| Abstract Scope |
This study investigates the efficacy of ultrasonic impact treatment (UIT) in enhancing the fatigue resistance of high-strength steel subjected to pre-fatigue loading, simulating the conditions of aged components. The methodology involves pre-fatiguing the steel at various levels (e.g., 70%, 80%) of its mean fatigue life, followed by UIT application. Rotational bend fatigue tests show significant improvements in the fatigue performance of pre-fatigued samples, often surpassing the as-received materials.
Finite element analysis reveals that UIT introduces a compressive stress field beneath the pre-fatigue crack tip, which shifts deeper as the crack grows, with maximum compressive stress always below the crack tip. High-resolution electron backscatter diffraction (HR-EBSD) analysis shows a severely plastically deformed zone around the crack tip, contributing to crack closure effects. Additionally, plastic deformation deflects the crack from the perpendicular direction, retarding crack extension. These factors collectively lead to a significant enhancement in the fatigue life of pre-fatigued specimens. |