Al 2024-T3合金의 表面微小龜裂 分布 特性과 殘存壽命評價法에 관한 硏究

안원기 동아대학교 1996 국내석사

Dy₂O₃, MnCO₃ 및 SiO₂가 첨가된 BaTiO₃계의 입자 성장 거동 및 유전 특성

안원기 경상국립대학교 대학원 2023 국내석사

제하 컴플라이언스법과 하중비 해석을 이용한 JR 곡선 및 Tmat의 평가

안원기 東亞大學校 敎育大學院 1999 국내석사

최근 화력발전 설비나 원자력 발전 설비를 구성하고 있는 재료들은 고온에서 장시간 가동되기 때문에 사용재료에 대한 안정성 확보가 중요하다. 이러한 재료들의 안정성 평가법으로는 ASTM E813 규정에 단일 시험편법(single specimen method)에 의한 제하 컴플라이언스법(unloading compliance method)과 복수 시험편법(multiple specimen method)이 규정되어 있으며, 많은 연구자들에 의해 여러 형태의 시편과 구조물의 재료 종류에 따른 파괴인성 평가법의 신뢰성이 수립되고 있으나, 후중-변위 곡선(load-displacement curve)과 균열 선단에서의 회전보정 및 소성변형을 고려한 균열길이의 산출로 물리적인 의미에 대한 배경이 부족하고 실제 적용 절차가 단순하지 않는 문제점을 가지고 있다. 그리고 파괴 저항 곡선(J-R curve) 평가지 Paris는 균열 성장의 안정과 불안정성을 평가할 수 있는 파라미터(parameter)로서 찢어짐 계수(tearing modulus, T_(mat))를 제안하였으나, 온도 변화에 따른 적용 가능성을 연구한 자료는 매우 부족한 실정이다. 따라서 본 연구에서는 파괴인성 평가시 재료의 소성변형에 의한 가공경화 효과를 바탕으로 단순 인장-변위 곡선을 이용하여 J-R곡선을 평가할 수 있는 하중비해석법(load ratio analysis method)을 도입하여 원자로 압력용기강으로 사용되고 있는 SA 508 C-3재의 사용 분위기(상온, 200℃,300℃)에 따라 제하 컴플라이언스법과 하중비 해석에 의한 J-R곡선을 비교, 평가하고, Paris가 제안한 T_(mat)의 불안정 파괴의 매개변수로서의 적용 가능성과 국부 파괴 변형률(local fracture strain)에 의한 이론적인 J_(IC)값을 위 두 실험치와 비교하여 다음과 같은 결론을 얻었다. 1. 제하컴플라이언스법에 의한 균열길이 측정시 초기에 균열길이 감소현상이 나타났고 이 현상은 반복 제하시 균열 선단부의 압축응력에 의한 것으로 생각되며 이 원인으로 인해 제하 컴플라이언스법의 J-R곡선이 하중비 해석에 비해 과대평가 되었다. 2. 각 온도에서 제하컴플라이언스법과 하중비 해석에 의한 J-R곡선의 지수근사식을 비교하면 하중비 해석에 의한 지수 근사식의 계소 C_(1), C_(2)는 상온에서 각각 12.69%, 12.54% 감소하였고, 200℃에서 19.11%, 11.81% 감소하였으며, 300℃의 경우 18.6%, 10.87% 감소하였다. 3. 상온의 경우 탄소성 파괴인성치(J_(IC)) 및 불안정 균열성장에 대한 저항력(T_(mat))이 가장 크게 나타났으며, 온도가 증가함에 따라 균열성장에 대한 구속력이 약화되어 J_(IC)값 및 T_(mat)값이 계속적으로 감소함으로서 찢어짐 계수가 불안정 파괴의 매개변수로서 적용 가능성이 있음을 알 수 있었다. 4. 인장실험으로 구한 국부파괴변형률(ε_(c))를 이용하여 이론식으로부터 탄소성 파괴 인성치(J_(IC))를 직접 구할 수 있었으며, 온도변화에 따라 실험적으로 구한 방법과 비교적 잘 일치함을 알 수 있었다. Safety and integrity are required for reactor pressure vessels because they are operated in high temperature. There are single specimen method, multiple specimen method, and load ratio analysis method which used as evaluation of safety and integrity for reactor pressure vessels. In this study, the fracture resistance curve(J-R curve), elastic-plastic fracture toughness (J_(IC)) and material tearing modulus (T_(mat)) of SA 508 class 3 alloy steel used as reactor pressure vessel steel are measured and evaluated at room temperature, 200℃ and 300℃ according to unloading compliance method and load ratio analysis method. And then the comparison with experimental J_(IC) and theoretical J_(IC) and theoretical J_(IC) by local fracture strain is managed. The main results were summarized as follows 1. The negative crack growth phenomenon has been shown in determining J_(IC) from unloading compliance method because of compressive residual stress caused by plastic zone size size of crack tip. So J-R curves by unloading compliance method are higher than those by load ratio analysis method at room temperature, 200℃ and 300℃. 2. Exponential fitting values, C_(1) C_(2) by load ratio analysis method decrease 12.69%, 12.54% respectively at room temperature, 19.11%, 11.81% respectively at 200℃ and 18.6%, 10.87% respectively at 300℃ than those by unloading compliance method. 3. It is observed that J_(IC) and T_(mat) values are highest at room temperature and as the temperature level increase they decrease proportionately. So tearing modulus has a applicability as crack instability parameter. 4. Elastic-plastic fracture toughness (J_(IC)) by theoretical equation of local fracture strain (ε_(c)) which can measured by using tensile test is slightly similar to experimental J_(IC).

