Rigid-flexible coupling dynamic analysis of a rotating flexible beam with cracks

The effect of a crack on the dynamic behaviors of a rotating flexible beam system with rigid-flexible coupling effect is investigated through the application of a lattice spring model (LSM). Based on the local flexibility theory of cracks, the flexural stiffness of the cracked section is represented by a massless rotational spring, and then the first-order approximate coupling model of the rotating flexible beam is established, which takes account of the nonlinear coupling between transverse and longitudinal deformations. Numerical results show that the presence of the crack lowers the natural frequencies of the rotating flexible beam, and as the rotation speed of beam increases, the impact of the crack on the natural frequencies becomes weakens. In particular, a positive correlation between the natural frequencies and the bending moment at the crack is discovered. In addition, the crack can not only increase the response at the beam tip during the stage of rotation speed increase, but also has a significant impact on its oscillation amplitude during stable rotation.