Fatigue tests of as-welded and HFMI treated S355 details with longitudinal and transverse attachments

Fatigue of welded steel details is a very complex phenomenon influenced by many factors. To improve its fatigue strength by extending the crack initiation period in total fatigue life, high-frequency mechanical impact (HFMI) method can be employed. The previously developed two-stage model (TSM), which considers the crack initiation and propagation periods separately, can take all HFMI improvement parameters. High cycle fatigue tests have been conducted to collect the necessary data for the calibration of the TSM. This paper presents fabrication, HFMI treatment, geometry inspection, monotonic tensile tests of the base material, and fatigue tests of as-welded and HFMI-treated details with longitudinal and transverse attachments. HFMI treatment’s quality control is emphasized, extending from the HFMI gauge’s standard application to the 3D scan of specimens. Additionally, the continuous monitoring system for crack initiation and propagation data collection is also presented. The obtained results and the observations during the tests are described in detail. It is shown that the HFMI method significantly extends the fatigue life of welded steel details, and data for the calibration of the TSM are presented.