Development Trend and Application of Peening Technology to Improve Welding Joint Life

Welding processes in various industries such as shipbuilding, railroads, aircraft, and construction are inevitably accompanied by HAZ(Heat Affected Zone) deformation and metal structure changes around the toe of the welding bead. It is widely known that it is very weak in terms of structural strength because the tensile residual stress is introduced by welding, and the surface is also rough, causing the main cause of stress concentration to occur. It also becomes the damage initiation cite to the welded structure. Post-welding heat treatment, grinder, and TIG dressing methods were used to release residual stress and to eliminate defects in the welding part. Recently, various peening technologies using pulsed heat sources of laser, elastic vibration energy of ultrasonic waves, compressed air or cavitation have been developed and are being actively utilized as performance improvement and standardized safety technologies in the field. The local peening process on the surface of the welded part and the welded heat-affected part is not only easily portable by various technical methods, but is also being applied to robots or hybrid-3D printing technology. Therefore, in this technical paper, the technical analysis of the various advanced peening technologies that are currently being utilized and the device development trend are evaluated. The portable ultrasonic peening equipment was developed and the recently applied technologies that are newly grafted to improve mechanical properties are introduced. Key words: Welding joint life, Micro shot peening, Laser shock peening, Ultrasonic peening, Ultrasonic impact treatment, Cavitation shotless peening