弹性边界试验获取自由状态频响方法研究

Extraction of free body frequency response functions from elastically constrained test

大型柔性航天结构的一阶频率可能低至0.1 Hz,采用自由悬吊方法进行结构自由状态频响测试难以满足要求,因为它要求悬吊频率远低于待测结构的一阶频率。为解决这一问题,文章研究了弹性边界试验方法:对待测结构施加弹性支撑,在分别获得整体与支撑结构频响后,通过频域子结构解耦方法,去除支撑结构对待测结构的影响,以得到待测结构自由状态的频响。试验结果表明,这一方法是可行的,可以考虑进一步应用于实际工程结构。

A large scale structure might have a very low first natural frequency,as low as 0.1 Hz.Traditionally,the method of the low stiffness suspension is a standard method for the modal test of structures.A requirement on the suspension stiffness is that the suspension frequency should be much lower than the first flexible natural frequency of the tested structure.For the large scale structure,a very long suspension spring is required to achieve the required frequency.This low frequency requirement might not be able to be met in many labs.In this paper,a method is proposed to deal with the above problem by replacing the low stiffness suspension with a group of supports that can have any stiffness.By removing the influence of the support stiffness from the computation with the measured frequency responses,the structure’s real modal parameters can be obtained conveniently.Experimental examples are given.