一种基于摄动力的不完备模态扩充方法

Incomplete Modal Expansion Method Using Perturbed Force

通常,应用损伤标识量进行损伤识别时都需要用到结构的完备模态,而实际振动试验难以测得结构的全部自由度信息。已有的模态扩充方法大都没有考虑有限元模型与试验模型之间的模型误差。基于摄动力矢量的模态扩充方法,考虑了刚度摄动对摄动力的影响。同时,考虑到有限元模型与试验模型之间的误差,引入模态修正因子。然后,通过模态置信准则对该方法进行评估。最后,以空间桁架结构模型进行数值分析,表明该方法扩充后的模态相关性较好,各阶模态误差较小。

The measured modals are incomplete in practice because of the limited number of sensors,and the rotational degrees of freedom are usually difficult to measure. To deal with the incompleteness of measured modal data for the damage identification of structure, a new mode shape expansion methods is presented. The approach adopts a perturbed force vector which can be obtained from measured modal data and only consider the influence of stiffness perturbation. Modelling-difference between the finite element analysis model and the actual tested model were also considered by introducing a set of model correction factors. And modal assurance criterion（MAC） was used to evaluate the performance of the existing meth-ods and proposed method. Finally,the proposed method was numerically illustrated by a spatial truss mo-del. Results indicated that the unmeasured components in the modal shapes were properly estimated by implementing the proposed method.