A1 2024-T3 合金의 表面微小龜裂 分布特性과 殘存壽命評價法에 관한 硏究

안원기 東亞大學校 大學院 1996 국내석사

To assure the safety and reliability of a component, a life method has been developed. The method is based on the micro crack growth rate and the micro crack distribution. Plane bending fatigue tests were carried out on the plain specimen of Al 2024-T3 and the initiation and growth behavior of surface micro cracks were observed. And also, the ststistical distribution of surface length of multiple micro cracks and their maximum length were investigated. And the maximum surface crack length distributions were analyzed on the based of the statistics of extremes in order to examine the possibility of the fatigue life prediction. The main results obtained are summarized as follows ; 1. Both surface crack length and maximum surface crack length in Al 2024-T3 follow the three-parametic Weibull distribution and the variation of the maximum surface crack length distribution is greater than that of surface crack length distribution. 2. Surface crack density increases linearly with cycle ratio, N/N_(f). And as the elongation of materials becomes greater, crack density becomes more increased. From this results, it is thought that the plastic deformation of each material affects on crack density. 3. There is an relation of exponential function between surface crack length and. number of cycles, N. But, a linear relationship is observed between the logarithms of main surface crack length and the cycle ratio, N/N_(f). 4. The maximum crack length in an area larger than the sample area can be estimated with a help of the statistics of extremes. Therefore, the remaining life of a component may be accurately predicted by measuring the distribution of surface micro crack length in critical part.

