衝擊 荷重을 받는 金屬 材料의 動的 破壞 特性에 관한 硏究 = (A) Study on Dynamic Fracture Characteristics of Metallic Materials under Impact Loading

다국어 초록 (Multilingual Abstract)

This study is concerned with the determinations of dynamic crack initiation toughness(K_(Id)) and dynamic elastic-plastic fracture toughness(J_(Id)) of metallic materials at various temperatures, and utilizes Instrumented Charpy Impact Test as an experimental method. The load-time data needed for the evaluations of the toughnesses were obtained from the instrumented striking tup which has strain gauges in the form of Wheastone bridge circuit. To ensure the reliability and the accuracy of the obtained data they were critically scrutinized in view of the three criteria ; energy, limited frequency response and inertia effect. These are the general conditions that the load-time data from instrumented tests should satisfy to be considered as proper sets of data for further evaluations.
In this study dynamic fracture toughnesses were experimentally determined at various temperatures ranging from 20℃ ~ 400℃. Because of the dynamic nature of the test the unique inertia force develops inherently and exerts strong influences to crack initiation energies. The inertia forces are theoretically determined and compared with the those results obtained experimentally.
Specially, the dissipated energy due to the inertia forces is recognized to have serious consequences in dynamic tests. However, frequently the dissipated energy has not been considered in determining the crack initiation energy which is an important variable to evaluate dynamic elastic-plastic fracture toughnesses. In this study the dissipated energy due to the inertia force is computed for proper determinations of the crack initiation energy and further utilized to evaluate the dynamic fracture toughnesses.

목차 (Table of Contents)

• 목차 = Ⅰ
• ABSTRACT = Ⅲ
• List of Figures = Ⅳ
• List of Tables = Ⅷ
• Nomenclature = Ⅸ
• 제1장 서론 = 1
• 1-1. 연구의 배경 = 1
• 1-2. 연구의 동향 = 2
• 1-3. 연구의 목적 = 3
• 제2장 기본이론 = 4
• 2-1. 재료 강도에 대한 파괴역학적 고찰 = 4
• 2-1-1. 파괴역학의 기본개념 = 4
• 2-1-2. 응력확대계수 = 5
• 2-1-3. 평면변형 파괴인성 = 9
• 2-1-4. J 적분 = 10
• 2-2. 파괴인성치 결정법 = 12
• 2-2-1. 균열개시점 결정법 = 13
• 2-2-2. 동적 균열개시인성치 결정법 = 14
• 2-2-3. 동적 탄소성파괴인성치 결정법 = 16
• 2-3. 계장화 충격시험의 고유특성 = 17
• 2-3-1. 관성 효과(Inertial Effects) = 17
• 2-3-2. 한계 주파수 응답(Limited Frequency Response) = 22
• 2-3-3. 에너지 기준(Energy Criteria) = 24
• 2-4. 샤피충격시험에서 관성력에 대한 수학적 해석 = 25
• 2-4-1. 충격하중을 받는 시편변위에 대한 해석 = 25
• 2-4-3. 충격시험에서의 관성력 = 34
• 제3장 실험방법 및 절차 = 35
• 3-1. 실험장치 = 35
• 3-2. 시편 = 36
• 3-3. 실험방법 = 37
• 제4장 결과 및 고찰 = 42
• 4-1. 계장화 충격실험의 일반조건들의 만족여부 = 42
• 4-1-1. SM45C = 42
• 4-1-2. SS41 = 43
• 4-1-3. SKH-9 = 43
• 4-2. 동적파괴인성치 계산 = 44
• 4-2-1. SM45C = 44
• 4-2-2. SS41 = 47
• 4-2-3. SKH-9 = 50
• 4-3. 각 금속재료의 동적파괴특성 = 52
• 4-4. 각 시편의 파단면 고찰 = 54
• 제5장 결론 = 56
• 참고문헌 = 84
• 감사의 글 = 86