Modeling and Prediction of Vibration Environment in Aircraft Structures : Evaluation of Model Fidelity for an Aircraft Structure Excited by a Turbulent Boundary Layer

Sammanfattning

During aircraft operation, a harsh vibration environment is generated that can induce structural damage andreduce equipment reliability. Accurate prediction of this environment is therefore required to properly dimension the structure and ensure reliable operation of onboard equipment. This thesis concerns the vibration environment of a generic part of an aircraft structure subjected to a turbulent boundary layer excitation. It investigates how the predicted vibration environment is influenced by the level of detail in the modeling of thegeometry. This includes modeling of the correlation in the boundary layer excitation, which is based on ESDU 75021, and an investigation on how to model equipment and their attachments. At first, different modeling strategies were tested by replicating a public research article using modal analysis. Three models were subjected to a load based on ESDU 75021 and the response was retrieved in three positions for comparison. Five models in total were made of the aircraft structure and the structural response at the equipment was analyzed. The results show that in reference to the most detailed model, the models perform differently depending on which equipment is analyzed, the frequency range in question and if the main focus of the analysis is the amplitude or the details in the signal.