Model Validation And Application Using 3-Dimensional Radial Axial Tchebichef Moment Function In Structural Dynamics

The development and application of non-contacted vibration measurement technology,achieve more precise and large amount of data of the global mode becomes the truth.Meanwhile,it put forward higher requirements for data processing.Dealing with such data,the traditional modal analysis and model updating method has some limitations,and correlation analysis of axisymmetric structures,analysis of the deficiencies of traditional mode of double which can not be accurately described.In this paper,the theory of moment functions in image processing is applied to the description of the modal shapes of axisymmetric structures.In this paper,we focus on the improvement of axial polynomial of moment function RAT(Radial Axial Tchebichef)polynomial function,and realize the data processing of the RAT moment to the complex structure.The method is to improve the actual structure of the axial approximation polynomial,polynomial fitting complex rotation surface structure,based on the Tchebichef polynomial approximation to construct the axial polynomial.The improved RAT moments are used to compress and reconstruct the mode shapes of the axial complex structures(such as the conical casing).The method of model validation based on improved RAT moment function is also studied.The main work of this paper includes:Firstly,using the axial moment function of polynomial 3D RAT moments,to improve axial polynomial,and prove the orthogonality and rotation invariance of RAT moment function of the integral kernel polynomial of the improved modal reconstruction formula is derived.Secondly,the feasibility of the method of describing the modal shape of the improved RAT moment function is verified.The improved RAT moments can be used to directly extract the characteristic mode set of modal shapes of complex structures,such as conical shells.In addition,the improved RAT moment function is used to reconstruct the modal shape of the conical shell with random noise,and it is verified that the model based on the RAT moment function is also robust.Finally,the method of structural dynamic model identification based on improved RAT moment function is studied.In this paper,based on the dynamic characteristics of the engine,the simplified model of the combustion chamber and the modal shape of the finite element model are established by using the improved RAT moment.According to the improved RAT moment function,the matching of the mode and the angle between the modes can be realized.In addition,the model updating method based on the improved RAT moment function is used to model the finite element model of the combustion chamber.The results show that considering the modal frequency and RAT moment model can make the correction results converge,to avoid divergence or oscillation,greatly reduce the frequency difference,verify the correctness and feasibility of the improved method of moments RAT.