Modal Parameter Identification And Software Of Thin-walled Cylindrical Shell

Shell structures have a very good carrying capacity and is adapted to the structure of light and weight as well as sufficient strength and stiffness, they are widely used in the fields of aerospace, aviation, oil and pipeline, construction machinery and others. Therefore, their dynamic problems have become the keys for many engineering structural design and researches.In this paper, the focus of this study is on modal parameter identification method of thin-walled cylindrical shell and corresponding software development, which researches the modal parameter identification method of thin-walled cylindrical shell systematically. The main research contents of this paper are as following:(1) Taking full account of thin-walled cylindrical shell test requirements, reasonably equipping hardware test system of thin-walled cylindrical shell vibration. And the description of the development process and the use of the process is showed in details, and the effectiveness of the software verification is showed.(2) The support software of thin-walled cylindrical shell test method is developed. Firstly the test method of thin-walled cylindrical shell modal parameters are summarized, including natural frequencies, damping ratios and mode shapes, and secondly the support software of thin-walled cylindrical shell test method is developed by using VB software platform through the interface way. The detailed description of the development process and the use of the process is showed in details.(3) In order to make modal parameter identification better, the vibration signal pre-processing software is developed, specifically including: elimination of polynomial trend term and smoothing. In this paper, the method of least squares polynomial trend is used to eliminate items, and the average method is used to smooth data. Through the data pre-processing, the vibration signal preprocessing is carried out under the maximum measured signal so as to remove high frequency noise. In addition, digital filtering software of the frequency domain approach is also developed.(4) According to the experimental modal theory, the modal parameter identification software of thin-walled cylindrical shell is developed based on Matlab software platform, including natural frequency, damping ratio and mode shapes identification. The description of the software development process identification is showed in detail, the experiments of thin-walled cylindrical shell are carried out under free-state and constraint-state respectively in order to verify the effectiveness of the program.