The definition of fatigue testing can be thought of as simply applying
cyclic loading to your test specimen to understand how it will perform
under similar conditions in actual use. The load application can either
be a repeated application of a fixed load or simulation of in-service loads.
The load application may be repeated millions of times and up to several
hundred times per second.
Why Do a Fatigue Test?
In many applications, materials are subjected to vibrating or oscillating
forces. The behavior of materials under such load conditions differs from the
behavior under a static load. Because the material is subjected to repeated
load cycles (fatigue) in actual use, designers are faced with predicting fatigue
life, which is defined as the total number of cycles to failure under
specified loading conditions. Fatigue testing gives much better data to
predict the in-service life of materials.