A coherence-driven method for instability frequency identification and uncertainty evaluation in friction stir welding
Year: 2026
Type: article
Abstract: • A coherence-driven framework is proposed to analyze FSW nonstationary vibrations. • Coherence masking isolates physically correlated spectral components. • Spectral Flatness, Bandwidth, and Centroid quantify stability transitions. • Monte Carlo propagation provides uncertainty for all spectral indicators. • Method discriminates stable, transitional, and unstable FSW regimes. Friction Stir Welding (FSW) exhibits non-stationary vibrations that challenge conventional vibration-based monitoring, where stability indicators are often extracted from single-sensor spectra without formal uncertainty assessment. This study proposes a coherence-filtered spectral framework for the quantitative evaluation of dynamic stability in FSW. Magnitude-squared coherence between translational acceleration and rotational velocity is used as a filtering criterion to restrict feature extraction to dynamically correlated frequency bands. Within these bands, Spectral Flatness (SF), Spectral Bandwidth (BW), and Spectral Centroid (FC) are employed as stability-related descriptors. Experiments conducted on aluminum alloy lap joints at 1400, 1800, and 3200 rpm show that stable regimes are associated with low SF (<0.1), narrow BW (<20 Hz), and relative uncertainties below 10%, whereas unstable conditions exhibit broadband spectra, loss of feature separability, and uncertainty levels up to 30%. Measurement uncertainty is evaluated through Monte Carlo propagation of inertial sensor noise and bias effects following GUM principles. The proposed methodology provides an uncertainty-qualified and measurement-oriented framework for discriminating stable and unstable FSW operating regimes.
Source: Measurement
Institutions: University of Naples Federico II, Mercatorum University
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,760
OpenAlex ID: W7148569086