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中文核心期刊

基于子结构解耦的连接特性识别新方法

A NEW METHOD OF JOINT DYNAMIC PROPERTIES IDENTIFICATION USING SUBSTRUCTURE DECOUPLING

  • 摘要: 连接部件动态特性的准确辨识对预测装配式机械结构的动力学行为有重要意义. 针对传统基于子结构解耦的连接结构动力学特性识别方法难以直接利用可测量数据进行辨识及辨识结果受噪声影响显著等问题, 本文提出了一种新方法. 首先, 提取子结构解耦基本方程在测试自由度上的分量, 并经矩阵变换得到显含连接动刚度矩阵的形式, 而后由真实连接动刚度矩阵分解为已知的初始矩阵与待求的增量矩阵, 推导了具有收敛性质的增量型方程以增强界面自由度较多时辨识的数值稳定性, 并采用多项式拟合动刚度将其转化为了拟合系数的频域估计方程, 按给定准则选取合适的频率点联立方程后, 得到了只需装配体测试自由度上的频响函数来辨识连接特性的迭代公式. 最后, 以若干算例说明了算法的具体流程. 对10自由度弹簧−质量块系统进行了数值仿真, 验证了所提方法的正确性及抗噪性; 对包含一处胶接连接的T形梁结构和包含两处螺栓连接的L形梁结构进行了试验, 所辨识连接结构与残余结构重组的装配体有限元模型计算的频响函数与测量值在较宽频带内吻合较好, 表明了该方法能有效识别实际装配体结构中的连接特性.

     

    Abstract: Identification of mechanical connections plays a significant role in predicting the dynamic behavior of an assembled structure. Due to the noise affection and the difficulty to directly use the measurable data to identify the dynamic properties of the joint with traditional methods based on substructure decoupling, a new method is proposed. Firstly, the components of the basic equation of substructure decoupling on the measurement degree of freedoms (DOFs) are extracted, and the form containing the joint dynamic stiffness matrix is obtained by matrix transformation. Then, the real joint dynamic stiffness matrix is decomposed into a known initial matrix and an incremental matrix to be solved, and the incremental iterative equation with convergence property is derived to enhance the numerical stability of identification when the number of interface DOFs is extremely large. Polynomial fitted dynamic stiffness is used to form a frequency domain estimation equation of fitting coefficients representing joint properties. By selecting appropriate frequency points to simultaneous equations according to the given criteria, an iterative formula for identifying joint properties is obtained, in which only the measurement frequency response functions (FRFs) of the assembly are needed. Finally, a numerical example and an experimental example are provided to verify the method and to describe the identification procedure. Numerical simulation of a 10-DOFs spring-mass system verifies the correctness and anti-noise of the proposed method. Tests and identifications are also carried out on a T-shaped beam structure with one adhesive connection and a L-shaped beam structure with two bolted connections. The result shows that the FRFs calculated by the finite element model (FEM) of the assembly recombination by the residual structure and the identified joint is in good agreement with the measured values in a wide frequency band, which indicates the effectiveness of this method in identifying the joint properties in the actual assembly structure.

     

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