To accurately predict the free vibration characteristics of bolted joined cylindrical shells, discontinuous variable-stiffness artificial spring is proposed to simulate the boundary conditions of bolted joined cylindrical shells in this paper. The artificial spring is distributed only in the influence zone of bolted connections, and the spring stiffness is variable to simulate the inconsistency of the contact pressure in the influence zone. Characteristic orthogonal polynomials with good accuracy and convergence are utilized to characterize the displacement of the cylindrical shell. The dynamic equations of the cylindrical shell are established by using Sanders’ shell theory and Lagrange equations. Moreover, finite element analysis (FEA) is conducted to verify the presented model. And an actual bolted joined cylindrical shell is chosen to perform modal tests. According to the test results and the dynamic model in this paper, the particle swarm optimization algorithm (PSO) is employed to determine the stiffness of the artificial spring. Based on the identification results and proposed model, the natural frequencies and modal shapes of bolted joined cylindrical shells were obtained and compared with the test results. The comparison results indicate that the model in this paper can accurately predict the free vibration characteristics of bolted joined cylindrical shells.
 

Free vibration; bolted joined cylindrical shells; discontinuous variable-stiffness spring; particle swarm algorithm; modal test