102 / 352
98
Figure 10: The effect of
R
value on
the fatigue crack growth of a steel St
42-2 (DIN) /22/
Figure 11:
R
value effects on threshold and fracture
instability behaviour of 300M steel /8/
Figure 12: Effect of grain size on fatigue crack
growth of Waspaloy super alloy /23/
Figure 13: Fatigue crack propagation behaviour
of various polymers /24/
In addition, many of the conventions used in plane-strain fracture toughness testing,
ASTM E-399 /26/, are also used in FCGR testing. For tension-tension fatigue loading, the
K
Ic
loading fixtures frequently can be used. For this type of loading, both the maximum,
P
max
, and
P
min
, minimum loads in a cycle are tensile, and the load ratio,
R
=
P
min
/
P
max
, is
in the range 0 <
R
< 1. A ratio of
R
= 0.1 is commonly used for comparative purposes.