Rotating machinery plays an essential role in aerospace, energy, automotive, and other industries. A resonance phenomenon will occur if the rotational speed of the structure is close to its critical speed. Experimental analysis of the modal shapes of a rotating component at critical speeds can improve its design and performance in applications. Full-field deformation measurements of a rotating structure can be realized by three-dimension digital image correlation(3D-DIC) based on high-speed cameras. However, high-speed cameras are too expensive to apply widely. This study presents a method using 3D-DIC and a down-sampling strategy, which only uses low-cost normal-speed cameras. In order to ensure that two low-speed cameras can synchronously capture images clearly, a synchronous stroboscopic device is used. A measurement experiment was executed on a rotating disc at a critical speed to verify the availability of the method. The experiments show that the out-of-plane displacement of a rotating disc at different critical speeds corresponds to the various orders of modal shape. Compared with the non-resonance state, the out-of-plane deformation of the rotating disc was significant. The results also show the proposed method is a low-cost, non-contact experimental tool to study the dynamic behavior of a rotating component.
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