ZK60A 마그네슘 합금의 압출 조건에 따른 석출상 형태의 변화

학위논문(석사)--아주대학교 일반대학원 :에너지시스템학과,2015. 2최근 환경,에너지 문제로 인해 이산화탄소 배출을 줄이기 위한 수송기 기 연비 향상 효율에 관심이 집중되고 있다.연비 향상을 위해서는 소재 의 경량화가 요구되는데,경량화 소재로서 마그네슘의 적용범위가 넓어지 고 그 수요 또한 증가하고 있다.마그네슘 합금은 상용 합금 중 최적의 경량소재로서,우수한 주조성 및 비강도 뿐 아니라 자원이 풍부한 장점이 있어 알루미늄을 대체할 경량소재로 많은 연구가 진행되고 있다. 그러나 마그네슘 합금은 HCP 구조로 인해 상온에서 성형이 어렵고,알 루미늄 합금에 비해 강도가 낮은 단점이 있으나 고온에서 압출,단조 등 의 공정을 통해 합금의 강도를 향상시킬 수 있다. 본 연구에서는 마그네슘 ZK60A 합금 연속 주조재를 6:1과 10:1의 압출 비로 압출해 압출 영향에 따른 석출상의 변화를 관찰하였다.EBSD를 이 용하여 grain structure 및 grain misorientation 분포 등을 분석하고, TEM,EDS 분석을 통해 압출 전/후 석출상의 거동을 분석하였다.차례(TableofContents) 초록(Abstract)··································································ⅳ 그림차례(ListofFigures)·····················································ⅴ 표 차례(ListofTables)·······················································ⅵ 1.서론 ·············································································1 2.이론적 배경 ····································································2 2.1.마그네슘 합금의 일반적인 특성 및 동향 ·······························2 2.1.1.마그네슘 합금의 최근 동향 ···········································2 2.1.2.전자파 차폐성 우수 ····················································3 2.1.3.구조적 특성 ······························································3 2.2.ZK60A 합금의 조성 및 첨가 원소의 영향 ·····························6 2.3.마그네슘 합금 압출재의 강화기구 ······································10 2.3.1.가공 경화 ·······························································10 2.3.1.1.정의 ··································································10 2.3.1.2.Hall-Petchequation···············································10 2.3.1.3.Slipsystem ························································11 2.3.1.4.마그네슘 합금의 쌍정 변형 ·······································15 2.3.2.고용 강화 ·······························································17 2.3.3.석출 경화 ·······························································17 2.3.3.1.석출상에 의한 강화 메커니즘 ····································17 2.3.3.2.석출상 생성 메커니즘 ·············································18 2.3.3.3.마그네슘 합금 압출재의 석출상 생성 메커니즘 ···············23 3.실험 방법 ····································································25 3.1.압출 공정 ··································································25 3.2.성분 분석 ··································································27 3.2.1.ICP 분석 ································································27 3.2.2.X-RayDiffraction(XRD)분석 ·······································29 3.3.미세조직 분석 ·····························································31 3.3.1.ElectronBackScatteredDiffraction(EBSD)분석 ·················31 3.3.2.TransmissionElectronMicroscope(TEM)분석 ··················33 4.결과 및 고찰 ·································································35 4.1.마그네슘 합금 압출재의 성분 분석 ····································35 4.1.1.ICP 분석 ································································35 4.1.2.XRD 분석 ······························································38 4.2.마그네슘 합금 압출재의 미세조직 분석 ·······························40 4.2.1.EBSD 분석 ·····························································40 4.2.2.TEM 분석 ······························································45 4.2.2.1.입계 석출상 ·························································45 4.2.2.2.입내 석출상 ·························································51 4.2.2.3.석출상의 EDS 분석 ················································54 4.2.2.4.석출상의 기지 내 orientation·····································56 5.결론 ···········································································58 참고문헌(Reference)····························································59Maste