로봇용 직류 서어보 모터 제어에 관한 연구

안원기 延世大學校 1988 국내석사

로봇 관절의 백래쉬 보상을 위한 외란관측기 설계

안원기 인하대학교 대학원 2007 국내석사

^(13)CO₂/^(12)CO₂ 동위원소비 측정용 광음향 검출감도 향상을 위한 검출기 최적화 연구

안원기 순천향대학교 일반대학원 2007 국내석사

적외선 분광기는 분산형과 비분산형으로 나누어지며, 이 중 비분산형 적외선 분광기는 목적하는 한 가지 성분에 대하여 높은 감도의 분석이 가능하다. 또한 비분산형 분광기는 구조가 비교적 간단하여 제조비용이 적고 조작이 간편하며, 크기가 작다는 이점을 가진다. 비분산형 적외선 분광기 중 광음향 효과를 이용한 광음향 분광기의 성능은 광변조장치와 온도조절장치 그리고 검출기에 영향을 받는다. 본 연구에서는 광음향 분광기의 각 부분 장치를 제작하였고, 특히 검출기의 최적 조건을 확인하고 제작한 마이크로폰 설치형 검출기의 성능을 상용 마이크로폰 설치형 검출기와 비교하고자 하였다. 제작한 광변조 장치는 10㎐에서 0.42‰의 구동 오차를 가지는 것을 확인하였고, 온도조절장치는 PAS 내의 ^(13)CO₂ 검출기의 온도를 46.7±0.3℃로 안정되었다. 또한 동위원소분석에 적합한 선택성이 높은 Lehrer-Luft형 검출기를 제작하였고, 검출 감도에 영향을 미치는 검출기 내의 CO₂ 조성을 변화시켰을 때 감응도와 교차 감응도를 확인하였다. 검출기 내 ^(13)CO₂ 농도가 증가함에 따라 시료 량에 대한 감응도가 증가하는 반면 교차 감응도 또한 증가하는 것을 확인하였고, 검출기 내 13CO2 농도가 감소함에 따라 시료 량 변화에 대한 감응변화량이 증가하는 것을 확인하였다. 검출기 내의 ^(13)CO₂의 농도가 증가함에 따라 시료 내 ^(13)CO₂ 선택도는 감소하고, 시료 량의 증가에 대해서는 검출기 내의 ^(13)CO₂ 농도가 낮을 때 선택도가 급격히 감소함을 확인하였다. 검출기 내의 기체 농도가 5%일 때 최적의 측정 조건을 만족함을 확인하였고, 상용 마이크로폰과 제작 마이크로폰을 검출기에 각각 설치하여 신호 재현성을 확인하였을 때 상용마이크로폰에 비하여 제작마이크로폰의 신호 재현성이 0.53‰로 더 안정적이었다. Determination of ^(13)CO₂/^(12)CO₂ isotope ratio is an important subject in many fields such as geology, environmental science, biology and medicine. IRMS(isotope ratio mass spectrometry) has been used as the principal method for measuring the ^(13)CO₂/^(12)CO₂ isotope ratio. IRMS generally provides high accuracy, but it is expensive and difficult to operate. Recently, PAS(photoacoustic spectrometry) is drawing attention as an alternative method for measuring the isotope ratio. In this work, we have made Lehrer-Luft type PAS detector, condenser microphone, chopper and thermo- controlling system in order to measure the ^(13)CO₂/^(12)CO₂ isotope ratio and optimized the concentration of ^(13)CO₂ and ^(12)CO₂ within a detector cell. The microphone designed as RFCM(radio frequency condenser microphone) and amplifying circuit of PA signal to microphone were made and assembled to complete the PAS detector. The microphone made in this research has been compared with the common microphone type PAS detector.

고등학교 『국사』과목 정기고사 문항유형의 분석과 개선방안

안 원기 경북대학교 교육대학원 2009 국내석사

The purpose of this study is to investigate how much the purposes of history education emphasized in the national curriculum or history education are realized in the regular examinations for high school students. The author in this study classified the items of the history subject exams that are regularly conducted for all high school students into types of the purposes of history education, identified their characteristics and problems, and presented how to improve the items in schools. The subjects of this study were the items in the midterm exam of the first term of 2008 for the six high schools located in Taegu. The definition and characteristics of educational estimation were established as a estimation method, and the items of six schools were classified by their types based on the estimation categories of history subject provided by the Korea Institute for Curriculum and Evaluation and the sub-categories of historical reasoning that is recently focused on. Meanwhile, the items were classified by the use of subject materials in their composition, and the characteristics of the items in schools were identified when compared to the recent History of Korea Exam with the level of high school students. According to the results of this study, items for asking knowledge of facts and conceptions were excessively shown but items for asking the estimation and attitudes on historical facts were rarely shown. Also, the analysis of the items based on historical reasoning revealed that items for asking reasoning were at sufficiently low rate. As for the review of the items by subject materials, the items by using of materials were of small number. In order to improve those problems, some suggestions may be presented as follows. First, educational purposes and estimation standards in which historical interpretation and reasoning are reestablished and items in which the several reestablished purposes are well-balanced should be provided. Second, items for measuring historical imagination that reveals the characteristics of history most, as subjective questions, and of utilizing various materials should be prepared.

DEVELOPMENT OF A DESIGN TOOL TO ASSIST LAYOUT : LAYUP DESIGN TO MINIMIZE WARPAGE OF A PWB DURING FABRICATION AND REFLOW SOLDER PROCESSES

안원기 Univ. of Texas at Arlington 2004 해외박사

The purpose of this study is to develop of a compact design tool that would be use to assist during layout/layup design to minimize warpage of a PWB during fabrication and reflow solder processes for electrical engineers. These results would enhance the quality and reliability of real product by minimizing PWB warpage and would reduce production cost because of minimizing repair needs on the production line. Also help in prediction of the parameters impacting warpage and assist the board designer as well as the board fabricator and assembler with minimizing warpage. The developed design guide distinguishes itself from the existing design guide in that the developed tool is not only compact but also efficient. This study has two main tasks. The first one is a thermo mechanical analysis, verification and parameterization of bare multilayer board design and their impact on board warpage in board fabrication process and through reflow solder process. The second one is design-analysis integration methodology for an effective thermo mechanical analysis of PWB. This thermo mechanical analysis includes the real model as well as the simplified model. These two stepwise tasks will be a guideline to develop a design tool. During fabrication and due to reflow solder process, this research describes how layup and layout design data is mapped into an intermediate analyzable representation which supports the information requirement of several thermo-mechanical analyses including product optimization. This research describes other issues encountered such as how to integrate product data that spans more than one tool, how to modify and add analysis data that is necessary during analysis, and how to use data stored in the analysis module from different programming environments. This analysis integration technique is necessary as a general link to design tools and commercial analysis tools in order to harmonize diverse data and add optimization /simplification and missing/modifying data.

