
7
Fatigue
7.1 Fatigue failure
In service many components undergo thousands, often millions, of changes of
stress.
Some are repeatedly stressed and unstressed, while some undergo
alternating stresses of compression and tension. For others the stress may just
fluctuate about some value. Many materials subject to such conditions fail,
even though the maximum stress in any one stress change is less than the
fracture stress as determined by
a
simple tensile test. Such
a
failure, as
a
result
of repeated stressing, is called
a
fatigue failure.
The source of the alternating stresses can be due to the conditions of use of a
component. Thus, in the cas ...