铰接式空间桁架结构模态试验研究

铰接式空间桁架结构铰链多、柔性大,其地面环境下的动力学特性较难准确获取。桁架结构地面模态试验易受试验条件的影响。采用锤击法对桁架结构进行模态试验,获得了桁架结构的模态参数,并通过模态置信准则验证了试验结果的可靠性。结合不同试验工况,分析了悬挂条件和拾振点位置对桁架结构模态试验结果的影响。建立了桁架结构有限元模型并进行模态分析,与试验结果进行对比。试验结果表明:降低悬挂附加刚度有利于避免模态耦合;悬挂点均匀对称布置可减轻铰链滑移对结构整体刚度的削弱,提高试验的可重复性;拾振点居中布置有利于提高辨识模态的完备性;增加悬挂长度可降低悬挂效应对低阶模态的影响。研究结果对大型含铰柔性结构的地面模态试验具有借鉴意义。

Modal experiment for a spherical hinged space truss structure

The accurate dynamics characteristics of a flexible and joint-dominated space truss structure is difficult to obtain in the ground test.The ground modal test of truss structure is susceptible to test conditions.The experimental modal analysis of a spherical hinged space truss was conducted using the hammer method.The modal parameters were obtained based on the experiment results.The MAC (Modal Assurance Criterion) was utilized to verify the reliability of the results.Combined with different cases in the test, the influence of suspension condition and response point position on the modal experimental results of the truss structure was analyzed.The modal analysis of the truss structure under free boundary condition was carried out using FEM.The results obtained through the experiment method and FEM were compared.The results show that lower added stiffness of suspension can avoid modal coupling.distributing suspension points uniformly and symmetrically improves the repeatability of the modal experiment.placing accelerometer near the center of the structure reduces the energy loss of the excitation, which can ensure the completeness of the modal results.increasing length of suspension can reduce the influence of suspension effect on low order modes.