T尾结构振动的模态局部化判据研究

MODE LOCALIZATION PREDICTION CRITERION FOR T-TAIL STRUCTURE

用峰值振幅比定义局部化度,用平尾刚度与垂尾刚度的比值定义耦合度.基于T尾结构的质量失调模型,从模态峰值振幅比、失调耦合比、常规摄动和近频摄动4个角度,提出4个不同的局部化判据来预测T尾结构模态局部化的发生.对一个T尾结构模型局部化振动的数值分析结果表明:(1)T尾结构系统一般具有弱耦合性,小量的失调就可以使T尾结构发生模态局部化;(2)T尾结构一旦发生模态局部化,不但使对称一弯模态和反对称一弯模态的振型发生较大改变,而且其模态频率也将改变,模态频率的改变在失调量的正负区间内具有唯一性;(3)算例验证了4个模态局部化判据的可行性和有效性,为T尾结构的模态局部化分析和设计提供了依据.

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.