复合材料杆件模态参数的识别研究

Investigation on the Modal Parameter Identification of a Composite Bar

基于杆件纵向振动理论,推导了复合材料杆试件的机械阻抗解析公式,并用瑞利法计算了无阻尼离散系统的模态质量和基频。在机械阻抗平台上,采用单点激振法进行实验,得到频域内复合材料杆件的机械阻抗数据。用实验方法、解析方法和混合方法进行了模态参数的初步识别。然后,用非线性最小二乘方法中的Levenberg-Marquardt算法求得了模态参数的最优值。研究结果显示:采用优化参数的单自由度离散系统模型与实验结果吻合良好,在实验频段可以较好地描述复合材料试件的动力学特性。

The mechanical impedance formulae of a composite bar are deduced according to the longitudinal vibration theory in this paper, and the modal mass and the fundamental frequency are estimated by Rayleigh method.The composite bar is tested on the impedance platform facility with single point excitation and the mechanical impedance data are obtained.The initial modal parameters are then identified with the experimental approach,theoretical approach and hybrid approach.After these,the optimal modal parameters are identified by nonlinear least square method called Levenberg-Marquardt algorithm.Research work shows that the single degree of freedom discrete system model using the optimal modal parameters coincides with the experimen- tal data very well,and it can well describe the dynamic properties of the composite bar in the frequency range of test.