Benefits of Ultrasonic Peening Treatment in Fatigue Improvement of Welded Elements

Abstract

The Ultrasonic Peening (UP) is one of new and promising processes for fatigue life improvement of welded elements and structures. During the different stages of its development the UP process was also known as ultrasonic treatment (UT), ultrasonic impact treatment (UIT), ultrasonic impact peening (UIP). The beneficial effect of UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of material, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. The results of fatigue testing of welded elements made of regular and high strength steels in as-welded condition and after application of UP will be presented. The yield strength of considered materials varied from 250–350 MPa to 700–1000 MPa. It is shown that UP is the most effective and economic technique for increasing of fatigue strength of welded elements in materials of different strength. These results also show a strong tendency of increased fatigue strength of welded elements after application of UP with the increase in mechanical properties of the material used. It allows using to a greater degree the advantages of the HSS in welded elements, subjected to fatigue loading.