Research on the distorted similitude of bolt-connected coupled cylindrical-conical shells

Abstract

The model similitude technique, which employs scaled-down models to reflect the dynamic characteristics of full-scale models, has garnered significant attention in the engineering field. The inability to establish geometrically scaled models due to excessively thin shell structures has led to similitude distortion. For bolt-connected coupled cylindrical-conical shells, the dimensions of bolts (connection stiffness) vary with the radial dimension of the structure, and the coupling effects between parameters further complicate the establishment of scaling laws. To address these challenges, the distorted similitude method based on bolt equivalent stiffness modeling is proposed. For the first four bending mode natural frequencies, distorted scaling laws for the length, radius, and their coupling under double distorted reduction are established. The theoretical prediction errors of these scaling laws for the prototype are found to be within 5.43 %, 2.31 %, and 1.12 %, respectively. Experimental results demonstrate that the prediction error of the coupled distorted scaling law for length and radius is within 5.37 %. In cases of small radii, large thicknesses, and long axial lengths of bolted joint shell structures, the distortion of bolt dimensions due to radial distortion cannot be overlooked. Moreover, if the bolted joint is located at the vibration mode node, the corresponding scaling law can disregard the influence of connection stiffness. This study realizes the establishment of distorted models for complex bolted joint shell structures and enhances the prediction accuracy of coupled scaling laws, thus holding significant engineering application value.