Fatigue Strength Improvement of Aluminum and High Strength Steel Welded Structures using High Frequency Mechanical Impact Treatment

Abstract

Most structures and components are fabricated using welded joints. A very high percentage of all fatigue failures locally occur at welded locations due to high tensile residual stresses and stress concentrations resulting from the weld process. High frequency mechanical impact (HFMI) treatment has been increasingly used as an effective post-weld treatment technique to improve fatigue strength of welded structures. Fatigue tests have been conducted for as-welded and HFMI treated 5083-H321 grade aluminum and ASTM A514 steel welded specimens to investigate the effects of the HFMI treatment under constant amplitude R= 0.1 and variable amplitude loading. This paper presents fatigue test results including local properties (residual stresses) of welded specimens under the as-welded and the HFMI treated conditions. Test results showed that the HFMI treatment significantly improved fatigue life performance of the aluminum and steel welded specimens under both constant and variable amplitude load conditions. Therefore, the HFMI treatment is a quite promising post-weld treatment technique and its potential applications on the fatigue design of welded structures and components can lead to lighter structures and products, in which components and structures can be down-sized and optimized to reduce weights.