Damage can be identified using generalized flexibility matrix based methods, by using the first natural frequency and the corresponding mode shape. However, the first mode is not always appropriate to be used in damage detection. The contact interface of rod-fastened-rotor may be partially separated under bending moment which decreases the flexural stiffness of the rotor. The bending moment on the interface varies as rotating speed changes, so that the first- and second-modal parameters obtained are corresponding to different damage scenarios. In this paper, a structural damage detection method requiring single nonfirst mode is proposed. Firstly, the system is updated via restricting the first few mode shapes. The mass matrix, stiffness matrix, and modal parameters of the updated system are derived. Then, the generalized flexibility matrix of the updated system is obtained, and its changes and sensitivity to damage are derived. The changes and sensitivity are used to calculate the location and severity of damage. Finally, this method is tested through numerical means on a cantilever beam and a rod-fastened-rotor with different damage scenarios when only the second mode is available. The results indicate that the proposed method can effectively identify single, double, and multiple damage using single nonfirst mode.

No abstract

No abstract

A reduced mesh movement method based on pseudo elastic solid is developed and applied in fluid–structure interaction problems in this paper. The flow mesh domain is assumed to be a pseudo elastic solid. The vibration equation for the structure and the pseudo elastic solid together is derived by applying the displacement continuity condition on the fluid–structure interface. Considering that the actual fluid–structure coupled vibration for structures often appears to be associated with low-order modes, the nodal displacements for the structure and the flow mesh can be computed using the modal superposition of a few low-order modes. Coupled fluid–structure computations are performed for flutter problems of a beam and wing 445.6 using the present method. The calculated results are consistent with the data reported in other references. The computing time is reduced by 65.5% for the beam flutter and 54.8% for the wing flutter compared with the pre-existing elastic solid method.

In this paper, a modal approach for the fast calculation of flow mesh deformation around a wing is developed based on the elastic solid method of dynamic mesh. The flow mesh domain is assumed to be a pseudo elastic solid. The displacement of the wing and the pseudo elastic solid is continuous at the fluid structure interface. Considering the condition of displacement continuity, the governing equation for the vibration of the wing with the pseudo elastic solid together is derived. The frequencies and mode shapes of the wing and the pseudo elastic solid are computed. Then the nodal displacements for the wing and the flow mesh are computed using modal superposition. The flutter boundary of the AGARD Wing 445.6 is predicted using the present modal approach by considering the first four modes of the wing. The calculated results compare well with the experimental data. The computing time is reduced by 54.8% compared with the pre-existing elastic solid method.