압력 하중을 받는 곡면 패널의 3차원 비선형 구조해석의 신뢰성 연구

다국어 초록 (Multilingual Abstract)

Recently, in the aerospace industry, the importance about analysis is increasing, demanding more accurate and reliable results for structural integrity. Therefore, one common approach in the aerospace industry is to evaluate the structural integrity of the structures using commercial FEM programs, which are based on the finite element method.
Sheet metal components such as the aircraft's external skin or inlet duct skin are usually designed with curvature to enhance aerodynamic efficiency. Additionally, for weight reduction, the process of Chemical Milling, which involves controlled corrosion to adjust the thickness, is applied. In such cases, stress concentration occurs in the area for rapidly decreased thickness due to chemical milling. However, these challenges can be mitigated by applying reinforcement measures such as application of stiffeners or thickness increase to ensure structural integrity.
Generally, when analyzing panel with curvature subjected to pressure loads normal to the surface, linear analysis results in the same stress distribution regardless of the load direction, with internally applied loads yielding results with opposite signs. However, in nonlinear analysis, if the panel is subjected to bursting loads (positive pressure, acting from the concave side outboard), it exhibits similar behavior to the linear analysis. On the other hand, when subjected to crushing loads (negative pressure, acting from the convex side inboard), the panel's displacement changes abruptly even with a slight increase in pressure, leading to the occurrence of oil canning phenomena, which depend on the panel's curvature, thickness, load magnitude, and shape.
In this study, we investigated the difference between linear and nonlinear analyses when applying pressure normal to the surface of panels with curvature and chemical milling. Furthermore, we examined stress concentrations at the edge, which is the weak point, when oil canning phenomena occur. We also evaluated the structural effect for reinforced designs, such as a application of stiffeners or thickness increase, to prevent oil canning. Finally, reliability of the analysis is confirmed by comparing the predicted values with structural tests.

목차 (Table of Contents)

• 목 차 i
• 표 목차 iii
• 그림 목차 iv
• ABSTRACT v
• Ⅰ. 서 론 1
• 1.1 연구 배경 1
• 1.2 Chemical Milling 공법 2
• 1.3 Oil Canning 현상 4
• 1.4 연구 목적 및 범위 6
• Ⅱ. 이론적 배경 7
• 2.1 선형 정적 해석 7
• 2.1.1 선형 해석 7
• 2.1.2 정적 해석 8
• 2.1.3 유한 요소 해석의 선형 정적 해석 9
• 2.2 선형 좌굴 해석 10
• 2.2.1 탄성 좌굴 10
• 2.2.2 유한 요소 해석의 선형 좌굴 해석 11
• 2.3 비선형 해석 12
• 2.3.1 기하 비선형 14
• 2.3.2 재료 비선형 14
• 2.3.3 접촉 비선형 14
• 2.4 구조 강도 평가방법 15
• Ⅲ. 구조 시험 16
• 3.1 구조 시험 16
• 3.1.1 구조 압력 시험 16
• 3.1.2 측정기기 17
• 3.1.3 데이터 획득 시스템 17
• Ⅳ. 해석 결과 18
• 4.1 하중 및 FE Model 구성 18
• 4.1.1 해석 적용 하중 18
• 4.1.2 해석 모델 구성 19
• 4.1.3 재료 물성치 적용 20
• 4.2 선형 해석 결과 22
• 4.2.1 선형 해석 결과 22
• 4.2.2 선형 좌굴 해석 결과 24
• 4.3 비선형 해석 결과 25
• 4.3.1 비선형 해석 결과 25
• 4.3.2 선형 - 비선형 해석 결과 비교 30
• 4.4 Oil Canning 방지 설계 방안 32
• 4.5 구조 압력 시험 결과 35
• 4.5.1 Strain Gage 부착 35
• 4.5.2 시험 - 비선형 해석 변형율 결과 비교 36
• Ⅴ. 결론 37
• 참 고 문 헌 39