Wetting dynamics and frequency responses of non-Newtonian coating liquids in slot coating processes

안원기 Korea University 2018 국내박사

This thesis is a study of flow dynamics, system stability and sensitivity analysis of slot coating process which is one of thin film manufacturing process. Numerical approach and experiment have been carried out to analyze the slot coating process, and a new method for manufacturing membrane us¬ing the slot coating process has been proposed. In the first part, the stability of the slot coating process by the flow dynamics inside the coated bead was analyzed using the visco-capillary model and two - dimensional coating bead simulation according to the rheological properties and process conditions of the solution. The wetting property of the solution can be characterized by the contact angle at the gas-liquid interface on the substrate, but analysis of the wetting property of the solution in the slot coating process was not performed because of difficulty in observing the coating bead region. In this study, the change of the meniscus shape was ana¬lyzed through precise observation of the coating bead region, and the effect of the contact angle variation on the operating window of the system stability was analyzed. In additions, double layer slot coating process was introduced to form a polymer layer at the liquid interface between the two solutions with different wetting properties. In the conventional interfacial polymerization pro¬cess, the manufacturing process is multistep, and the manufactured layer has poor durability. However, the thin layer produced by the double layer slot coat¬ing process has improved durability. In the second part, in order to consider the characteristics of the industrially applied coating solutions, the flow analysis of coating process using viscoelastic solution was performed. Based on the viscoelastic capillary model and the dynamic behavior of coating process using Newtonian solution, this study extended to the analysis of the two - dimensional coating bead flow for viscoelastic fluid. The constitutive equations used to portray viscoelastic fluids are Oldroyd-B and PTT models. The viscoelastic constitutive equation with nonlinear equations was calculated by Elastic-Viscous-Split Stress (EVSS) technique for numerical simulation. The process stability window obtained from the viscoelastic capillary model and the experiment was compared with the two-dimensional model extended in this study for verifying the numerical simulation method of this study. The stress difference due to the polymer inside the coating bead and the upstream and downstream velocity distributions in the coating beads were analyzed according to the process conditions. Also, the stress difference and the shape of the downstream free surface according to the viscosity ratio indicating the amount of polymer in the coating bead were analyzed, and the die swell phenomenon observed in the polymer processing was analyzed in slot coating process. In the third part, three-dimensional numerical simulations combining the flow inside the slot die and the coating bead flow were performed to improve understanding of the coating bead region. The effect of the flow inside the slot die on the coating bead and the final wet thickness was analyzed according to operating conditions. In particular, numerical simulation results of the edge-bead phenomenon at both ends of the film are compared with experimental results. In addition, three-dimensional numerical simulations were carried out by developing the existing stripe slot coating process study (Han et al. 2014), and the distribution of the width-direction film thickness for the non-Newtonian coating solution was studied. In addition, the effect of width coating gap vari¬ation occurring slot coating process operation was analyzed. The effect of the change of the slot die coating gap on the thickness distribution of the final film is analyzed, and especially the change of the edge- bead is analyzed. Also, the stability of the film was analyzed by observing the thickness of the film immediately after exiting the slot die and the thickness of the stabilized film. In the fourth part, the frequency response method was conducted to analyze thickness variations of the final film due to changes in operating condi¬tions that can occur in the coating process. The process control variables that can be perturbed in the slot coating process are flow rate, coating gap, sub¬strate velocity and vacuum device. In this study, the final film thickness variation according to the flow rate and coating gap change was analyzed. Especially, the variation of the final film thickness according to the flow rate was analyzed by changing the process time of the inside of the coating bead through the modification of slot die lip shape. It is confirmed that the film thick¬ness variation due to the flow rate disturbance is located on the same line from the correlation between the process time and the disturbance frequency. In addition, the frequency response of the slot coating process was consid¬ered the viscoelasticity of the solution. Since the flow rate changes in the coating process are governed by the overall mass balance, the viscoelastic properties of the solution are not affected by the sensitivity of flow rate dis¬turbance, but the change in coating gap is influenced by the viscoelasticity of the solution. In particular, the elongation properties of the solution affected the sensitivity, and as the extensional thickening became stronger, the sensitivity to the coating gap change was reduced.