Thermoelasticity-based stress mode-shape identification in rotating structures

In experimental modal analysis of rotating structures, optical methods provide full-field and non-contact alternatives to traditional sensors. Thermoelastic stress analysis was recently related to experimental modal analysis and shown to offer a non-contact, full-field approach for stress mode shape measurement by capturing minute (typically below 1 mK) surface temperature fluctuations associated with dynamic loading. However, applying thermoelasticity to large-scale moving structures remains challenging due to motion artifacts and the need for reliable tracking of surface points to preserve spatial alignment across frames. This study introduces infrared ArUco markers to track the rigid in-plane motion of a rotating aluminum beam undergoing out-of-plane vibration during thermoelastic measurements. Frame-to-frame transformations are applied to de-rotate the thermal video, enabling accurate modal parameters and full-field mode shapes identification. An uncertainty analysis is performed to assess the impact of motion compensation, revealing sub-pixel transformation errors across diverse experimental scenarios. By extending thermoelasticity-based stress modal shape measurements to rotating structures, the introduced method enables a non-contact stress measurements in dynamic environments, opening new opportunities for structural health monitoring and fatigue assessment of rotating components. • Infrared ArUco markers are introduced to track in-plane motion. • Sub-pixel motion accuracy is achieved across various operating conditions. • Stress mode-shapes of rotating structures are identified via thermoelastic method.