Model Validation And Application Usingradial-tchebichef Moment Function In Structural Dynamics

Model validation enables the discrepancy between the prediction result of FE model and the test within the acceptable limits including the processes of model verification, correlation analysis and model updating. The FE model confirmed by the process of model validation can be used to represent the dynamic property of the actural structure and to predict the structure’s dynamic response.With the development of the test technology, such as the laser Doppler velocity(LDV), the full field experiment vibration data can be obtained. It faces many problems when using traditional methods of correlation analysis and model updating to handle the larege amount vibration data. In addition, the traditional correlation analysis method can’t describe the double modes of symmetrical structure. A new method based on Radial-Tchebichef moments which is used in the image processing is proposed for correlation analysis and model updating.Firstly, the descripton of mode shapes based on Radial-Tchebichef moments are studied and compared the result with Zernike moments. Then, the Radial-Tchebichef moments are used to describe the three-dimensional strcture by projecting the three-dimensional structure into two-dimensional strcture. With this method, a good result of image reconstruction for three-dimensional structure is gained. Secondly, the concept of Radial-Tchebichef polynomial is proposed and its orthogonality is also proved. The basic moment shapes are then plotted out at the first time. This method is used to extract the shape feature and reconstruct the image of one vibration mode shape of a disk. A good reconstruction result is gained using only three basic moment shapes and Radial-Tchebichef moments. In addition, the Radial-Tchebichef moments are used to recognition the position of an added mass in a disk and obtain the result with good identification accuracy. It has important significance for the development of damage identification using Radial-Tchebichef moments. Finally, Radial-Tchebichef moments are applied to the correlation analysis and model updating. Taking a disk as example, through the analysis of the test and FE model, the result shows that the double modes can be effectively described and the angles of the double modes can be computed by Radial-Tchebichef moments. So this method can overcome the disadvantages of MAC. Furthermore, using Radial-Tchebichef moments in model updating, taking the cover of an aero engine test rig as an example, the result shows that the frequency deviation between the test and FE model is reduced from 17.13% to 1.23% after model updating in the first 13 modes and this case verifies the effectiveness of the proposed method.