Research On Error Localization Methods For Model Updating Of Aero-engine Casings

As the discretization and simplification of the actual model, the created finite element model is always discrepant from the actual one because that there are some uncertainties in the modeling process. It's very important to evaluate and update the design finite element model by model updating and validation. Updating parameter selection is a critical step in the model updating and validation process, which makes the updating results more meaningful, but the biggest challenge is how to localize the errors in the finite element model. As the skeleton of an aero-engine, vibration of casing structures directly reflects the vibration of the machine. In this paper, taking an aero-engine casing as the a research object, some steps have been studied in the framework of model updating and validation such as modeling, modal test, correlation, error localization and updating. Accordingly, a method for error localization of design models based on equivalent element modal energy is innovatively investigated in this paper and applied to model updating process.Firstly, the overall framework of structural dynamic model validation is introduced. The significance of error localization among model validation process is also described. Besides, a method to localize errors based on Equivalent Element Modal Strain\ Kinetic Energy is proposed.Then, the effectiveness of the proposed method and indicators' influences are demonstrated by the simulation research on Euler-Bernoulli beam structures and plate structures. Next, for the condition of error localization for beam models via reference data obtained from modal test, one step of calculating modal rotation using known modal displacement needs to be added to improve the original method. The advantages and disadvantages of the error localization method based on modal test data are also discussed in the engineering application.Finally, the proposed error localization method is applied in 3D solid casing structures, taking a cylinder casing and an actual aero-engine combustion chamber casing as examples. It can be known that more accurate error localization results must be gained when there is a high correlation between the design model and reference model by the simulation and verification of the cylinder casing. In order to localize errors in the design model of the combustion chamber casing, the method via supermodel is used to ensure the integrity of reference data. A general process of model parameters selection is established to guide the model updating process. With this method, the model updating results have more physical meanings, which is to say the updated finite element model can more accurately describe the dynamic characteristics of a structure.