SHOT PEENING – PROCESS FEATURES

Abrasive is thrown at the surface of components that are still free of tension or stress to obtain a local distribution of compressive and tensile stress.

The abrasive hitting the surface at velocities of up to 100 m/s causes permanent spherical indentation. The metal layers below the peened surface undergo a deformation.

The equilibrium of the two forces produces a compressive stress within the metal. Due to the compression, the marks in the upper layers are tangential and perpendicular to the surface, whereas, in the lower layers, the tension causes a permanent deformation which is less pronounced than the one caused by compression.

Therefore, shot peened workpieces have undergone a preliminary stress before being put to actual use. The stress that the workpieces will be subjected to later on corresponds to the preliminary stress inflicted on them by shot peening. Especially in the case of tension, the previous compression of the surface will reduce the tension peaks. That is why shot peening improves fatigue strength.