Research On Error Localization Methods For Thin-Structures Modeling Considering Rotational Degree Of Freedom

The aero-engine is complex,in order to improve the calculation efficiency,2D shell element is often used in the engine casing dynamic modeling to reduce the system’s degree of freedom.Due to the inevitability of structural simplification,discretization and inaccurate parameters in the process of modeling,there is some difference between the predicted results of FE(finite element)model and the actual structure.In order to reduce the error of FE model,the technology of model modification and validation came into being.Reasonable parameter selection is the key of model updating.The parameter with error must be identified in order to ensure that the results have right physical significance.In order to identify the error parameters of thin-walled structures in the process of model updating,this paper develops an error identification method based on EMSE(element modal strain energy).At the same time,because the RDOF(rotational degree of freedom)is very important for the element modal strain energy calculation,a method for RDOF measurement is proposed based on the difference method.Firstly,the principle of error source identification based on EMSE is expounded,and a stiffness error indicator is established based on EMSE.The error indicator is verified by beam simulation.In addition,the necessity of RDOF in modal strain energy calculation is discussed.Ignoring the RDOF will lead to the failure of error identification.In order to measure the RDOF,three Doppler laser synchronous sensors are used to measure RDOF and TDOF(translational degree of freedom)FRF(frequency response functions)based on the difference method,and the simulation and experimental verification are carried out on the plate.Then,the plate 2D design model error is identified by the stiffness error indicator with the 3D FE model and the test data as reference.The results show that the indicator can locate the stiffness error element of the design model when the FE model is used as reference.When test data is used as reference,the RDOF measurement is not ideal,which leads to the failure of low order indicators.Error element can be located by normalized higher order indicator.Finally,the error identification method is applied to the thin-casing,and the FE model stiffness error is identified by referring to the RDOF and TDOF obtained from the modal test.In this paper,the research and implementation of RDOF measurement have solved the technical problems in modal testing.FE model error identification based on EMSE Referring to the test data promotes the application and development of error identification technology in practical engineering.