is failure that occurs in structures that undergo repeated cyclic
stress, for example bridges and connecting rods.
In fatigue it is possible for failure to occur at stresses much lower than
the yield strength.
Fatigue is responsible for about 90% of all metallic component failures, and
it is also possible for polymers and ceramics to fail by fatigue.
It is catastrophic in that it occurs without warning because it is a brittle
fracture (with little or no plastic
deformation) that occurs in materials that are normally ductile.
There are three different modes of fatigue loading, shown