Abstract
The analysis of the structural dynamic behaviour of composite rotor–discs by a valid description of the eigenfrequencies and mode shapes can provide significant information for action-taking before a failure occurs. Specifically, vibration-based diagnostic methods, which are able to take into consideration the interdependencies and sequential changes of the modal properties could benefit from such an analysis. Here, on the example of composite rotors, a correlation method for experimentally determined mode shapes is developed. For this purpose the Zernike polynomials are used to enhance the identification of mode shapes. Furthermore, the modal assurance criterion (MAC) in combination with the frequency response criterion and a data processing approach are applied in order to characterize changing modal properties of composite rotors. In addition, the developed algorithms can be further extended in order to simplify the experimental evaluation of the complex dynamic behaviour of composite structures.
Highlights
An unknown or a false understanding and subsequent description of the structural dynamic behaviour of composite rotors can lead to severe misinterpretations and false decision making.Especially in damage identification methods such as vibration-based diagnostics, a false classification of the vibration response to a damage state can result in a catastrophic failure
To evaluate the developed approach, the correlation method was applied to experimental data gathered from glass fibre reinforced rotors using experimental modal analysis [23]
The investigated rotors consisted of preform and were fabricated using the tailored fibre placement (TFP) process [24]
Summary
An unknown or a false understanding and subsequent description of the structural dynamic behaviour of composite rotors can lead to severe misinterpretations and false decision making. The goal of the current investigation is to gain information and knowledge regarding changes of the structural dynamic behaviour of composite rotors by developing a correlation method that is able to automatically identify the eigenfrequencies and the resulting mode shapes. To characterize changing modal properties the ZERNIKE polynomials and the modal assurance criterion (MAC) in combination with the frequency response criterion are applied. This method has been developed primarily to be used with circular symmetric structures, which allows us to define assumptions by which certain mode shapes can be associated to each other or excluded. Symmetric rotor structures with isotropic or polar orthotropic material behaviour, which correspond to those of a circular membrane, show such features
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