PSI - Issue 75

Gary B. Marquis et al. / Procedia Structural Integrity 75 (2025) 530–537 Marquis, Barsoum & Leitner / Structural Integrity Procedia (2025)

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Table 2. Structural details that are recommended for use during verification testing of HFMI devices.

Qualification also requires thorough documentation of treatment parameters: indenter size and shape, number of passes, power settings, and tool orientation. Groove quality must meet specified depth (0.05–0.6 mm) and width (2– 6 mm) standards with at least 25–75% of groove width positioned in the weld metal. Measurement tools such as depth gauges and Almen-type strip fixtures provide verification of groove consistency and treatment intensity.

Figure 6. Symmetric double-sided attachments are recommended to avoid secondary bending. a) Longitudinal fillet welded gusset and b) double-sided transverse non-load carrying attachment. The Almen-type calibration test serves as a physical validation of treatment energy. A standard steel strip is treated under defined conditions, and the resulting curvature—measured with a dial gauge—indicates energy input and residual stress effects. This method offers an additional control for comparing HFMI devices or validating tool settings in the field. Device qualification must include reproducibility, ensuring results are not operator- or setup dependent. Together, this verification protocol provides a practical, non-commercial standard for assessing HFMI tools, helping ensure reliable fatigue strength improvement across diverse applications. 5. Conclusion and Future Direction HFMI treatment has matured into a validated and practical method for improving the fatigue strength of welded steel structures. Its dual mechanism—geometrical improvement at the weld toe and the induction of beneficial compressive residual stresses—makes it highly effective for both new and existing structures. In recent years, HFMI has seen widespread industrial adoption in sectors such as bridges, offshore structures, heavy machinery, railways, and wind energy, where fatigue performance is critical and structural access for repair is limited. The IIW recommendations have established clear procedures for treatment, quality control, and device verification, supporting reliable application in the field. The development of performance-based qualification standards ensures consistent results across different HFMI tools and operational environments. HFMI is also increasingly accepted in national and international design codes, further integrating it into mainstream engineering practice. Despite this