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Structural Dynamic Instability of Flutter in Flapping Wing MAV by Develop A Nonlinear Finite Element Method

Ghasemzadeh Shanjani, Mohammad Javad | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56785 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Hosseini Kordkheili, Ali; Malaek, Mohamad Bagher
  7. Abstract:
  8. The objective of this research is to model the wing structure of a flapping wing MAV and investigate structural dynamic behavior of its wing. in this research, to investigate and identify dynamic instabilities, modeling of the structure based on a nonlinear four-node plane element and aerodynamic modeling based on the strip theory in unsteady flow has been done, and by coupling these two models, the final model is formed. In the model of the wing structure, the displacement and changes angle inside the plane of the wing sections have been ignored and only outside the plane have been assumed for the degrees of freedom. In addition, the veins in the flapping wing have been omitted and the material of the wing has been considered uniform. Also, in this model, in addition to considering the geometrical nonlinearities of the structure due to large displacements, the relation between stress and strain in the material are also nonlinearly and viscoelastically modeled. finally, four models contain linear model, geometrical nonlinear model, material nonlinear model, and combined nonlinear model were created and compares. Based on the results of this research on the four mentioned models, only the geometric nonlinear model and the combined nonlinear model were stable, and the two others were unstable at different speeds and frequencies. In addition, the instabilities created in the twist angle and in the out of plane displacement did not happen at the same time necessarily. Also, the occurrence of stall can be seen in the results and in the jumps on the graphs, but this stagnation did not lead to dynamic instability necessarily. For continuing of this research, to increase the results accuracy, the inside-plane displacements should also be included in the calculations. Also, the aerodynamic model does not calculate the latteral force and moments on the wing and the flapping wing. In addition to increase the results accuracy, based on the developed code and model, other flapping MAVs can be modeled in the dimensions of insects, and after identifying their dynamic instabilities, by adding a controller, the occurrence of instability can be prevented
  9. Keywords:
  10. Unsteady Flow ; Nonlinear Finite Element Method ; Viscoelastic Material ; Flapping Wing ; Flutter ; Micro Air Vehicle (MAV)

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