What is shot peening?

Shot peening is a cold working process in which the surface of a part is bombarded with small spherical media called shot. Each piece of shot striking the material acts as a tiny peening hammer, imparting to the surface a small indentation or dimple. In order for the dimple to be created, the surface of the material must be yielded in tension.

Below the surface, the material tries to restore its original shape, thereby producing below the dimple, a hemisphere of cold-worked material highly stressed in compression. Nearly all fatigue and stress corrosion failures originate at the surface of a part. Further, it has been well established that cracks will not initiate or propagate in a compressively stressed zone.

Since the overlapping dimples from shot peening create a uniform layer of compressive stress at metal surfaces, the process provides considerable increases in part life. Compressive stresses are beneficial in increasing resistance to fatigue failures, corrosion fatigue, stress ... more.

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