Definition - What does Peening mean?
Peening is a technique in which the surface of a metal is worked on so as to improve the properties of the metal. It can be done in three ways - shot peening, hammering and laser peening. It is used to weld the cast iron, flatten the sheet of metal and in other industrial pressing operations. When a metal undergoes Peening, it is tries to expand the surface laterally but it is prevented from doing so by the elastic nature of the subsurface. Peening encourages strain hardening of the metal.
Petropedia explains Peening
Peening tends to expand the surface of a metal by relieving tensile stress and inducing comprehensive stress. This process can be done with three different techniques. If the process involves bombardment of the metal surface then it known as shot peening. If the surface is impacted by two or more coated flaps then it is known as roto peening. If a descaling gun with a cluster of needles is used, the process is known as needle peening. Peening is beneficial because after a metal undergoes the process it resists the propagation of cracks and increases resistance to stress corrosion and fatigue failure.