 와 Sn을 rf-magnetron sputter를 이용하여 다층막(multilayer)과 동시증착(Co-sputter)방법으로 스퍼터링하여 기판위에 AuSn 솔더를 형성하였고, 솔더의 조성제어와 특성 분석을 통해 Sn rich AuSn 솔더의 형성 기술에 대하여 연구하였다. AuSn 솔더를 형성하기 앞서 Au와 Sn에 대하여 단일 금속 증착을 하였다. 이를 토대로 AuSn솔더를 증착하기 위한 실험 조건을 확보하였다. 증착변수로는 기판의 온도, rf 전력과 두께 비를 이용하였다. 다층막의 경우, 고온의 기판에서 솔더 합금의 표면거칠기와 조성이 보다 정확하게 제어되었다. 이에 비해 동시증착 솔더는 기판의 온도에 의한 조성의 변화가 거의 없었으나, rf전력에 의해서 조성이 보다 쉽게 제어할 수 있었다. 여기에 더해, 동시 증착 솔더 박막의 대부분은 증착동안에 금속간 화합물로 변화한 것을 알 수 있었다. 화합물의 종류는 XRD로 분석하였다. 형성된 솔더 박막을 플럭스를 이용하지 않고 리드프레임에 접합하여 접합강도를 측정하였다. 다층형의 경우 Au 10wt%의 조건에서 최대 $33(N/mm^2)$ 전단응력을 나타내었으며, 동시증착형은 Au 5wt%에서 $460(N/mm^2)$ 전단응력을 나타내었다.