유한요소법을 이용한 다층 박막의 잔류응력분포 예측

최현창(Hyeon Chang Choi),박준협(Jun Hyub Park) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3

The mean stresses of the single and multi-stacked film are experimentally investigated. After stacking several layers on a wafer, we measure the curvature on the wafer. Followed by peeling each layer stacked, we measure the curvature on the wafer, again. Mean residual stresses are calculated from radiuses of the curvatures using the Stoney's equation. Microcantilever beams is constructed by removing substrate and the deflection at the end of a beam is measured. Finite element method for determining residual stress distribution in multi-stacked films with a multi-step doping process is studied for use in micromachining applications. We propose a finite element program for residual stress analysis (RESA) in multi-stacked polysilicon film. The distribution of residual stress field in multi-stacked films is predicted using RESA. And it is established for the prediction method determining the deflection in a cantilever beam using finite element method(FEM).

1차 크리프 속도를 고려한 크리프 균열 진전의 유한요소 해석

최현창,Choi, Hyeon-Chang 대한기계학회 1999 大韓機械學會論文集A Vol.23 No.7

An elastic-viscoplastic finite element analysis is performed to investigate detailed growth behavior of creep cracks and the numerical results are compared with experimental results. In Cr-Mo steel stress fields obtained from the crack growth method by mesh translation were compared with both cases that the secondary creep rate is only used as creep material property and the primary creep rate is included. Analytical stress fields, Riedel-Rice(RR) field, Hart-Hui-Riedel(HR) field and Prime(named in here) field, and the results obtained by numerical method were evaluated in details. Time vs. stress at crack tip was showed and crack tip stress fields were plotted. These results were compared with analytical stress fields. There is no difference of stress distribution at remote region between the case of 1st creep rate+2nd creep rate and the case of 2nd creep rate only. In case of slow velocity of crack growth, the effect of 1st creep rate is larger than the one of fast crack growth rate. Stress fields at crack tip region we, in order, Prime field, HR field and RR field from crack tip.

Ansys와 LabView를 이용한 프레스 성형용 파이프 인서트 주조금형 개발

노태정(Lho, Tae-Jung),최현창(Choi, Hyeon-Chang) 한국산학기술학회 2009 한국산학기술학회논문지 Vol.10 No.12

종래에는 신발 부품 등을 제작하는데 주조금형을 가열, 냉각하는 별도의 가열판과 냉각판을 사용해 왔다. 그러나 이것은 금형을 가열 및 냉각하는데 시간이 너무 오래 걸리는 단점이 있었다. 따라서 본 연구에서는 기존의 가 열판과 냉각판을 사용하던 방법을 대체하여 파이프 인서트 주조 금형을 사용한 신발창의 프레스 성형에 대한 적용 가능성을 제안하였다. 유한요소법을 사용한 수치해석이 금형의 온도분포 해석에 적용되었으며, 또한 LabView에 의해 그 온도를 실제로 측정하였다. 프레스 성형용 파이프 인서트 주조금형에 의해 부품을 제작하는 공정은 특히 생산성 면에서 아주 효과적이라고 검증되었다. Heating and cooling plate are separately used for heating and cooling cast dies for footwear parts. However, this has a disadvantage that it takes a long time to manufacture footwear parts etc.. In the present study, the pipe-inserted cast die for press forming process was proposed to substitute heating and cooling plate. The temperature distribution on the pipe-inserted cast die was analyzed by numerical work using a FEM. And its temperature was measured by LabView. A manufacturing by the pipe-inserted cast die for press forming process was effectively verified, especially in a productivity.

컴퓨터 그래픽 모델을 이용한 족부 관절의 생체역학적 해석

서민좌,김시열,조원학,최현창,최현기,Seo Min Jwa,Kim Si Yeol,Cho Won Hak,Choi Hyeon-Chang,Choi Hyeonki 대한의용생체공학회 2003 의공학회지 Vol.24 No.6

본 연구의 목적은 컴퓨터 그래픽 모델을 사용하여 보행 시 족부 관절의 기구학적 특성을 알아보는 것이었다. 모델에서 모든 관전은 단일중심(monocentric), 1 자유도 힌지 관절로 구성되었다. 보행 시 족부의 모션데이터는 4대의 카메라를 사용한 모션측정기로 얻었으며, 이 모션데이터를 피험자의 밭의 크기에 맞게 스케일링된 모델에 입력하여 시뮬레이션을 수행하였다. 첫 번째 발목발허리관절(tarsometatarsal joint)의 운동 범위(range of motion)는 $-8^{\circ}\;\~\;-13^{\circ}$ 이었으며, 발허리발가락관절(metatarsophanlangeal joint)에서의 운동범위는 $-13^{\circ}\;\~\;-48^{\circ}$ 이었다. 발목발허리관절과 발허리발가락관절에서의 기구학적인 데이터는 이전 연구와 비교했을 때 비슷한 경향을 나타내었다. 따라서 본 연구에서 제시하는 컴퓨터 그래픽을 기반으로 한 족부 모델링은 족부 관절의 생체역학적 해석을 위한 유용한 방법이라 할 수 있을 것이다. The purpose of this investigation was to study the kinematics of joints between the foot segments based on computer graphic model during the stance? phase of walking. In the model, all joints were assumed to act as monocentric. single degree of freedom hinge joints. The motion of foot was captured by a video collection system using four cameras. The model fitted in an individual subject was simulated with this motion data. The range of motion of the first tarsometatarsal joint was $-8^{\circ}\;\~\;-13^{\circ}$, and the first metatarsophanlangeal joint was $-13^{\circ}\;\~\;-48^{\circ}$. The kinematic data of tarsometatarsal joint and metatarsophanlangeal joint were similar to the previous data. Therefore, our method based on the graphical computer model is considered useful.

