Shot peening is a cold work process used to enhance the life of metal components, to prevent fatigue, stress corrosion failures and prolong the product life for the component part.
Fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localised structural damage that occurs when a material is subjected to a cyclic loading.
Fatigue occurs when a material is subjected to repeated loading and unloading. If the loads are above a certain threshold point microscopic cracks will begin to form at the stress concentration points, such as the surface, sharp points in the deviation in shape and the internal grain structure. Eventually a crack will reach a critical size, the crack will elongate suddenly, and the component will break.