Before revision: In metallurgy, peening is the process of working a metal's surface to improve its material properties, usually by mechanical means, such as hammer blows, by blasting with shot (shot peening), or focusing light (laser peening).
After revision: In metallurgy, peening is the process of wpeening), or in recent years, with water column impacts (water jet peening) and cavitation jets (cavitationking a metal's surface to improve its material properties, usually by mechanical means, such as hammer blows, by blasting with shot (shot peening), or focusing light (laser peening).