A low-speed camera DIC approach for measuring synchronous vibrations in rotating disks

During operation, turbomachinery blades are subjected to dynamic excitations, which are the primary drivers of high-cycle fatigue, the leading cause of failure in bladed disks. Therefore, accurate measurement of their dynamic response under resonance is critical for reliable design. Traditional contact-based measurement techniques suffer from drawbacks such as added mass, limited lifespan, and complex data transmission, prompting interest in non-contact alternatives. This paper explores the application of digital image correlation (DIC) for analyzing synchronous vibrations in bladed disks. The proposed approach employs low-speed, high-resolution cameras combined with downsampling strategies to enable cost-effective, full-field, high-resolution measurements. A signal processing technique, the circumferential harmonic fit (CHF), is proposed and applied to extract system parameters from downsampled displacement data. The methodology is applied on a simplified bladed disk mounted on a spinning rig, demonstrating successful identification of operational deflection shapes at resonance.