Capt. T.J. Cadeau, Sgt. M. Bunn of ATESS/DND .... Scenarios. MSD scenario: MSD approach. Standard Crack (SC) scenario: MSD approach. Primary crack.
Development of Advanced Risk Assessment Methodologies for Aircraft Structures Containing MSD/MED M. Liao, Y. Bombardier, G. Renaud, N. Bellinger, T. Cheung (DTAES/DND) Structures and Materials Performance Laboratory Institute for Aerospace Research
Acknowledgements This work was performed with financial support from the DRDC-NRC collaborative project “Quantitative Risk Assessment of CF Aircraft Structures” Project members: Dr. G. Renaud, Mr. Y. Bombardier, Dr. M. Khan, Dr. G. Li, Dr. M. Liao Dr. A. Fahr, Mr. N. Bellinger DND support: Mr. K. McRae of DRDC Mr. T. Cheung, Mr. Y. Caron, Mr. J. Gaerke of DTAES Capt. T.J. Cadeau, Sgt. M. Bunn of ATESS/DND 2
Contents • Risk Management for CF Air Fleets • NRC Risk Analysis Methods/Tools • MSD Damage Tolerance Analysis – MSD/MED crack growth analysis – MSD/MED residual strength analysis
• Risk Analysis for MSD/MED Structures – ICSD/EIFSD – Monte Carlo MSD crack growth analyses – Maximum Stress Distribution
• Probability of Failure (PoF) Results • Concluding Remarks • Future work
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Risk Management for CF Air Fleets RARM (Record of Airworthiness Risk Management) • Hazard Id. Risk Ass. Risk Ctrl. RARM Approval • Affecting all CF fleets (DND-AD-2007-01)
Risk Tracking
When “sufficient” data is available, Quantitative risk assessment (QRA) substantiates the assignment of a risk number in Qualitative risk assessment
TAM, C-05-005-001/AG-001, DTAES/DND, 2001
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NRC Risk Analysis Methods • NRC developed methods and tools to calculate the single flight hour probability of failure (PoF, ~hazard rate) based on extensive durability and damage tolerance analysis (DaDTA) and stress-strength interference model PoF (t ) = P[σ Max ≥ σ Critical (a, K C or σ RS )] = For Kc criterion: POF (a ) =
∞ 0
∞ 0
f (a) POF (a)da
f K C ( K C )(1 − H σ [σ C (a, K C )])dK C
For residual strength criterion : POF (a) = 1 − H σ [σ RS (a )] where H σ [σ ] is the maximum stress distribution per flight hour
• Crack size distribution update based on NDI and repair f a ,after ( a, t ) =
∞ 0
POD (a ) f a ,before ( a, t )da ⋅ f RCSD ( a, t ) + [1 − POD (a )] f a ,before ( a, t )
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NRC Risk Analysis Tools ProDTA Initial crack size distribution (ICSD/EIFS)
Maximum pit depth (Gumbel)
Crack growth curve and β-solution
Corrosion growth rate (Weibull / database)
Maximum stress (Gumbel / others) NDI POD (Log-logistic / others)
ProDTA
Corrosion protection breakdown time (Normal)
PoF
Failure criteria (KC, ac, σRS)
Corrosion POD/NDI error (Normal)
Fatigue inputs
Corrosion inputs
Re. ICAF 2005 paper
• ProDTA calculates the PoF using probability integration method or Monte Carlo technique 6 • ProDTA is under development, aiming to become a tool for CF fleets
Case Study: CC-130 Centre Wing MSD/MED Issue The crisis
The causes
C-130A catastrophic failure in Walker, CA. 2002
“fatigue cracks in the lower wing skin” and “multiple site fatigue damage/ MSD” (NTSB)
The method needed Advanced DaDTA and Risk Assessment Methodologies for Aircraft Structures Containing MSD/MED
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CC-130 Center Wing Lower Surface Panel Standard Crack (SC) scenario: single dominant crack, phase-byphase (PBP) approach (OEM DTA)
Multi-phase single crack growth analysis: Phases I & II ∅ 0.339” (BBR=1.587)
Phases III & IV ∅ 0.267”
Phases V & VI Phases VII & VIII 7075-T7351 0.22” thick VIII
CC-130 Center Wing, Lower Surface Panel, Location CFCW-1
VII VI V
IV III
I
II
SC-PBP (OEM analysis, duplication)8
Crack Growth Analysis Scenarios Standard Crack (SC) scenario: MSD approach Primary crack (0.050”)
Secondary cracks (0.005”)
SC-MSD
MSD scenario: MSD approach Primary crack (0.050”)
Secondary cracks (0.005”)
MSD 9
β-Library • Currently available & validated -functions: σtotal
σbypass Thickness (T) a φ
BBR=σbearing/σbypass
c
Corner crack σtotal
B
σbearing c B
Plate
2c
c D
W
B W
Crack
c Ligament failure Load path Stiffener
Stringer/Cap effect
σtotal
D=2R
σtotal
Radially crack at hole Edge crack through hole with bearing load
Crack approaching a hole
Good agreement between NRC closed-form 10 equations, OEM, and FEA (StressCheck)
β-Library • Additional available & validated -functions: σtotal * W/(W-Σci)
σtotal
σbypass BBR=σbearing/σbypass b A
B 2a1 Gap
C
D1
σbearing
D c1
2a2
c2
c2
B1
B
Crack interaction effect
c1
W
σtotal
D2 ci
c2
B2 W
σtotal
W
σtotal * W/(W-Σci)
Diametrically cracks at Linked-up crack Net section effect (under investigation) hole with bearing load
Good agreement between NRC closed-form 11 equations, OEM, and FEA (StressCheck)
Verification of MSD β-Solutions 2.2
2.2
CGCC130MSD (A11) CGCC130MSD (A12) STRESSCHECK (A11) STRESSCHECK (A12)
2.1 2
2 a22 and a31 merged
1.9
1.9
1.8
1.8
1.7
1.7
β -solution
β -solution
a32 merged with a41 and a41 merged with a51
2.1
1.6 1.5
a11 merged with left edge
1.6 1.5
1.4
1.4
1.3
1.3
1.2
1.2
1.1
1.1
CGCC130MSD (A11) CGCC130MSD (A12)
a12 and a21 merged
1 0
10
20
STRESSCHECK (A12)
1 30
a0 (mm)
STRESSCHECK (A11)
40
-solutions for the lead crack a0 (< 50mm)
50
50
100
150
200
250
a0 (mm)
-solutions for the lead crack a0 (50mm
