Ultrasonic Needle Peening
A mechanical post-treatment process where locally oscillating needles create plastic deformation at weld toe transitions. This smooths the notch geometry and induces beneficial compressive residual stresses.
Ultrasonic needle peening is a post-treatment process for welds. The high-frequency vibrating needles work the weld surface and the weld transition. This smooths out notches and introduces compressive residual stresses into the surface layer. This makes the weld less sensitive to fatigue cracking and noticeably improves the fatigue strength. You guide the device evenly over the weld with moderate contact pressure. It is important that you cover the entire transition area from the base material to the weld. If you treat the weld completely and evenly, you get a clean, compacted surface. Staying too long in one spot doesn't hurt, but it doesn't do any good either.