Purpose This specification covers the equipment and process requirements for forming or straightening metal parts using Ultrasonically Activated Needle Peening Process Description Ultrasonic kinetic energy is transferred from a vibrating metallic element to the peen forming media (needles) contained in an end piece. See Figures 4 and 3 respectively. The equipment can be used manually by an operator or automatically in connection with a CNC machine@ e.g.@ an industrial robot. The equipment set (Figure 1) is composed of a central control unit and a machine held tool@ the peening head (Figure 2). Applications Ultrasonically activated needle peening is typically used to form and straighten metallic parts by inducing compressive residual stresses on selected surfaces in order to produce the desired part curvature. The process is successfully applied to part geometries for which the depth of introduced residual stresses is significant in comparison to part thickness at that location.