Experimental Modal Analysis of Business Jet Fuselage Tail Section Sub-Assemblies
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Experimental modal testing is a technique through which the dynamic response characteristics of a system can be found. Parameters such as the natural frequencies and mode shapes of a system can be extracted through experimentation, and these results can be used to confirm computational models, and/or provide insights from which improvements can be made to improve dynamic response characteristics. This thesis provides an overview of experimental modal analysis performed on two half scale aircraft fuselage subassemblies using shaker excitation. Prior to experimentation, relevant literature was reviewed. This provided the necessary foundation of theory and prior experiments which helped to form the experimental methodology presented. This methodology including the construction of each structure, data acquisition parameters, and validity checks, is covered in detail. Linearity and repeatability checks were used to validate the testing methodology in accordance with ISO guidelines. Additional validity checks were performed to improve the test setup and further increase the level of confidence in the experimental results. The natural frequencies found were compared to the computational model, and where necessary, recommendations for future modelling improvements were made. In the case of the first sub-assembly, discrepancy in natural frequency for certain modes was reduced from 12 % to less than 2%. An acceptable level of correlation was found between experimental and computational results for the second fuselage structure, with a discrepancy of less than 10 % observed for most natural frequencies. Certain natural frequencies showed variance above 30 %, and potential reasons for this discrepancy are discussed. The experimental results also provided a basis of comparison for the mode shapes predicted in a computational model constructed by other researchers, acting to further validate computational results. With a detailed experimental methodology formed, and reliable experimental results produced, the project can now progress to the next phase which involves the construction and testing of a complete half scale tail section.
URI for this recordhttp://hdl.handle.net/1974/28599
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