I, II, III

modes of crack surface displacement

A

crack area

A, m

constants in Basquin equation

a

crack length, half crack length of internal crack, crack radius, characteristic crack dimension, semi minor axis of ellipse

a _f

final value of a

a _i

initial value of a

?a

increment of crack propagation

B

specimen thickness, biaxiality ratio

C, m

constants in Paris equation

c

half crack surface length, semi major axis of ellipse

E

Young s modulus

E (k)

complete elliptical integral of the second kind

F

force

f

frequency

K

stress intensity factor, subscripts I, II, III denote mode

value of K _I for a small Mode I branch crack

K _Ic

plane strain fracture toughness

K _B

bending mode stress intensity factor

K _c

fracture toughness, plane stress fracture toughness

K _f

fatigue strength reduction factor

K _h

weighted average range of K _I

K _max

maximum value of K _I in fatigue cycle

K _{mi n}

minimum value of K _I in fatigue cycle

K _op

crack opening value of K _I

K _t

stress concentration factor

K _{? A}

antisymmetric mode stress intensity measure

K _{? S}

symmetric mode stress intensity measure

K _?

stress intensity measure

? K

range of K _I in fatigue cycle

? K