Vibrations of joined conical-cylindrical shells with bolt connections: Theory and experiment

This paper investigated the vibration characteristics of joined conical-cylindrical shells (JCCSs) with bolt loosening boundary conditions both theoretically and experimentally. The non-uniform arc constraint model is established to simulate the bolt loosening boundary conditions by the artificial spring technology, which can describe the actual bolt contact pressure distribution. Continuously distributed artificial springs are introduced to realize the connection of the conical and cylindrical shells. Donnell's shell theory and Chebyshev polynomials are adopted to establish the theoretical model, and the dynamic equation is derived from the Lagrange equation. The validity of the present model is verified by the available literature, hammer test and vibration shaker test. The results indicate that the maximum errors of natural frequencies and resonant displacements are less than 4.41% and 18.6%, respectively. It is found that bolt loosening has a significant effect on the fundamental frequency, but it gradually weakens with the increase of the mode order. Increasing bolt loosening degree can lead to an increment of resonant displacement. The developed model is reliable in estimating the dynamic behaviors of bolted JCCSs with different loosening degrees, and it contributes to providing guidance in the design and service process of combined shell structures.