Shot peening

The process of applying a compressive stress to the surface of a part by bombarding the part with high-speed pellets, often made of glass or steel.

For parts that experience high tensile stresses at the surface and lower tensile stresses toward the interior (i.e., that have a stress gradient), shot peening can improve the fatigue life of the part. Such parts include slot ends and parts that are subjected to flexure stress. However, if not properly performed, shot peening can reduce the fatigue life.