Modal Analysis Using Digital Image Correlation Technique: An Application to Artificial Wing Mimicking Beetle’s Hind Wing

Abstract

Understanding the dynamic behavior of structures has become increasingly important in the design process of any mechanical system. Therefore, the demands for improved structural performance have motivated the search for an effective method of structural dynamics testing, since the conventional methods are limited to the location of relatively few applied sensors. Due to the state-of-the-art optical technologies, the shape and deformation of a vibrating structure have been measured using 3-dimensional digital image correlation (DIC) technique. Although DIC has been used widely to construct the mode shape of the structure in modal measurement, it has rarely been applied to determine the full modal parameters (natural frequencies, mode shapes, damping factors). Therefore, this study presents an effective method to measure the full modal parameters of an artificial wing that mimics a beetle’s hind wing using the DIC technique. In our measurement, the artificial wing was mounted on a shaker, which was vibrated with a white noise signal. The full-field result as well as the displacement of a single point on the wing over time was then obtained using ARAMIS® software, a DIC technique-based software. From the temporal displacement of a single point signal in the time domain, we performed fast Fourier transform to obtain the frequency response function (FRF). The spectrum averaging technique and Savitzky-Golay filter were used to reduce the noise. Also, the natural frequencies and damping factors were determined from smoothed FRF. Finally, the mode shapes were measured using DIC at the pre-measured natural frequency.