열응력과 잔류응력 하의 다층박막의 응력 해석

박준협(Jun-Hyub Park),최현창(Hyeon-Chang Choi) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8

Reliability problem in inkjet printhead, one of MEMS, is also very important. To eject an ink drop, temperature of heater must be high so that ink contacting with surface reaches above 280℃ on the instant. Its heater is embedded in the thin multi-layer in which several materials are deposited. MEMS processes are the main sources of residual stresses development. Residual stress is one of the factors reducing the reliability of MEMS devices. We measure residual stresses of single layers that consist of multiplayer. FE analysis is performed using design of experiment(DOE). Transient analysis for heat transfer is performed to get a temperature distribution. And then static analysis is performed with the temperature distribution obtained by heat transfer analysis and the measured residual stresses to get a stress distribution in the structure. Although the residual stress is bigger than thermal stress, thermal stress is more influential on fatigue life.

비접촉 평판 디스플레이 이송장치에서 양력을 고려한 평판 디스플레이의 처짐 해석

황성현(Sung Hyen Hwang),최현창(Hyeon Chang Choi),노태정(Te Jung Lho),손태영(Te Yong Son),박범석(Bum Suk Park) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.5

Flat Panel Display(FPD) is widely used a video display terminals to consumer products of LCD and PDP. The contamination and damage were affected by using the previous contact conveyor's method. In this paper, it analyzes the FPD deflection to develop the non-contact FPD transfer process using lift force. Each conveyor's equipment is called a horizontal conveyor, vertical conveyor and robot pick-up equipment. As result of an analysis of FPD panel's deflection, a robot pick-up equipment has performed according to under the present conditions like panel's weight and loaded glass to move FPD panel from one place to other places properly. Results of the analysis showed 0.474 ㎜, 0.424 ㎜ and 1.237 ㎜. Those values are lower than a predicted optimum values : 2 ㎜ for both horizontal and vertical conveyers; 5 ㎜ for robot pick-up equipment. Therefore, those results verify each equipment have safety and reliability.

수치 해석 방법을 이용한 크리프 균열 진전에 미치는 1차 크리프 속도의 영향 평가 : 1차 크리프 속도를 고려한 크리프 균열 진전의 유한요소

최현창 동명정보대학교 1999 東明情報大學校論文集 Vol.2 No.-

An elastic-viscoplastic finite element analysis is performed to investigate detailed growth behavior of creep cracks and the numerical results are compared with experimental results. In Cr-Mo steel stress fields obtained from the crack growth method by mesh translation were compared with both cases the secondary creep rate is only used as creep material property and the primary creep rate is included. Analytical stress fields, Riedel-Rice(RR) field, Hart-Hui-Riedel(HR) field and Prime(named in here) field, and the results obtained by numerical method were evaluated in details. Time vs. Stress at crack tip was showed and crack tip stress fields were plotted. These results were compared with analytical stress fields. There is no difference of stress distribution at remote region between the case of 1st creep rate + 2nd creep rate and the case of 2nd creep rate only. In case of slow velocity of crack growth, the effect of 1st creep rate is larger than the one of fast crack growth rate. Stress fields at crack tip region are, in order, Prime field, HR field and RR field from crack tip.

DEVELOPMENT OF A PROGRAM FOR PREDICTING RESIDUAL STRESS DISTRIBUTIIN IN MULTI-STACKED FILM

Choi, Hyeon Chang,Park, Yong Soo 동명정보대학교 2002 저널 정보공학기술 Vol.1 No.-

The mean stresses of the single and multi-stacked film are experimentally investigated. After stacking several layers on a wafer, we measure the curvature on the wafer. Followed by peeling each layer stacked, we measure the curvature on the wafer, again. Mean residual stresses are calculated from radiuses of the curvatures using the Stoney's equation[1]. Microcantilever beams is constructed by removing substrate and the deflection at the end of a beam is measured. Finite element method for determining residual stress distribution in multi-stacked films with a multi-step doping process is studied for use in micromachining applications. We propose a finite element program for residual stress analysis(RESA) in multi-stacked polysilicon film. The distribution of residual stress field in multi-stacked films is predicted using RESA. And it is established for the prediction method determining the deflection in a cantilever beam using finite element method(FEM).