A Frequency-Segmented Accelerated Vibration Test Method for Seat Frames Using Damage-Rate Ratio: A Comparative Study with IPL and FDS

To address the issues of lengthy vibration durability test cycles for seat frames and poor consistency of damage equivalence at different locations under multiaxial excitation in existing acceleration methods, this paper proposes a frequency-segmented accelerated vibration test method based on damage-rate equivalence. The method derives an analytical relationship between damage rate and stress spectral moments based on the Dirlik broadband damage estimation, enabling frequency-selective amplification of the acceleration PSD, thereby compressing test duration while maintaining a constant damage-rate ratio at critical nodes. The proposed method is implemented in three strategies—triaxial full-band, triaxial frequency-segmented, and uniaxial frequency-segmented—and compared with the inverse power law (IPL) and fatigue damage spectrum (FDS) methods. Through finite element analysis of a seat frame and dynamic force measurements on a six-degree-of-freedom hydraulic shaker, the damage-rate ratios at four structural nodes are used as indicators to evaluate each method. Results show that when the triaxial frequency-segmented strategy (DRR-TP) achieves the target damage-rate ratio of 0.25, the thrust increase is only 17.1%, substantially lower than the 21.0% increase from full-band acceleration, while displacement requirements remain nearly unchanged. At the calibrated node, DRR-TP provides accuracy comparable to FDS and better than IPL and the uniaxial strategy under the tested conditions. However, deviations exist across all methods at non-calibrated nodes, with IPL and the uniaxial strategy showing more pronounced deviations in this study. Furthermore, accelerated high-intensity road spectra may produce stresses approaching the yield limit, necessitating amplitude constraints. Overall, the DRR-TP method offers a favorable balance between efficiency and equipment feasibility, providing a practical framework for accelerated durability testing of seat frames.