S-N Curve

In high-cycle fatigue situations, materials performance is commonly characterised by an S-N curve, also known as a Wöhler curve. This is a graph of the magnitude of a cyclical stress (S) against the cycles to failure (N). An important characteristic to this plot is the fatigue limit.
 
The significance of the fatigue limit is that if the material is loaded below this stress, then it will not fail, regardless of the number of times it is loaded.
 
Impact of UIT
UIT introduces compressive stresses up to 2.5 mm in depth and relaxation of residual tensile stresses up to 15 mm in depth.
 
This results is an extended fatigue life, as proven by several independent research institutes. A few results can be seen in the S-N Curve.