Mode localization prediction criterion for T-Tail structure

Mode localization is often an unexpected dynamic phenomenon in weakly-coupled symmetric structure, and it arises from small imperfections (less than 5%) which perturb the symmetry. Such imperfections typically result from random manufacturing or assembly imprecision. Mode localization prediction is an important problem in T-Tail structure design because some drastic localized vibration phenomena occur during ground vibration test of T-Tail aircraft. Mode localization is dependent not only on mistuning, but also on coupling intensity. In this paper, we define the degree of mode localization with the peak amplitude ratio and the coupling intensity with stiffness ratio of horizontal stabilizer to fin in T-Tail structure. The influence of mass mistuning on mode localization and frequency loci veering of T-Tail structure is studied. Based on the mass mistuning model, four different criterions are proposed to predict the occurrence of mode localization in T-Tail structure from four view points, which are the peak amplitude ratio, coupling mistuned ratio, ordinary eigenvalue perturbation method and eigenvalue perturbation method for nearly equal frequencies, respectively. The numerical simulation results for a T-Tail structure model indicate that mode localization is most likely to occur in T-Tail structure consisting of weakly coupled substructures-horizontal stabilizer and fin. Moreover, when localization occurs, the first two bending vibration modes in T-Tail structure are prone to localization, and only one of the two mode frequencies is changed by parameter mistuning to induce frequency loci veering phenomena. The results of this study also demonstrate the feasibility and effectiveness of the proposed four predicting criterions of mode localization, and thus provide a reference solution to the prediction and design of mode localization of this kind structure.