표제지
목차
1. 서론 10
1.1. 연구 배경 및 목적 10
1.2. 연구 동향 11
1.3. 연구 내용 12
2. 관련 이론 13
2.1. 누적 손상법 13
2.2. 랜덤 진동 15
2.3. 확률 밀도 함수 17
2.4. 랜덤 프로세스 19
2.5. 주파수 영역에서의 랜덤 진동 23
2.5.1. 푸리에 변환 23
2.5.2. 주파수 반응 함수 25
2.5.3. 파워스펙트럼 밀도 28
2.5.4. 파워스펙트럼 모멘트 31
2.5.5. 불규칙 계수 33
2.5.6. Narrowband 방법 35
2.5.7. Dirlik 방법 36
2.5.8. Lalanne 방법 38
2.5.9. Steinberg 방법 39
3. 재료 및 해석방법 41
3.1. 해석 물성치 41
3.2. 유한요소 모델링 42
3.2.1. 직사각형 노치 빔 42
3.2.2. 매쉬 정교화 해석 44
3.3. PSD 진동 해석 46
3.3.1. 주파수 대역별 해석 49
3.3.2. PSD 분석 방법별 해석 51
3.3.3. PSD 진동 피로 해석 과정 52
4. 해석 결과 및 고찰 54
4.1. 노치 빔에 대한 MIL-STD-810G 주파수 대역 분석 54
4.1.1. Dirlik 방법의 피로 손상 및 수명 54
4.1.2. MIL 규격 주파수에서의 PSD 예측 방법 비교·분석 59
4.2. 노치 빔에 대한 MIL-STD-810G 저주파 대역 분석 62
4.2.1. Dirlik 방법의 피로 손상 및 수명 62
4.2.2. 저주파에서의 PSD 예측 방법 비교·분석 66
4.3. 노치 빔에 대한 MIL-STD-810G 고주파 대역 분석 69
4.3.1. Dirlik 방법의 피로 손상 및 수명 69
4.3.2. 고주파에서의 PSD 예측 방법 비교·분석 73
5. 결론 76
6. 참고문헌 77
ABSTRACT 81
Table 2-1. The concept of stationary characteristics 22
Table 2-2. Formula related to the irregularity factor 34
Table 3-1. The mechanical material properties of Al6061-T6 41
Table 3-2. Nodes and elements of notched beam 43
Table 3-3. Mesh number and stress magnitude 45
Table 3-4. MIL-STD-810G Input parameter 47
Table 3-5. MIL-STD-810G Input parameter 1/55 scale down 48
Table 3-6. Analysis for each frequency band in Dirlik method 50
Table 4-1. Damage and life in MIL-STD-810G frequency range 58
Table 4-2. Damage and life in low frequency range 65
Table 4-3. Damage and life in high frequency range 72
Table 4-4. Result of damage and life in notched beam of Dirlik method 75
Fig. 2-1. Non-consistent amplitude load 14
Fig. 2-2. Random vibration load data in time domain 15
Fig. 2-3. Random vibration load data t₀ in time domain 16
Fig. 2-4. Calculation of PDF p(x) in random history 18
Fig. 2-5. Different outputs within the same time (Ensemble) 19
Fig. 2-6. Stationary and ergodic in random vibration 21
Fig. 2-7. Fourier transform and inverse fourier transform 24
Fig. 2-8. Example of fourier transform vibration 24
Fig. 2-9. Transfer function relating input force to output amplitude 25
Fig. 2-10. General excitation function y(ψ) 28
Fig. 2-11. Example of power spectral density 30
Fig. 2-12. The definition of spectral density moments 31
Fig. 2-13. Expected zero, expected peak and the irregularity factor 33
Fig. 2-14. Gaussian distribution 39
Fig. 2-15. Calculation of the PDF from the stress range histogram 40
Fig. 3-1. Geometry and 2-D drawing of the notched beam 42
Fig. 3-2. Fixed support of notched beam (■) 44
Fig. 3-3. Stress tendency according to mesh size 45
Fig. 3-4. PSD standard(MIL-STD-810G) 46
Fig. 3-5. PSD standard 1/55 scale of MIL-STD-810G 49
Fig. 3-6. Basic flowchart of PSD vibration fatigue analysis 53
Fig. 4-1. Damage of notched beam in the MIL-STD-810G frequency range (Dirlik method) 55
Fig. 4-2. Life of notched beam in the MIL-STD-810G frequency range (Dirlik method) 56
Fig. 4-3. Notched part of the aluminum beam damage in the MIL-STD-810G frequency range (Dirlik method) 57
Fig. 4-4. Notched part of the aluminum beam life in the MIL-STD-810G frequency range (Dirlik method) 57
Fig. 4-5. Distribution of stress range for the Dirlik method 59
Fig. 4-6. Comparison of stress range for the PSD method (Excluding Steinberg) 59
Fig. 4-7. Comparison of stress range for the PSD method (Including steinberg) 60
Fig. 4-8. Damage of notched beam in the MIL-STD-810G low frequency range (Dirlik method) 62
Fig. 4-9. Life of notched beam in the MIL-STD-810G low frequency range (Dirlik method) 63
Fig. 4-10. Notched part of the aluminum beam damage in low frequency range (Dirlik method) 64
Fig. 4-11. Notched part of the aluminum beam life in low frequency range (Dirlik method) 64
Fig. 4-12. Distribution of stress range in low frequency for the Dirlik method 66
Fig. 4-13. Comparison of stress range in low frequency for the PSD method (Excluding Steinberg) 66
Fig. 4-14. Comparison of stress range in low frequency for the PSD method (Including Steinberg) 67
Fig. 4-15. Damage of notched beam in the MIL-STD-810G high frequency range (Dirlik method) 69
Fig. 4-16. Life of notched beam in the MIL-STD-810G high frequency range (Dirlik method) 70
Fig. 4-17. Notched part of the aluminum beam damage in high frequency range (Dirlik method) 71
Fig. 4-18. Notched part of the aluminum beam life in high frequency range (Dirlik method) 71
Fig. 4-19. Distribution of stress range in high frequency for the Dirlik method 73
Fig. 4-20. Comparison of stress range in high frequency for the PSD method (Excluding Steinberg) 73
Fig. 4-21. Comparison of stress range in high frequency for the PSD method (Including Steinberg) 74