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Shot Peening

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Shot peening is a cold working process similar to sandblasting. Also called "shot blasting," it is used to modify the mechanical properties of metal by producing compressive residual stress layers on the material's surface. Shot of various mediums, such as round metallic pellets, glass beads, or ceramic particles, are impacted on the work surface at high speeds, creating plastic deformation. Though the process by which the blasting media is delivered is similar to sandblasting, the mechanism by which it works is different. Sandblasting relies on abrasion; shot peening depends on plasticity, with each projected particle operating like a ball-peen hammer. The shot peening process, in general, removes less material and produces less dust than does sandblasting.

Shot Peening Benefits

Shot peening changes the mechanical properties of a surface by spreading it plastically. The process can be used to relieve tensile stresses caused by grinding, turning them into beneficial, residual compressive stresses. Compressive stress on the surface can give metals increased resistance to fatigue and to certain types of stress corrosion. In certain instances, fatigue life of a treated material can be increased up to 1000% with shot peening. Shot peening can also dramatically increase the cycle life of welds. An SAE Fatigue Design and Evaluation Committee study showed that standard, non-shot peened welds would typically fail after 250,000 cycles, while welds