Improvement of High Speed Stability of Air Journal Bearing with Slot Restrictor

Externally pressurized air journal bearing is widely used in high speed rotating machinery and high precision spindle system because of its advantages such as low friction, low heat generating characteristics and averaging effect of the pressure deviation in the air film in bearing. And slot restrictor air journal bearing has high load capacitance and high stiffness. Stability characteristics of slot restrictor air journal bearing are studied theoretically to forecast and to prevent the whirl instability and to supply the basic data about the design variables of precision slot restrictor air journal bearings. As for the high speed rotating machinery, the instability called ‘whirl’ occurs, rubbing contact between the journal and bearing occurs mostly and the bearing-rotor system is destroyed ultimately. Therefore, the forecasting and prevention of the occurence of whirl instability is a very important subject especially to develop highly efficient high speed machinery. The bearing with the slot restrictor that varies about circumferencial direction is used for the purpose of the prevention of whirl instability

원주방향 변화를 갖는 슬롯 레스트릭터 베어링의 성능 연구

A slot restrictor air journal bearing has high load capacity and high stiffness. The stability characteristics of the slot restrictor air journal bearing are studied theoretically and experimentally to forecast and to prevent the whirl instability. As for the high speed rotating machinery, the instability called whirl occurs when the rotor rotates at a speed more than twice the resonant speed. Once the whirl occurs, rubbing contact between the journal and the bearing occurs mostly and the bearing-rotor system is destroyed ultimately. Therefore, the forecasting and prevention of the occurrence of whirl instability is a very important subject especially to develop highly efficient high speed rotating machinery. The bearing with the slot restrictor that varies about circumferential direction is used for the purpose of the prevention of whirl instability.한국과학재단 지원 목적기초연구(94-0200-05-03-3

제7회 충남 협동조합 연구포럼 '새마을금고의 정체성과 과제' (김영수,박정구)

1. 연구포럼 개요 ○ 기간: 2013년 4월 17 (수) 14:00~17:00 ○ 장소: 충남발전연구원 1층 회의실 ○ 대상: 협동조합․사회적기업․마을기업․자활부문 사회적경제 조직 대표 및 종사자, 관련 연구자, 활동가, 공무원, 일반 시민 등 2. 연구 포럼 목적 ○ 협동조합기본법 제정과 기존 협동조합의 정체성 확립, 협동조합의 지역사회 기여 등에 대한 이해를 도모 ○ 협동조합에 대한 지평을 넓히고 충남 협동조합 발전을 위한 다양한 논의를 진행 - 이후 생략￭[제1주제]새마을금고 운영현황과 문제점 (김영수 남서울대 세무학과 교수) I.개요 II.태동과 역할 III.업무 현황 IV.당면 문제점 V.추진할 과제와 방안 VI.정체성과 가치성 현주소 VII.협동금융조직으로서 정체성과 가치와 지향 업무 VIII.맺으며 ￭[제2주제]대구 원대새마을금고의 현황과 사업개관 (박정구 원대새마을금고 前 이사장) I.설립과 연혁 II.일반 현황 (2013.02.28 현재) III.조직도 (2013.02.28 현재) IV.연도별 성장현황 V.공제계약 현황 (2013.02.28 현재) VI.원대새마을금고의 이념 VII.경영방침 VIII.공동사업 투자방침 IX.복지사업 방침 X.복지사업 종류 및 운영 XI.기

Prediction of Noise and Vibration Characteristics of Externally Pressurized Air Journal Bearings with a Circular Slot Restrictor

The purpose of this paper is to investigate the noise and vibration characteristics of externally pressurized air journal bearings with a circular slot restrictor. To do this, the nonlinear transient analysis including rotor imbalance was performed for a rotor-bearing system. The effects of radial clearance and the length of the bearing and mass eccentricity of the rotor on the noise and vibration characteristics of the bearing are also examined. The results show that the noise and vibration of the rotor-bearing system first increase up to critical speed of the system, and then decrease up to instability threshold speed of the system as the rotational speed of the rotor increases, and the noise of the bearing is markedly influenced by the mass eccentricity of the rotor and the radial clearance and the length of the bearing.산업기반기술개발사업(A03-A07-2207-01