Symbols

D Fatigue damage calculated for a given period of service.

Dl Fatigue damage calculated for the full design life.

Ladh Effective length of adhesively bonded lap joints.

N Number (or total number) of stress range cycles.

Nj Endurance under stress range A<jj.

Nc Number of cycles (2 million) at which the reference fatigue strength is defined.

Nd Number of cycles (5 million) at which the constant amplitude fatigue limit is defined.

Nl Number of cycles (100 million) at which the cut-off limit is defined.

R Minimum stress divided by the maximum stress in a constant amplitude stress history or a cycle derived from a variable amplitude stress history. Also applies in the context of stress intensity.

Tf Time for a crack to grow from a detectable size to a fracture critical size.

Ti Inspection interval.

Tl Design life

Ts Safe life fv,adh Characteristic shear strength of adhesive kadh Fatigue strength factor for adhesive joints kN Number of standard deviations above mean predicted number of cycles of loading.

kF Number of standard deviations above mean predicted intensity of loading.

ld Minimum detectable length of crack.

If Fracture critical length of crack m Inverse slope constant of a log A a - log N fatigue strength curve.

m2 Value of m for 5 x 106 < N < 108 cycles, iij Number of cycles of stress range Ao{.

yFf Partial safety factor for fatigue load intensity.

YMf Partial safety factor for fatigue strength.

(Jmaxj GminMaximum and minimum values of the fluctuating stresses in a stress cycle.

A a Nominal stress range (normal stress).

Aciadh Effective shear stress in adhesive.

Agc Reference fatigue strength at 2 million cycles (normal stress).

Agd Constant amplitude fatigue limit.

AaL Cut-off limit.

Agr Fatigue strength (normal stress).

log Logarithm to base 10.

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