Modal identification of double-layer hollow stiffened plate structure using variational mode decomposition based on high-speed digital image correlation

The purpose of this study is to verify the applicability of the proposed non-contact optical vibration measurement techniques to identify modal parameters and the stiffness enhancement effect of the designed new stiffened plate structure. A thin-wall structure can bear a large load with less weight and fewer materials, which has attracted more and more attention in the field of aerospace, but its use is limited by its weak rigidity. Therefore, we proposed a double-layer hollow stiffened plate structure manufactured by a superplastic diffusion bonding process. We verified by the finite element method that the first-order natural frequency of the system with the same size and mass increased from 5.8742 to 61.2224 Hz. In addition, digital image correlation technology, laser Doppler vibrometer, and accelerometer were used to measure the vibration of stiffened plate structure in free state at room temperature. The three vibration testing methods agree with finite element analysis's first six modal parameters. The variational mode decomposition (VMD) algorithm was used to identify the modal parameters of three kinds of vibration test response data of double-layer hollow stiffened plate structure. The results show that the method is effective and has good identification accuracy for the dense modal of the system. The proposed VMD method can provide effectively modal parameter identification of vibrating structures in practical application.