What is stress peening?

Stress peening is a variant of shot peening in which the part is peened while held under an elastic load that reproduces the direction of the stress it will bear in service. When the load is released, the applied stress adds to the compression left by peening, and the result is a greater and deeper residual compression precisely on the face that will work in tension —which is where fatigue cracks initiate.

It is used in components with a dominant load direction and high fatigue demand: leaf and parabolic springs, torsion bars and suspension springs, in both automotive and railway applications. The logic is simple: if the part will work under bending, it is best to peen it under bending.

It differs from conventional shot peening —done without load— and from double shot peening —two passes with different shot sizes—; these approaches are combinable, not mutually exclusive.

To learn when it is worth specifying, how the load is defined and how the process is controlled, see the stress peening technical article.

CYM builds stress peening machines with tensioning devices that reproduce the service conditions of the component.