Transmissibility Based Operational Modal Analysis And Software Implementation

With the development of science and technology, various structure dynamics problems are becoming prominent. Modal analysis is applied to the fields of aerospace engineering, engineering machinery, engineering machinery, civil engineering, rail transportation. It has become a powerful tool to solve these problems. Compared with the traditional experimental modal analysis, operational modal analysis technique has the advantages of having good security, taking low testing cost and free of affection to the normal work of the structure and other advantages, which has become a research hotspot in the field of modal analysis.The techniques of transmissibility based operational modal analysis is systematically studied in this thesis. First of all, the common frequency response function estimation methods are introduced into the transmissibility function estimation. Five transmissibility function estimation methods are studied. The estimation errors of different algorithms are compared by a simulation example, and the results show that the vH estimation method is the best algorithm. Rational functions are constructed by combining transmissibility measurements under two different loading conditions. The rational fraction orthogonal polynomials method and least squares complex frequency domain method are studied to fit the rational functions. A simulation example of two-DOF bending and torsion wing model and an experiment of a cantilever beam are used to validate the approaches. Good result are achieved by using this technique, even if the excitation is not white noise. The transmissibility function is estimated by measuring the acceleration signal of the foundation and structural response. A transmissibility based modal analysis method for base excitation is presented. A simulation example of a five-degrees-of-freedom and an experiment of an aluminum plate are used to validate the approach. Based on MATLAB GUI programming technique, modal analysis software with good human-computer interaction is developed for the modal parameter identification, which is helpful to the further research and engineering application of research achievements.