ABSTRACT Titanium alloys, notably TC4 (Ti‐6Al‐4V), are critical for aerospace structural components, yet fastener holes within them serve as stress concentration sites prone to fatigue crack initiation. Cold expansion strengthening is a prevalent technique to enhance fatigue life by introducing beneficial compressive residual stresses around these holes. This study systematically investigates the influence of two core process parameters—expansion amount and reaming depth—on the resultant residual stress field and fatigue life enhancement in TC4 alloy. A combined approach of experimental testing and finite element simulation using ABAQUS was employed. The results elucidate that increasing the expansion amount elevates both tangential and radial residual stresses, significantly improving fatigue life; however, excessive expansion induces material damage. Conversely, while reaming improves surface integrity, excessive reaming diminishes the compressive residual stress layer, thereby reducing the fatigue benefit. Optimal parameter combinations were identified for typical structures (A40 and A50), achieving a maximum fatigue life improvement of up to 30 times compared with untreated specimens. This research provides optimized process guidelines and a deeper understanding of the parameter interactions for cold expansion in critical aerospace applications.
Hu et al. (2026) studied this question.