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명만식(Man-Sik Myung),김윤재(Yun-Jae Kim),윤기봉(Ki-Bong Yoon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The present work provides effects of reinforcement shape and area on plastic limit loads of branch junctions, based on detailed three-dimensional finite element limit analysis and small strain FE limit analyses assuming elastic-perfectly plastic material behavior. Three types of loading are considered; internal pressure, in-plane bending on the branch pipe and in-plane bending on the run pipe. It is found that reinforcement is the most effective in the case when (in-plane/out-of-plane) bending is applied to the branch pipe. When bending is applied to the run pipe, reinforcement is less effective, compared to the case when bending is applied to the branch pipe. The reinforcement effect is the least effective for internal pressure.
RF MEMS Filter 설계를 위한 몰리브덴박막의 기계적 물성 측정
명만식(Man Sik Myung),김윤재(Yun-Jae Kim),좌성훈(Sung-Hoon Choa),이창승(Chang Seung Lee),박준협(Jun-Hyub Park) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
This paper presents a novel experimental method to investigate the strength of material, Mo, which is commonly used as an electrode in RF(radio frequency) microelectromechanical systems(MEMS) filter. An experimental method was developed to save time of set-up of specimen and easy to align. A non-contact position measuring system based on the principle of capacitance micrometry with 0.1nm resolution for displacement measurement was used to measure total displacement. And new specimen was designed and fabricated to easily manipulate, align and grip a thin-film for a tensile test. FE analysis for specimen was performed to calculate stress-strain curve from the measured load-displacement curve. The 2 kinds of widths were tested to investigate a size effect. The thickness of the thin film is 1.0μm and 2 kinds of width were tested to get mechanical properties.
자동차 경량화를 위한 텐션 링크의 최적 형상에 관한 연구
명만식(Man-Sik Myung),허영호(Yinghu Xu),최병익(byung-Ik Choi),이학주(Hak-Joo Lee),김주성(Joo-Sung Kim),김기주(Kee-Joo Kim),김윤재(Yun-Jae Kim),박준협(Jun-Hyub Park) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Due to the global environment problems and the consumer's need for higher fuel efficiency, it becomes very important for the global automotive industry to reduce the vehicle weight. The link component of chassis is applied by 6-DOFs (degree offreedom) loads and should withstand the loads for life cycle. The existed I-beam type link component may have a weak point for a special direction load. In present study, it was innovatively investigated to the optimal shape of link component that could withstand all directions loads and reduce the weight. The 3 type shapes were analyzed and the best optimized shape was found. The optimized design can reduce the weight by 40% of original link that made with steel. The environment and energy related problem has become one of the most important global issues in recent years. Accordingly there have been significant efforts on improving the fuel efficiency of automobiles. One of the most effective ways of improving the fuel efficiency of automobiles is the weight reduction. For example, a new generation six-passenger car is currently under development in the advanced countries and the targeted fuel efficiency is more than three times of the current level.
명만식(Man-Sik Myung),오창균(Chang-Kyun Oh),김윤재(Yun-Jae Kim),박진무(Jin-Moo Park) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
For the last four decades, tension test of notched bars has been performed to investigate the effect of stress triaxiality on ductile fracture. To quantify the effect of the notch radius on stress triaxiality, the shown that the Bridgman equation is not correct, possibly due to his assumption that stain is constant in the necked ligament. Up to present, no systematic work has been performed on fully plastic stress fields for notched bars in tension. This paper presents fully plastic results for tension of notched bars and plates in plane strain, via finite element limit analysis. The notch radius is systematically varied covering both un-cracked and cracked cases. Comparison of plastic limit loads with existing solutions shows that existing solutions are accurate for notched plates, but not for notched bars. Accordingly depth are also given, which again indicates that the Bridgman solution for notched bars is not correct and inaccuracy depends on the notch radius and depth.
RF MEMS switch 설계를 위한 Al-3 Ti 박막의 기계적 물성 측정
박준협(Jun-Hyub Park),명만식(Man Sik Myung),김윤재(Yun-Jae Kim),좌성훈(Sung-Hoon Choa),이창승(Chang Seung Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
This paper presents a novel experimental method to investigate the strength of material, Al-3 Ti, which is commonly used in RF(radio frequency) microelectromechanical systems(MEMS) switch. The experimental method involves the development of a new tensile loading system. A non-contact position measuring system based on the principle of capacitance micrometry with 0.1㎚ resolution for displacement measurement. And new specimen was designed and fabricated to easily manipulate, align and grip a thin-film for a tensile test. The material used in this study was Al-3 Ti thin film, which was used in RF switch. The thickness of the thin film is 1.1 m and 3 kinds of width were tested to get mechanical properties.
박준협(Jun-Hyub Park),명만식(Man Sik Myung),김윤재(Yun-Jae Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
This paper presents high cycle fatigue properties of an Al-3%Ti thin film, used in a RF (radio-frequency) MEMS switch for a mobile phone and also describes new test method for obtaining static and dynamic characteristics of thin film and reliability evaluation method on MEMS device with thin film developed by authors. Durability should be ensured for such devices under cycling load. Therefore, with the proposed specimen and test procedure, tensile and fatigue tests were performed to obtain mechanical and fatigue properties. The specimen was made with dimensions of 1000㎛ long, 1.0㎛ thickness, and 3 kinds of width, 50, 100 and 150㎛. High cycle fatigue tests for each width were also performed, from which the fatigue strength coefficient and the fatigue strength exponent were found to be 193㎫ and ?0.02319 for 50㎛, 181㎫ and ?0.02001 for 100㎛, and 164㎫ and ?0.01322 for 150㎛, respectively. We found that the narrower specimen is, the longer fatigue life of Al-3%Ti is and the wider specimen is, the more susceptible to stress level fatigue life of Al-3%Ti was.
이국희(Kuk-Hee Lee),명만식(Man-Sik Myung),김윤재(Yun-Jae Kim),박치용(Chi-Yong Park),이성호(Sung-Ho Lee),김태룡(Tae-Ryong Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
This paper presents plastic limit load solutions for branch junctions under in-plane bending applied to the run pipe, based on three-dimensional (3-D) FE limit analyses using elastic-perfectly plastic materials. To assure reliability of the FE limit loads, the effect of kinematic boundary conditions and the length of branch pipe on the FE limit loads are addressed. Then, based on the FE results, the limit load solutions are proposed for branch junctions under in-plane bending applied to the run pipe. The proposed solutions are valid for ratios of the branch-to-run pipe radius and thickness from 0.0 to 1.0, and the mean radius-to-thickness ratio of the run pipe from 5.0 to 20.0.
굽힘하중을 받는 분기관의 소성 붕괴 하중에 항복응력과 탄성계수의 비가 미치는 영향
정하주(Hajoo Chung),이국희(Kuk-Hee Lee),명만식(Man-Sik Myung),김윤재(Yun-Jae Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
This paper quantifies the effect of the yield strength-to-elastic modulus ratio on plastic collapse and instability loads for branch piping junctions under in-plane and out-of-plane bending. The finite element limit analyses based on elastic?perfectly-plastic materials using the large geometry change option provide plastic collapse loads (using the twice-elastic-slope method) and instability loads, and the plastic limit loads are determined from FE limit analyses using the small geometry change option. The plastic collapse loads and instability loads for branch pipe under bending are lower than limit loads. And the effect of internal pressure on plastic collapse and instability loads has been investigated. A wide range of parameters related to the bend geometry is considered.