空间框架结构扭转参数共振试验现象和机理

Experimental Phenomenon and Mechanism of Torsional Parametric Resonance of a Spatial Frame Structure

扭转参数共振现象在已有的结构参数共振试验中尚未观察到,针对此问题,通过试验手段对一个空间框架模型的扭转参数共振问题进行研究。采用不接触的电磁激励方法,激发空间框架结构模型的扭转参数共振,对空间框架扭转参数共振现象和机理进行观测和分析,研究了结构扭转参数共振的稳定性问题以及参数共振下稳态激励幅值与非线性响应幅值的变化关系。试验结果表明:当外部周期激励的频率大约为2倍的结构扭转自振频率时,空间结构将发生整体扭转参数共振;扭转参数共振稳定边界与已有其他结构平动参数共振的稳定边界相似,扭转参数共振的机制与平动参数共振基本相同;在不稳定区域内,当固定激励频率时,随着激励幅值的增大,非线性稳态响应的幅值近似地呈线性增大。

The phenomenon of torsional parameter resonance has not been observed in existing structural parametric resonance experiments.In this paper,a careful experimental study on the torsional parametric resonance(dynamic instability)is firstly conducted for a spatial frame model.A novel non-contact electromagnetic excitation method is used to excite the torsional parametric resonance of the spatial frame model.The phenomenon and mechanism of torsional parametric resonance of the spatial frame are observed and analyzed.The stability boundary of the structural parametric resonance is measured and explored.Moreover,the variation relationship of the steady-state excitation amplitudes and the nonlinear(steady-state)response amplitudes is investigated in the unstable domain.The experimental results show that when the frequency of external periodic excitation is about twice the torsional natural frequency of the structure,the global torsional parametric resonance occurs in the spatial structure.The stability boundary of the parametric resonance is similar to that of the existing translational parametric resonances of other frame structures.The mechanism of the torsional parametric resonance is essentially the same as that of the translational parametric resonance.In the unstable region,when the excitation frequency is fixed,the amplitudes of the nonlinear steady-state response increase approximately linearly with the increase of the excitation amplitudes.