Experimental evaluation of HFMI effectiveness for Weld Repairs

Abstract One of the methods to increase the fatigue life of welds is the HFMI (High Frequency Mechanical Impact) treatment, which involves creating compressive stress in the weld surface and improving the notch geometry around the weld toe. In this study, fatigue tests were conducted on specimens loaded by four-point bending. The benefits of the HFMI method were compared to specimens without post-welding treatment (as welded). The loading was applied at several levels with constant stress range amplitude and stress ratio (parameter R). The impact of the HFMI method was also investigated for steels of different strengths, ranging from S355 to S960. After completing the fatigue tests and the initiation of fatigue cracks, the welds were repaired and the HFMI treatment was applied again. These repaired specimens were loaded with the same parameters as in the case of the previous specimens. Finally, the benefits of the HFMI method for both new and repaired welds were compared and evaluated, depending on the specific loading conditions and material strength. The results show an increase in cycles to failure when using the HFMI method for both new and repaired welds. This has significant potential for future repair and reconstruction of bridge structures damaged by fatigue.