Abstract
Classical procedures for aircraft structural design involve assessing the various loading situations which may occur during the lifetime, estimating the extreme values of the loads in each of these situations — limit loads — multiplying these by a factor of safety, usually 1.5, to give the ultimate design load, and ensuring by calculation that the structure would avoid permanent deformation at the limit loads, and collapse at the ultimate design loads.
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Abbreviations
- D :
-
fatiue damage befote crack initiation.
- f(H), f(U o), f(V):
-
probability fensity of H, U o or V.
- f(t):
-
probability density of failures at time t.
- f(n):
-
fraction of original population failing at (discrete) load cycle n.
- F(t), F(n):
-
unreliability, probability of failure before time t or load cycle n.
- F(V):
-
probability of an applied load less than V.
- F(τ):
-
proportion of structures rejected by inspection at time τ.
- H, H i , H w , H F :
-
characteristic strength decay time, time to crack initiation, to fatigue weakening, to strength collapse.
- k i , k w , k F :
-
H i /H, H w /H, H F /H.
- l, l cr , l d , l r , l o :
-
crack length, critical crack length at which U = 2U o/3, crack detection threshold, crack length for rejection, initial crack size.
- m(V), m o :
-
frequency of loads exceeding V, frequency of exceeding threshold of measurement of V.
- n :
-
number of load applications.
- P(V):
-
relative frequency, probability that a measurable load exceeds V.
- r, r o , r e , r c :
-
risk rate, risk with virgin strength preserved, approximate risk, risk with continuous inspection and rejection.
- r ic :
-
risk with initial cracks.
- r(t/τ):
-
risk at time t after an inspection at time τ
- R, Ro, Re, Rc :
-
reliability, reliability with strength preserved, approximate value, with continuous inspection.
- R(t|τ):
-
reliability at time t after an inspection at timr τ.
- U, U o , Ũ 0, U 02 :
-
strength, virgin strength, median value, strength at a second independent location or mode of failure.
- V :
-
applied load.
- α:
-
fraction of population.
- Δ:
-
fatigue damage capacity of an indibidual prior to crack initiation.
- ø :
-
functional relationship of crack length to time (and H).
- ψ:
-
functional relationship of strength of crack length.
- ξ:
-
functional relationship of strength to time.
- τ:
-
inspection time.
- μ H :
-
underlying population mean of H, sampled to establish input data for calculation.
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© 1987 Springer Science+Business Media Dordrecht
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Hooke, F.H. (1987). Aircraft structural reliability and risk analysis. In: Provan, J.W. (eds) Probabilistic fracture mechanics and reliability. Engineering Application of Fracture Mechanics, vol 6. Springer, Dordrecht. https://doi.org/10.1007/978-94-017-2764-8_3
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DOI: https://doi.org/10.1007/978-94-017-2764-8_3
Publisher Name: Springer, Dordrecht
Print ISBN: 978-90-481-8297-8
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