Shot peening processes are based on the Almen effect. In short, it develops the effect generated by the impact of spherical shot on metallic surfaces generating a controlled compressive surface tension. This stress eliminates or undermines other previous stresses generated in previous processes such as thermal or mechanical.
The practical result is a significant increase in fatigue strength when parts are subjected to mechanical stresses such as torsion, compression, etc. This makes it an essential process for the manufacture of many aeronautical, automotive, energy and many other components.
These are processes that require a high level of technology with scrupulous control systems for shot control and screening of the operating mixture.