열 및 압력 하중을 받는 소형 열 교환기에 대한 육면체요소와 사면체 요소의 사용에 따른 해석 결과 비교

명만식(Man-Sik Myung),유봉(Bong Yoo),김윤재(Yun-Jae Kim) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.10월

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.

T 분기관의 강화형상에 따른 소성한계하중에 대한 평가

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.

원형 노치 인장 시편의 완전 소성 해석

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 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.

LCD 패널의 응력 해석을 통한 단순화 칩핑 허용균열 길이 예측

김주희,명만식 대한기계학회 2019 大韓機械學會論文集A Vol.43 No.12

In this study, we assessed the effect of chipping generated in the process of cutting of an LCD panel and the effect of abrasives used to remove such chipping. For this, stress changes of 9- and 4-inch wide LCD panels with external weights were measured for defects; further, ground and non-defective LCD panels were also assessed. From the results, the chipping on the LCD panel was observed to increase stress locally and weaken the hardness, but the grinding for removal of chipping relieved the concentration of stress, similar to that of the non-defective panel. LCD 패널 제작과정에서 다양한 칩핑이 발생한다. 이는 초기 균열의 형태로 패널의 내구성에 영향을 미칠 수 있다. 본 연구에서는 칩핑이 LCD 패널의 내구성에 미치는 영향을 확인하고 칩핑 제거를 위해 수행되는 연마가공의 효과를 확인하였다. 이를 위해 외부 하중에 대한 9인치와 4인치 LCD 패널의 응력 변화를 연마 가공된 LCD 패널과 가공되지 않은 패널에서 비교하였다. 결과적으로 LCD 패널에 발생한 칩핑은 국부 응력집중 현상으로 인해 내구성이 약화되는 것을 확인하였다. 칩핑 제거를 위한 연마 작업은 손상이 없는 패널과 같이 응력집중 현상이 완화되는 것을 확인하였다.

완전소성해석을 이용한 원형노치 인장시편의 한계하중 및 완전소성응력장 해석

오창균,김윤재,박진무,명만식 대한기계학회 2005 大韓機械學會論文集A Vol.29 No.12

차량 기동을 고려한 도로 측구 맨홀 덮개의 한계 하중에 관한 연구

제두호,김주희,유삼현,명만식 육군사관학교 화랑대연구소 2014 한국군사학논집 Vol.70 No.1

In this paper, FE analysis was used to simulate the effects of loads of MOVs(Military Owned Vehicles) on the true stress-strain curves to a manhole cover. The research was carried out with a three-dimensional (3-D) rectangular geometry of manhole cover. To simulate the loads and its effect to manhole cover, we used the FEM(Finite Element Method). As a loading conditions, the distributed loads were considered, which were 10, 15, 20, 24 tons. Also, directions of tire were contemplated (e.g. longitudinal and horizontal directions). As the loads below 20 ton were applied, the manhole deformed in the elastic region, and when the loads were removed, the form of manhole was returned to original state. However, the loads above the 20 ton were applied, the material was transformed as a plastic deformation. Moreover, we found that the materials would occur the plastic collapse when the loads about 35 ~ 38 ton were applied. The results of present study can be used to predict the effect of loads of MOVs to manhole during maneuvering on the roads.

클러치 스냅링부 파괴 예측을 위한 구조응력기법 연구

김주희(Ju Hee Kim),명만식(Man Sik Myeong),오창식(Chang Sik Oh),김윤재(Yun Jae Kim) 대한기계학회 2016 大韓機械學會論文集A Vol.40 No.2

복잡한 기계장치에 대한 내구신뢰성 평가는 단순한 응력해석을 통해 피로수명을 예측하는 것이 일반적인 방법이다. 하지만 기존 방법은 유한요소 해석 시 여러 가지 요인에 의해 일관된 응력해석 결과를 얻기 어려워 해석자에 따라 상이한 수명을 예측하는 단점을 지닌다. 하지만 구조응력을 기반으로 하는 내구신뢰성 평가 기법은 이러한 단점을 보완하여 보다 합리적인 결과를 제공해 준다. 구조응력기법은 유한요소 모델의 요소 수와 요소 형태에 무관하게 일관된 응력결과를 제공하기 때문에 신뢰성이 높은 내구도 평가 결과를 얻을 수 있다. 해석조건 및 환경에 독립적인 결과를 제공해 주는 구조응력은 최근 대형선박 설계 및 각종 기계장치의 피로수명 예측에 종종 활용되고 있어 보다 깊이 있고 체계적인 연구가 필요하다. 따라서, 본 연구에서는 (a) 유한요소모델의 형태에 상관없이 요소에 독립적인 구조응력 산출기법을 제시하고, (b) 이를 이용하여 자동차 클러치 스냅링부의 구조응력 산출하여 피로파괴를 예측하고자 한다. The endurance reliability assessment of a highly complex mechanism is generally predicted by the fatigue life based on simple stress analysis. This study discusses various fatigue life assessment techniques for an automobile clutch snap ring. Finite element analyses were conducted to determine the structural stress on the snap ring. Structural stress that is insensitive in regards to the mesh size and type definition is presented in this study. The structural stress definition is consistent with elementary structural mechanics theory and provides an effective measure of a stress state that pertains to fatigue behavior of welded joints in the form of both membrane and bending components. Numerical procedures for both solid models and shell or plate element models are presented to demonstrate the mesh-size insensitivity when extracting the structural stress parameters. Conventional finite element models can be used with the structural stress calculations as a post-processing procedure. The two major implications from this research were: (a) structural stresses pertaining to fatigue behavior can be consistently calculated in a mesh-insensitive manner regardless of the types of finite element models; and (b) by comparing with the clutch snap-ring fatigue test data, we should predict the fatigue fractures of an automobile clutch snap ring using this method.

클러치 스냅링부 형상 설계를 위한 구조응력 민감도 해석

김주희(Ju Hee Kim),명만식(Man Sik Myeong) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.3

수만개의 부품으로 만들어진 자동차는 그 구조와 기능이 매우 복잡하고 다양하다. 특히 엔진은 자동차의 성능과 수명을 결정하는 핵심적인 구성품이며, 이 중 클러치는 자동차의 동력을 전달하는 중요한 부품 중 하나이다. 클러치 스냅링부는 엔진의 구동력을 바퀴로 전달하는데 필요한 구동력을 차단 및 연결하는 부품으로 많은 반복하중에 노출되어 엔진의 수명을 결정하는 주요 구성품이다. 본 논문에서는 유한요소해석법을 이용하여 클러치 스냅링부의 구조응력을 계산하고 피로수명평가를 위한 실험결과를 바탕으로 클러치 스냅링부의 형상설계 최적화 과정을 제시하고자 한다. 이를 위해 클러치 스냅링부의 주요 형상의 설계인자를 결정하여 형상변화에 따른 구조응력 변화를 통해 피로수명을 예측하였다. Automobiles are made up of tens of thousands of components, which are complicated and varied in their structure and functions. Especially, the engine is a very important component in determining the performances and functions of the automobile. One of these performances and functions, the clutch snap-ring, is the component of the clutch to transmit and cut off the power from the engine to the transmission process. Moreover, this component determines the life of the engine because of its exposure to cyclic loading. In this study, finite element analysis was conducted to determine the structural stress on the snap-ring, and we proposed a procedure for the geometry design of the optimization based on the experimental results of the fatigue life. To do this, we selected the main design parameters of the clutch snap-ring, and predicted the fatigue life consequences of the change of structural stress as the change of the geometry of the clutch snap-ring.