TA1 titanium alloy self-piercing riveted joints fatigue service non-destructive monitoring via dynamic characteristics

Self-piercing riveting (SPR) is increasingly applied in lightweight structures; however, reliable non-destructive evaluation of its fatigue service state remains challenging due to inaccessible internal damage. In this study, the fatigue behavior of TA1 titanium alloy SPR joints was investigated through dynamic response characterization and strength degradation tests. The evolution of natural frequency under cyclic loading exhibited a distinct three-stage degradation behavior corresponding to damage initiation, stable crack propagation, and rapid failure. Based on this relationship, a frequency-based residual life prediction model was developed using a Weibull framework, achieving prediction errors below 5% over the entire fatigue process. In addition, residual strength tests conducted at representative fatigue stages enabled the establishment of a strength degradation model with errors below 3%. By coupling natural frequency variation with strength attenuation, a dual-parameter prediction model was proposed to simultaneously estimate residual life and residual strength from real-time dynamic response data. Experimental validation confirmed that the predicted results consistently fell within the 95% confidence intervals, demonstrating the robustness and accuracy of the proposed method.